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THE DIAGNOSIS: Pedunculated Lipofibroma

Histopathology confirmed a pedunculated/polypoid lesion with intradermal lobules of adipocytes/mature adipose tissue admixed with connective tissue bundles and vascular ectasias. Overlying epidermal acanthosis with slight papillomatosis and hyperkeratosis was present (Figure 1). Masson trichrome staining highlighted admixed collagen bundles (Figure 2). Verhoeff–van Gieson staining showed marked reduction in elastic fibers (Figure 3). Immunostaining was negative for smooth muscle actin and desmin. A diagnosis of pedunculated lipofibroma on the nose was made based on both clinical and histopathologic findings.

Pedunculated lipofibroma (or solitary lipofibroma) is the solitary form of nevus lipomatosus cutaneous superficialis (NLCS).⁷ First described by Hoffmann and Zurhelle¹ in 1921, NLCS is an uncommon benign hamartomatous cutaneous lesion/connective tissue nevus that also has a classic multiple form.^1-13 The etiology of NLCS remains unclear, but several theories have been proposed to explain its pathogenesis, including deposition of adipocytes secondary to degenerative changes in dermal connective tissue, focal/local heterotopic development of adipose tissue, and derivation from differentiating lipoblasts (preadipose tissue) originating from precursor vascular or perivascular cells.^2-13

Pedunculated lipofibroma usually develops during the third to sixth decades of life and manifests as a single cutaneous lesion with a smooth surface, often on a non–pelvic girdle location.^7-13 No particular predilection sites are noted, with lesions reported on the arm, axilla, back, upper thigh, knee, and sole.^5,12 There are rare reports of this type of NLCS on the ear, scalp, forehead, or eyelid.^7-11

In the classic form of NLCS, multiple cutaneous lesions are present at birth or develop within the first 2 to 3 decades of life.^2-6 Lesions consist of soft, nontender, pedunculated, flesh-colored or yellowish papules and nodules with a verrucoid or cerebriform surface that may later coalesce to form plaques.^2-6 Predilection sites include the pelvic girdle, buttocks, sacral and coccygeal regions, and upper posterior thighs, with a linear or zosteriform pattern of distribution.^2-6 Rarely, the classic form can arise in elderly patients and/or at an atypical anatomic location (eg, clitoris,³ shoulder,⁵ thorax,⁵ abdomen⁵) and can demonstrate extension of lesions across the midline.⁴ Rare cases of classic NLCS on the scalp² and face^3-6 have been reported, including lesions localized to the nose³ and chin⁴ and others extending from the right mandible to the neck⁵ and right lower lip to the submandibular/posteriorateral cervical region.⁶ In some cases, lesions clinically resemble plane xanthoma⁴ and localized scleroderma.⁶

Adotama et al¹³ proposed a set of clinical features to differentiate classic NLCS, pedunculated lipofibroma (solitary NLCS), and fibroepithelial polyp with adipocytes (distinguished by their furrowed surface, hyperpigmentation, and anatomic predilection for the neck and axilla). Lesions are asymptomatic in both forms of NLCS.^2-13 Family history or predominant sex involvement have not been reported in either clinical type.^2-13 Reported associations with NLCS include a number of endocrinologic conditions including diabetes.⁷ Other coexisting skin findings can include café-au-lait macules, leukodermic (white) spots, overlying hypertrichosis, comedolike alterations, angiokeratoma, hemangioma, and folliculosebaceous cystic hamartoma.⁴ None of these were evident in our patient.

Lesions from both types of NLCS are indistinguishable on histopathology, characterized by the presence of a central core of ectopic mature adipocytes in the papillary/reticular dermis.^2-13 Additional light microscopic features (some seen in our case) have been described, including thickened collagen bundles, reduction of elastic fibers, increased numbers of fibroblasts and/or mast cells, increased (small-vessel) vascularity, focal mucin deposition/myxoid degeneration, a mild perivascular lymphocytic infiltrate, attenuation of adnexal structures, and abnormalities of the epidermis (eg, surface ulceration).^2-13

Prior to biopsy, the differential diagnosis in our patient included angiofibroma, pyogenic granuloma, and basal cell carcinoma given the exophytic, pink, papular appearance of the lesion; however, the histopathologic differential diagnosis included angiofibroma, angiomyolipoma, lymphangioma, nevus sebaceus, and spindle cell lipoma (SCL). In angiofibroma, a dermal proliferation of stellate fibroblasts, dilated blood vessels, and collagenous stroma are seen. Cutaneous angiomyolipoma demonstrates smooth muscle bundles in addition to thickened blood vessels and variable proportions of mature adipocytes. Lymphangioma is characterized by dilated lymph channels lined by flat endothelial cells. Nevus sebaceus shows superficial immature and abnormally formed pilosebaceous units, with epidermal papillomatosis.

Rare cases of SCL on the nose have been described.¹⁴ Similar to pedunculated lipofibroma, reported examples demonstrate mature univacuolar adipocytes with thick collagen fibers and bland uniform spindle cells. Unlike the lesion seen in our patient, nasal SCL may be clinically mobile and typically is localized to the subcutaneous tissue, although dermal tumors also occur.¹⁴ Variably reported histopathologic findings in nasal SCL include circumscription/encapsulation, spindle cells arranged in short fascicles with nuclear palisading, a myxoid/mucinous interstitial matrix, and/or multinucleated giant cells—all light microscopic features that were not identified in our case; however, variable proportions of adipocytic, fibrous, and myxoid components among reported examples of SCL on the nose¹⁴ can make distinction from pedunculated lipofibroma difficult, as both are benign lipomatous tumor variants.

Clinically, pedunculated lipofibroma may be confused with more common benign cutaneous lesions and must be distinguished from other fibrolipomatous lesions on the nose. Specifically, the differential diagnosis includes benign cutaneous papillomas such as acrochordon, angiofibroma, melanocytic nevi, neurofibroma, nevus sebaceus, lymphangioma, and eccrine poroma.^7-13 These all can be readily excluded on histopathology. Pedunculated lipofibroma on the nose, as in our patient, must be distinguished from fibrolipoma¹⁵ and dendritic myxofibrolipoma.¹⁶ Fibrolipoma is a subcutaneous proliferation of mature adipose tissue and fibrous tissue and comprises 1.6% of all facial lipomas reported worldwide.¹⁵ Dendritic myxofibrolipoma is a recently described benign soft-tissue tumor characterized by an admixture of mature adipose tissue, spindle and stellate cells, and an abundant myxoid stroma with prominent collagenization.¹⁶

Treatment of pedunculated lipofibroma on the nose is not indicated except for cosmetic reasons, in which case simple surgical excision would be considered satisfactory. Following biopsy, no further treatment was pursued in our patient.

THE DIAGNOSIS: Pedunculated Lipofibroma

Histopathology confirmed a pedunculated/polypoid lesion with intradermal lobules of adipocytes/mature adipose tissue admixed with connective tissue bundles and vascular ectasias. Overlying epidermal acanthosis with slight papillomatosis and hyperkeratosis was present (Figure 1). Masson trichrome staining highlighted admixed collagen bundles (Figure 2). Verhoeff–van Gieson staining showed marked reduction in elastic fibers (Figure 3). Immunostaining was negative for smooth muscle actin and desmin. A diagnosis of pedunculated lipofibroma on the nose was made based on both clinical and histopathologic findings.

Pedunculated lipofibroma (or solitary lipofibroma) is the solitary form of nevus lipomatosus cutaneous superficialis (NLCS).⁷ First described by Hoffmann and Zurhelle¹ in 1921, NLCS is an uncommon benign hamartomatous cutaneous lesion/connective tissue nevus that also has a classic multiple form.^1-13 The etiology of NLCS remains unclear, but several theories have been proposed to explain its pathogenesis, including deposition of adipocytes secondary to degenerative changes in dermal connective tissue, focal/local heterotopic development of adipose tissue, and derivation from differentiating lipoblasts (preadipose tissue) originating from precursor vascular or perivascular cells.^2-13

Pedunculated lipofibroma usually develops during the third to sixth decades of life and manifests as a single cutaneous lesion with a smooth surface, often on a non–pelvic girdle location.^7-13 No particular predilection sites are noted, with lesions reported on the arm, axilla, back, upper thigh, knee, and sole.^5,12 There are rare reports of this type of NLCS on the ear, scalp, forehead, or eyelid.^7-11

In the classic form of NLCS, multiple cutaneous lesions are present at birth or develop within the first 2 to 3 decades of life.^2-6 Lesions consist of soft, nontender, pedunculated, flesh-colored or yellowish papules and nodules with a verrucoid or cerebriform surface that may later coalesce to form plaques.^2-6 Predilection sites include the pelvic girdle, buttocks, sacral and coccygeal regions, and upper posterior thighs, with a linear or zosteriform pattern of distribution.^2-6 Rarely, the classic form can arise in elderly patients and/or at an atypical anatomic location (eg, clitoris,³ shoulder,⁵ thorax,⁵ abdomen⁵) and can demonstrate extension of lesions across the midline.⁴ Rare cases of classic NLCS on the scalp² and face^3-6 have been reported, including lesions localized to the nose³ and chin⁴ and others extending from the right mandible to the neck⁵ and right lower lip to the submandibular/posteriorateral cervical region.⁶ In some cases, lesions clinically resemble plane xanthoma⁴ and localized scleroderma.⁶

Adotama et al¹³ proposed a set of clinical features to differentiate classic NLCS, pedunculated lipofibroma (solitary NLCS), and fibroepithelial polyp with adipocytes (distinguished by their furrowed surface, hyperpigmentation, and anatomic predilection for the neck and axilla). Lesions are asymptomatic in both forms of NLCS.^2-13 Family history or predominant sex involvement have not been reported in either clinical type.^2-13 Reported associations with NLCS include a number of endocrinologic conditions including diabetes.⁷ Other coexisting skin findings can include café-au-lait macules, leukodermic (white) spots, overlying hypertrichosis, comedolike alterations, angiokeratoma, hemangioma, and folliculosebaceous cystic hamartoma.⁴ None of these were evident in our patient.

Lesions from both types of NLCS are indistinguishable on histopathology, characterized by the presence of a central core of ectopic mature adipocytes in the papillary/reticular dermis.^2-13 Additional light microscopic features (some seen in our case) have been described, including thickened collagen bundles, reduction of elastic fibers, increased numbers of fibroblasts and/or mast cells, increased (small-vessel) vascularity, focal mucin deposition/myxoid degeneration, a mild perivascular lymphocytic infiltrate, attenuation of adnexal structures, and abnormalities of the epidermis (eg, surface ulceration).^2-13

Prior to biopsy, the differential diagnosis in our patient included angiofibroma, pyogenic granuloma, and basal cell carcinoma given the exophytic, pink, papular appearance of the lesion; however, the histopathologic differential diagnosis included angiofibroma, angiomyolipoma, lymphangioma, nevus sebaceus, and spindle cell lipoma (SCL). In angiofibroma, a dermal proliferation of stellate fibroblasts, dilated blood vessels, and collagenous stroma are seen. Cutaneous angiomyolipoma demonstrates smooth muscle bundles in addition to thickened blood vessels and variable proportions of mature adipocytes. Lymphangioma is characterized by dilated lymph channels lined by flat endothelial cells. Nevus sebaceus shows superficial immature and abnormally formed pilosebaceous units, with epidermal papillomatosis.

Rare cases of SCL on the nose have been described.¹⁴ Similar to pedunculated lipofibroma, reported examples demonstrate mature univacuolar adipocytes with thick collagen fibers and bland uniform spindle cells. Unlike the lesion seen in our patient, nasal SCL may be clinically mobile and typically is localized to the subcutaneous tissue, although dermal tumors also occur.¹⁴ Variably reported histopathologic findings in nasal SCL include circumscription/encapsulation, spindle cells arranged in short fascicles with nuclear palisading, a myxoid/mucinous interstitial matrix, and/or multinucleated giant cells—all light microscopic features that were not identified in our case; however, variable proportions of adipocytic, fibrous, and myxoid components among reported examples of SCL on the nose¹⁴ can make distinction from pedunculated lipofibroma difficult, as both are benign lipomatous tumor variants.

Clinically, pedunculated lipofibroma may be confused with more common benign cutaneous lesions and must be distinguished from other fibrolipomatous lesions on the nose. Specifically, the differential diagnosis includes benign cutaneous papillomas such as acrochordon, angiofibroma, melanocytic nevi, neurofibroma, nevus sebaceus, lymphangioma, and eccrine poroma.^7-13 These all can be readily excluded on histopathology. Pedunculated lipofibroma on the nose, as in our patient, must be distinguished from fibrolipoma¹⁵ and dendritic myxofibrolipoma.¹⁶ Fibrolipoma is a subcutaneous proliferation of mature adipose tissue and fibrous tissue and comprises 1.6% of all facial lipomas reported worldwide.¹⁵ Dendritic myxofibrolipoma is a recently described benign soft-tissue tumor characterized by an admixture of mature adipose tissue, spindle and stellate cells, and an abundant myxoid stroma with prominent collagenization.¹⁶

Treatment of pedunculated lipofibroma on the nose is not indicated except for cosmetic reasons, in which case simple surgical excision would be considered satisfactory. Following biopsy, no further treatment was pursued in our patient.

THE DIAGNOSIS: Pedunculated Lipofibroma

Histopathology confirmed a pedunculated/polypoid lesion with intradermal lobules of adipocytes/mature adipose tissue admixed with connective tissue bundles and vascular ectasias. Overlying epidermal acanthosis with slight papillomatosis and hyperkeratosis was present (Figure 1). Masson trichrome staining highlighted admixed collagen bundles (Figure 2). Verhoeff–van Gieson staining showed marked reduction in elastic fibers (Figure 3). Immunostaining was negative for smooth muscle actin and desmin. A diagnosis of pedunculated lipofibroma on the nose was made based on both clinical and histopathologic findings.

Pedunculated lipofibroma (or solitary lipofibroma) is the solitary form of nevus lipomatosus cutaneous superficialis (NLCS).⁷ First described by Hoffmann and Zurhelle¹ in 1921, NLCS is an uncommon benign hamartomatous cutaneous lesion/connective tissue nevus that also has a classic multiple form.^1-13 The etiology of NLCS remains unclear, but several theories have been proposed to explain its pathogenesis, including deposition of adipocytes secondary to degenerative changes in dermal connective tissue, focal/local heterotopic development of adipose tissue, and derivation from differentiating lipoblasts (preadipose tissue) originating from precursor vascular or perivascular cells.^2-13

Pedunculated lipofibroma usually develops during the third to sixth decades of life and manifests as a single cutaneous lesion with a smooth surface, often on a non–pelvic girdle location.^7-13 No particular predilection sites are noted, with lesions reported on the arm, axilla, back, upper thigh, knee, and sole.^5,12 There are rare reports of this type of NLCS on the ear, scalp, forehead, or eyelid.^7-11

In the classic form of NLCS, multiple cutaneous lesions are present at birth or develop within the first 2 to 3 decades of life.^2-6 Lesions consist of soft, nontender, pedunculated, flesh-colored or yellowish papules and nodules with a verrucoid or cerebriform surface that may later coalesce to form plaques.^2-6 Predilection sites include the pelvic girdle, buttocks, sacral and coccygeal regions, and upper posterior thighs, with a linear or zosteriform pattern of distribution.^2-6 Rarely, the classic form can arise in elderly patients and/or at an atypical anatomic location (eg, clitoris,³ shoulder,⁵ thorax,⁵ abdomen⁵) and can demonstrate extension of lesions across the midline.⁴ Rare cases of classic NLCS on the scalp² and face^3-6 have been reported, including lesions localized to the nose³ and chin⁴ and others extending from the right mandible to the neck⁵ and right lower lip to the submandibular/posteriorateral cervical region.⁶ In some cases, lesions clinically resemble plane xanthoma⁴ and localized scleroderma.⁶

Adotama et al¹³ proposed a set of clinical features to differentiate classic NLCS, pedunculated lipofibroma (solitary NLCS), and fibroepithelial polyp with adipocytes (distinguished by their furrowed surface, hyperpigmentation, and anatomic predilection for the neck and axilla). Lesions are asymptomatic in both forms of NLCS.^2-13 Family history or predominant sex involvement have not been reported in either clinical type.^2-13 Reported associations with NLCS include a number of endocrinologic conditions including diabetes.⁷ Other coexisting skin findings can include café-au-lait macules, leukodermic (white) spots, overlying hypertrichosis, comedolike alterations, angiokeratoma, hemangioma, and folliculosebaceous cystic hamartoma.⁴ None of these were evident in our patient.

Lesions from both types of NLCS are indistinguishable on histopathology, characterized by the presence of a central core of ectopic mature adipocytes in the papillary/reticular dermis.^2-13 Additional light microscopic features (some seen in our case) have been described, including thickened collagen bundles, reduction of elastic fibers, increased numbers of fibroblasts and/or mast cells, increased (small-vessel) vascularity, focal mucin deposition/myxoid degeneration, a mild perivascular lymphocytic infiltrate, attenuation of adnexal structures, and abnormalities of the epidermis (eg, surface ulceration).^2-13

Prior to biopsy, the differential diagnosis in our patient included angiofibroma, pyogenic granuloma, and basal cell carcinoma given the exophytic, pink, papular appearance of the lesion; however, the histopathologic differential diagnosis included angiofibroma, angiomyolipoma, lymphangioma, nevus sebaceus, and spindle cell lipoma (SCL). In angiofibroma, a dermal proliferation of stellate fibroblasts, dilated blood vessels, and collagenous stroma are seen. Cutaneous angiomyolipoma demonstrates smooth muscle bundles in addition to thickened blood vessels and variable proportions of mature adipocytes. Lymphangioma is characterized by dilated lymph channels lined by flat endothelial cells. Nevus sebaceus shows superficial immature and abnormally formed pilosebaceous units, with epidermal papillomatosis.

Rare cases of SCL on the nose have been described.¹⁴ Similar to pedunculated lipofibroma, reported examples demonstrate mature univacuolar adipocytes with thick collagen fibers and bland uniform spindle cells. Unlike the lesion seen in our patient, nasal SCL may be clinically mobile and typically is localized to the subcutaneous tissue, although dermal tumors also occur.¹⁴ Variably reported histopathologic findings in nasal SCL include circumscription/encapsulation, spindle cells arranged in short fascicles with nuclear palisading, a myxoid/mucinous interstitial matrix, and/or multinucleated giant cells—all light microscopic features that were not identified in our case; however, variable proportions of adipocytic, fibrous, and myxoid components among reported examples of SCL on the nose¹⁴ can make distinction from pedunculated lipofibroma difficult, as both are benign lipomatous tumor variants.

Clinically, pedunculated lipofibroma may be confused with more common benign cutaneous lesions and must be distinguished from other fibrolipomatous lesions on the nose. Specifically, the differential diagnosis includes benign cutaneous papillomas such as acrochordon, angiofibroma, melanocytic nevi, neurofibroma, nevus sebaceus, lymphangioma, and eccrine poroma.^7-13 These all can be readily excluded on histopathology. Pedunculated lipofibroma on the nose, as in our patient, must be distinguished from fibrolipoma¹⁵ and dendritic myxofibrolipoma.¹⁶ Fibrolipoma is a subcutaneous proliferation of mature adipose tissue and fibrous tissue and comprises 1.6% of all facial lipomas reported worldwide.¹⁵ Dendritic myxofibrolipoma is a recently described benign soft-tissue tumor characterized by an admixture of mature adipose tissue, spindle and stellate cells, and an abundant myxoid stroma with prominent collagenization.¹⁶

Treatment of pedunculated lipofibroma on the nose is not indicated except for cosmetic reasons, in which case simple surgical excision would be considered satisfactory. Following biopsy, no further treatment was pursued in our patient.

The Diagnosis: Allergic Contact Dermatitis

In our patient, the erythematous pruritic rash on the face and neck, the lack of systemic symptoms, and her history of atopic dermatitis suggested a diagnosis of allergic contact dermatitis (ACD). She underwent patch testing with standard, fragrance, and cosmetic panels in addition to 6 of her personal care products. Her first patch test, which was read on day 2, showed a positive reaction to isopropyl myristate (IPM), a penetration enhancer used in cosmetics, topical medications (eg, tretinoin), and cosmeceuticals. The reading on day 5 showed a 2+ reaction to IPM, which was found in several of her personal care products, including her shampoo, leave-in conditioner, and eczema-calming cream. Isopropyl myristate is used in these products because of its ability to enhance their penetration into the skin and also can be found in commercially used products such as hand sanitizers. The patient was given information on this allergen and how to identify and avoid triggers. At follow-up, the ACD had resolved with avoidance of IPM. 

Contact dermatitis is an inflammatory skin condition that is triggered by contact with a specific causative agent. There are 2 types of contact dermatitis: irritant and allergic; the irritant type is more common (approximately 80% of cases worldwide).¹ Allergic contact dermatitis is a type IV (delayed-type) hypersensitivity reaction; common causative agents include shampoos, moisturizers, makeup, certain metals (eg, nickel), fragrances, latex, and certain plants (eg, poison ivy).² In cases of ACD, a new reaction can develop from exposure to a product that the patient has used for years. It manifests clinically as erythema, pruritus, scaling, and vesicle formation.¹ Certain populations, such as those with atopic dermatitis, are more prone to developing ACD due to a breakdown of the skin barrier, frequent use of topical products, and immune dysregulation.^1,2 Patch testing performed by dermatologists and allergists is the gold standard for diagnosing ACD.^1,3 

Annually, allergists, dermatologists, and primary care physicians see thousands of cases of contact dermatitis.¹ Early recognition and appropriate treatment can help reduce the severity and duration of symptoms and improve patient outcomes. The main treatment for ACD is identification of the causative agent followed by patient education on how to identify and avoid triggers.² Once patch testing has been completed, patients can be given access to the American Contact Dermatitis Society’s Contact Allergen Management Program (CAMP) database (https://www.contactderm.org/resources/acds-camp) to help them identify and avoid products that contain triggering allergens. 

Topical corticosteroids are the first-line pharmacologic treatments for atopic dermatitis.⁴ When our patient presented with the facial rash, her atopic dermatitis had been well controlled with both dupilumab and topical triamcinolone. The lack of response to previously successful therapies in a new area of involvement made a flare of atopic dermatitis less likely. For flares of ACD after exposure, topical corticosteroids and topical calcineurin inhibitors can help. If needed due to severity, oral corticosteroids also can be used.¹ 

Dermatomyositis is an inflammatory myopathy that has several skin manifestations, including a heliotrope rash and poikiloderma.⁵ While our patient’s rash covered the periorbital area, she did not have other classic skin findings of dermatomyositis, such as nail-fold capillary changes or poikiloderma in a shawl or holster distribution.⁶ She also lacked signs of systemic involvement including myositis and elevated C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and creatine kinase levels.⁵ 

Erythematotelangiectatic rosacea is characterized by telangiectasias and transient flushing and erythema on the central face.⁵ Rosacea typically is triggered by temperature changes, alcohol consumption, sun exposure, spicy foods, and stress⁵ and would be expected to involve the nose, which was not observed in our patient. The fixed nature of our patient’s patches and the absence of telangiectasias also argued against this diagnosis. 

The classic cutaneous finding of systemic lupus erythematosus is a malar rash, which appears as erythematous patches or thin plaques across the bridge of the nose and over the cheeks, sparing the nasolabial folds.5 Systemic lupus erythematosus is associated with laboratory abnormalities, such as positive antinuclear antibodies and elevated CRP and ESR levels.⁵ Our patient had notable sparing of the nose, negative antinuclear antibodies, and normal CRP and ESR levels, making systemic lupus erythematosus unlikely. Systemic lupus erythematosus also can manifest with photosensitivity,⁷ and involvement of the submental skin in our patient argued against a photosensitive eruption.

The Diagnosis: Allergic Contact Dermatitis

In our patient, the erythematous pruritic rash on the face and neck, the lack of systemic symptoms, and her history of atopic dermatitis suggested a diagnosis of allergic contact dermatitis (ACD). She underwent patch testing with standard, fragrance, and cosmetic panels in addition to 6 of her personal care products. Her first patch test, which was read on day 2, showed a positive reaction to isopropyl myristate (IPM), a penetration enhancer used in cosmetics, topical medications (eg, tretinoin), and cosmeceuticals. The reading on day 5 showed a 2+ reaction to IPM, which was found in several of her personal care products, including her shampoo, leave-in conditioner, and eczema-calming cream. Isopropyl myristate is used in these products because of its ability to enhance their penetration into the skin and also can be found in commercially used products such as hand sanitizers. The patient was given information on this allergen and how to identify and avoid triggers. At follow-up, the ACD had resolved with avoidance of IPM. 

Contact dermatitis is an inflammatory skin condition that is triggered by contact with a specific causative agent. There are 2 types of contact dermatitis: irritant and allergic; the irritant type is more common (approximately 80% of cases worldwide).¹ Allergic contact dermatitis is a type IV (delayed-type) hypersensitivity reaction; common causative agents include shampoos, moisturizers, makeup, certain metals (eg, nickel), fragrances, latex, and certain plants (eg, poison ivy).² In cases of ACD, a new reaction can develop from exposure to a product that the patient has used for years. It manifests clinically as erythema, pruritus, scaling, and vesicle formation.¹ Certain populations, such as those with atopic dermatitis, are more prone to developing ACD due to a breakdown of the skin barrier, frequent use of topical products, and immune dysregulation.^1,2 Patch testing performed by dermatologists and allergists is the gold standard for diagnosing ACD.^1,3 

Annually, allergists, dermatologists, and primary care physicians see thousands of cases of contact dermatitis.¹ Early recognition and appropriate treatment can help reduce the severity and duration of symptoms and improve patient outcomes. The main treatment for ACD is identification of the causative agent followed by patient education on how to identify and avoid triggers.² Once patch testing has been completed, patients can be given access to the American Contact Dermatitis Society’s Contact Allergen Management Program (CAMP) database (https://www.contactderm.org/resources/acds-camp) to help them identify and avoid products that contain triggering allergens. 

Topical corticosteroids are the first-line pharmacologic treatments for atopic dermatitis.⁴ When our patient presented with the facial rash, her atopic dermatitis had been well controlled with both dupilumab and topical triamcinolone. The lack of response to previously successful therapies in a new area of involvement made a flare of atopic dermatitis less likely. For flares of ACD after exposure, topical corticosteroids and topical calcineurin inhibitors can help. If needed due to severity, oral corticosteroids also can be used.¹ 

Dermatomyositis is an inflammatory myopathy that has several skin manifestations, including a heliotrope rash and poikiloderma.⁵ While our patient’s rash covered the periorbital area, she did not have other classic skin findings of dermatomyositis, such as nail-fold capillary changes or poikiloderma in a shawl or holster distribution.⁶ She also lacked signs of systemic involvement including myositis and elevated C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and creatine kinase levels.⁵ 

Erythematotelangiectatic rosacea is characterized by telangiectasias and transient flushing and erythema on the central face.⁵ Rosacea typically is triggered by temperature changes, alcohol consumption, sun exposure, spicy foods, and stress⁵ and would be expected to involve the nose, which was not observed in our patient. The fixed nature of our patient’s patches and the absence of telangiectasias also argued against this diagnosis. 

The classic cutaneous finding of systemic lupus erythematosus is a malar rash, which appears as erythematous patches or thin plaques across the bridge of the nose and over the cheeks, sparing the nasolabial folds.5 Systemic lupus erythematosus is associated with laboratory abnormalities, such as positive antinuclear antibodies and elevated CRP and ESR levels.⁵ Our patient had notable sparing of the nose, negative antinuclear antibodies, and normal CRP and ESR levels, making systemic lupus erythematosus unlikely. Systemic lupus erythematosus also can manifest with photosensitivity,⁷ and involvement of the submental skin in our patient argued against a photosensitive eruption.

The Diagnosis: Allergic Contact Dermatitis

In our patient, the erythematous pruritic rash on the face and neck, the lack of systemic symptoms, and her history of atopic dermatitis suggested a diagnosis of allergic contact dermatitis (ACD). She underwent patch testing with standard, fragrance, and cosmetic panels in addition to 6 of her personal care products. Her first patch test, which was read on day 2, showed a positive reaction to isopropyl myristate (IPM), a penetration enhancer used in cosmetics, topical medications (eg, tretinoin), and cosmeceuticals. The reading on day 5 showed a 2+ reaction to IPM, which was found in several of her personal care products, including her shampoo, leave-in conditioner, and eczema-calming cream. Isopropyl myristate is used in these products because of its ability to enhance their penetration into the skin and also can be found in commercially used products such as hand sanitizers. The patient was given information on this allergen and how to identify and avoid triggers. At follow-up, the ACD had resolved with avoidance of IPM. 

Contact dermatitis is an inflammatory skin condition that is triggered by contact with a specific causative agent. There are 2 types of contact dermatitis: irritant and allergic; the irritant type is more common (approximately 80% of cases worldwide).¹ Allergic contact dermatitis is a type IV (delayed-type) hypersensitivity reaction; common causative agents include shampoos, moisturizers, makeup, certain metals (eg, nickel), fragrances, latex, and certain plants (eg, poison ivy).² In cases of ACD, a new reaction can develop from exposure to a product that the patient has used for years. It manifests clinically as erythema, pruritus, scaling, and vesicle formation.¹ Certain populations, such as those with atopic dermatitis, are more prone to developing ACD due to a breakdown of the skin barrier, frequent use of topical products, and immune dysregulation.^1,2 Patch testing performed by dermatologists and allergists is the gold standard for diagnosing ACD.^1,3 

Annually, allergists, dermatologists, and primary care physicians see thousands of cases of contact dermatitis.¹ Early recognition and appropriate treatment can help reduce the severity and duration of symptoms and improve patient outcomes. The main treatment for ACD is identification of the causative agent followed by patient education on how to identify and avoid triggers.² Once patch testing has been completed, patients can be given access to the American Contact Dermatitis Society’s Contact Allergen Management Program (CAMP) database (https://www.contactderm.org/resources/acds-camp) to help them identify and avoid products that contain triggering allergens. 

Topical corticosteroids are the first-line pharmacologic treatments for atopic dermatitis.⁴ When our patient presented with the facial rash, her atopic dermatitis had been well controlled with both dupilumab and topical triamcinolone. The lack of response to previously successful therapies in a new area of involvement made a flare of atopic dermatitis less likely. For flares of ACD after exposure, topical corticosteroids and topical calcineurin inhibitors can help. If needed due to severity, oral corticosteroids also can be used.¹ 

Dermatomyositis is an inflammatory myopathy that has several skin manifestations, including a heliotrope rash and poikiloderma.⁵ While our patient’s rash covered the periorbital area, she did not have other classic skin findings of dermatomyositis, such as nail-fold capillary changes or poikiloderma in a shawl or holster distribution.⁶ She also lacked signs of systemic involvement including myositis and elevated C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and creatine kinase levels.⁵ 

Erythematotelangiectatic rosacea is characterized by telangiectasias and transient flushing and erythema on the central face.⁵ Rosacea typically is triggered by temperature changes, alcohol consumption, sun exposure, spicy foods, and stress⁵ and would be expected to involve the nose, which was not observed in our patient. The fixed nature of our patient’s patches and the absence of telangiectasias also argued against this diagnosis. 

The classic cutaneous finding of systemic lupus erythematosus is a malar rash, which appears as erythematous patches or thin plaques across the bridge of the nose and over the cheeks, sparing the nasolabial folds.5 Systemic lupus erythematosus is associated with laboratory abnormalities, such as positive antinuclear antibodies and elevated CRP and ESR levels.⁵ Our patient had notable sparing of the nose, negative antinuclear antibodies, and normal CRP and ESR levels, making systemic lupus erythematosus unlikely. Systemic lupus erythematosus also can manifest with photosensitivity,⁷ and involvement of the submental skin in our patient argued against a photosensitive eruption.

THE DIAGNOSIS: Mpox

Histologic examination demonstrated dense aggregates of necrotic cellular debris composed of karyorrhectic nuclear fragments intermixed with neutrophils, lymphocytes, and histiocytes. Eosinophilic intracytoplasmic inclusions also were observed (Figure 1). The bacterial, fungal, and mycobacterial histologic special stains and cultures were negative. Three weeks after the initial visit with dermatology, the patient was admitted to the hospital for worsening symptoms of fever, chills, and painful erythema surrounding the skin lesions. Serology and viral workup revealed a positive mpox polymerase chain reaction test, suggesting a diagnosis of mpox. Following the Centers for Disease Control and Prevention protocol, the patient was started on oral tecovirimat 200 mg twice daily for 3 weeks and intravenous infusions of cidofovir 345 mg once weekly for 2 weeks. After treatment was initiated, the skin lesions showed rapid improvement (Figure 2), and he was discharged from the hospital after finishing the second dose of cidofovir. Four months after the initial dermatology consultation, the lesions had resolved completely with residual scarring. At that time, the patient had full movement of the right eye.

Mpox virus is a member of the Poxviridae family of zoonotic viruses, which are transmitted from animals to humans. The mpox virus is brick-shaped (rectangular) and has a genome of linear double-stranded DNA encoding 180 proteins.¹ Primates and rodents are the typical host reservoirs for viral circulation of mpox.² Animal-to-human transmission occurs through direct contact with mucous membranes, bodily fluids, or tissues of an infected animal. Human-to-human transmission occurs through direct contact with infected mucous membranes, bodily fluids, respiratory droplets, and contaminated fomites.²

Symptoms typically occur within 1 week of exposure to the mpox virus. Prodromal symptoms of fever, sore throat, body aches, and headaches last for 3 days.¹ Many patients experience a facial rash that spreads to the arms and legs over a period of 2 to 4 weeks. The rash initially manifests as small papules that progress to painful pustules and vesicles measuring 0.5 to 1.0 cm in diameter.³ The mpox virus is transmitted through these skin lesions until they crust over and re-epithelialize.¹ The case fatality rate for mpox infection remains low (0.18%).⁴

Mpox outbreaks mainly were limited to central and western Africa prior to 2022. From May 17, 2022, through October 6, 2022, 26,384 cases of mpox were reported in the United States.⁵ During this outbreak, immunocompromised patients diagnosed with HIV and men who have sex with men were disproportionately affected.⁵

Due to the similarities between the smallpox virus and other orthopoxviruses, certain smallpox vaccines have been indicated for pre-exposure prophylaxis.⁶ The efficacy of prophylactic vaccination is believed to stem from the production of neutralizing antibodies that are cross-protective against other orthopoxviruses, including mpox.⁷ The 2 vaccines approved in the United States for mpox prophylaxis are JYNNEOS and ACAM2000, which are both live attenuated vaccines. Pre-exposure prophylaxis is indicated for patients at risk for severe disease, including men who have sex with men, individuals diagnosed with HIV or other immunosuppressive disorders, and individuals with recent diagnoses of one or more sexually transmitted diseases.⁸

Most mpox cases resolve within 2 to 4 weeks and only require supportive care (eg, nonsteroidal anti-inflammatory drugs, topical steroids, topical anesthetics) to treat pain.⁸ For patients at risk for severe disease, antiviral medications are warranted. Tecovirimat, brincidofovir, and cidofovir are antiviral medications used to treat smallpox that are thought to be effective against mpox.^8,9 Tecovirimat and cidofovir have been shown to be effective against mpox in animal trials, but randomized or nonrandomized trials have not been performed in humans.^9-11 Tecovirimat currently is available for the treatment of severe mpox in patients who meet the Centers for Disease Control and Prevention’s Investigational New Drug protocol; for these patients, a 200-mg course is administered orally or intravenously every 12 hours for 2 weeks.⁸

THE DIAGNOSIS: Mpox

Histologic examination demonstrated dense aggregates of necrotic cellular debris composed of karyorrhectic nuclear fragments intermixed with neutrophils, lymphocytes, and histiocytes. Eosinophilic intracytoplasmic inclusions also were observed (Figure 1). The bacterial, fungal, and mycobacterial histologic special stains and cultures were negative. Three weeks after the initial visit with dermatology, the patient was admitted to the hospital for worsening symptoms of fever, chills, and painful erythema surrounding the skin lesions. Serology and viral workup revealed a positive mpox polymerase chain reaction test, suggesting a diagnosis of mpox. Following the Centers for Disease Control and Prevention protocol, the patient was started on oral tecovirimat 200 mg twice daily for 3 weeks and intravenous infusions of cidofovir 345 mg once weekly for 2 weeks. After treatment was initiated, the skin lesions showed rapid improvement (Figure 2), and he was discharged from the hospital after finishing the second dose of cidofovir. Four months after the initial dermatology consultation, the lesions had resolved completely with residual scarring. At that time, the patient had full movement of the right eye.

Mpox virus is a member of the Poxviridae family of zoonotic viruses, which are transmitted from animals to humans. The mpox virus is brick-shaped (rectangular) and has a genome of linear double-stranded DNA encoding 180 proteins.¹ Primates and rodents are the typical host reservoirs for viral circulation of mpox.² Animal-to-human transmission occurs through direct contact with mucous membranes, bodily fluids, or tissues of an infected animal. Human-to-human transmission occurs through direct contact with infected mucous membranes, bodily fluids, respiratory droplets, and contaminated fomites.²

Symptoms typically occur within 1 week of exposure to the mpox virus. Prodromal symptoms of fever, sore throat, body aches, and headaches last for 3 days.¹ Many patients experience a facial rash that spreads to the arms and legs over a period of 2 to 4 weeks. The rash initially manifests as small papules that progress to painful pustules and vesicles measuring 0.5 to 1.0 cm in diameter.³ The mpox virus is transmitted through these skin lesions until they crust over and re-epithelialize.¹ The case fatality rate for mpox infection remains low (0.18%).⁴

Mpox outbreaks mainly were limited to central and western Africa prior to 2022. From May 17, 2022, through October 6, 2022, 26,384 cases of mpox were reported in the United States.⁵ During this outbreak, immunocompromised patients diagnosed with HIV and men who have sex with men were disproportionately affected.⁵

Due to the similarities between the smallpox virus and other orthopoxviruses, certain smallpox vaccines have been indicated for pre-exposure prophylaxis.⁶ The efficacy of prophylactic vaccination is believed to stem from the production of neutralizing antibodies that are cross-protective against other orthopoxviruses, including mpox.⁷ The 2 vaccines approved in the United States for mpox prophylaxis are JYNNEOS and ACAM2000, which are both live attenuated vaccines. Pre-exposure prophylaxis is indicated for patients at risk for severe disease, including men who have sex with men, individuals diagnosed with HIV or other immunosuppressive disorders, and individuals with recent diagnoses of one or more sexually transmitted diseases.⁸

Most mpox cases resolve within 2 to 4 weeks and only require supportive care (eg, nonsteroidal anti-inflammatory drugs, topical steroids, topical anesthetics) to treat pain.⁸ For patients at risk for severe disease, antiviral medications are warranted. Tecovirimat, brincidofovir, and cidofovir are antiviral medications used to treat smallpox that are thought to be effective against mpox.^8,9 Tecovirimat and cidofovir have been shown to be effective against mpox in animal trials, but randomized or nonrandomized trials have not been performed in humans.^9-11 Tecovirimat currently is available for the treatment of severe mpox in patients who meet the Centers for Disease Control and Prevention’s Investigational New Drug protocol; for these patients, a 200-mg course is administered orally or intravenously every 12 hours for 2 weeks.⁸

THE DIAGNOSIS: Mpox

Histologic examination demonstrated dense aggregates of necrotic cellular debris composed of karyorrhectic nuclear fragments intermixed with neutrophils, lymphocytes, and histiocytes. Eosinophilic intracytoplasmic inclusions also were observed (Figure 1). The bacterial, fungal, and mycobacterial histologic special stains and cultures were negative. Three weeks after the initial visit with dermatology, the patient was admitted to the hospital for worsening symptoms of fever, chills, and painful erythema surrounding the skin lesions. Serology and viral workup revealed a positive mpox polymerase chain reaction test, suggesting a diagnosis of mpox. Following the Centers for Disease Control and Prevention protocol, the patient was started on oral tecovirimat 200 mg twice daily for 3 weeks and intravenous infusions of cidofovir 345 mg once weekly for 2 weeks. After treatment was initiated, the skin lesions showed rapid improvement (Figure 2), and he was discharged from the hospital after finishing the second dose of cidofovir. Four months after the initial dermatology consultation, the lesions had resolved completely with residual scarring. At that time, the patient had full movement of the right eye.

Mpox virus is a member of the Poxviridae family of zoonotic viruses, which are transmitted from animals to humans. The mpox virus is brick-shaped (rectangular) and has a genome of linear double-stranded DNA encoding 180 proteins.¹ Primates and rodents are the typical host reservoirs for viral circulation of mpox.² Animal-to-human transmission occurs through direct contact with mucous membranes, bodily fluids, or tissues of an infected animal. Human-to-human transmission occurs through direct contact with infected mucous membranes, bodily fluids, respiratory droplets, and contaminated fomites.²

Symptoms typically occur within 1 week of exposure to the mpox virus. Prodromal symptoms of fever, sore throat, body aches, and headaches last for 3 days.¹ Many patients experience a facial rash that spreads to the arms and legs over a period of 2 to 4 weeks. The rash initially manifests as small papules that progress to painful pustules and vesicles measuring 0.5 to 1.0 cm in diameter.³ The mpox virus is transmitted through these skin lesions until they crust over and re-epithelialize.¹ The case fatality rate for mpox infection remains low (0.18%).⁴

Mpox outbreaks mainly were limited to central and western Africa prior to 2022. From May 17, 2022, through October 6, 2022, 26,384 cases of mpox were reported in the United States.⁵ During this outbreak, immunocompromised patients diagnosed with HIV and men who have sex with men were disproportionately affected.⁵

Due to the similarities between the smallpox virus and other orthopoxviruses, certain smallpox vaccines have been indicated for pre-exposure prophylaxis.⁶ The efficacy of prophylactic vaccination is believed to stem from the production of neutralizing antibodies that are cross-protective against other orthopoxviruses, including mpox.⁷ The 2 vaccines approved in the United States for mpox prophylaxis are JYNNEOS and ACAM2000, which are both live attenuated vaccines. Pre-exposure prophylaxis is indicated for patients at risk for severe disease, including men who have sex with men, individuals diagnosed with HIV or other immunosuppressive disorders, and individuals with recent diagnoses of one or more sexually transmitted diseases.⁸

Most mpox cases resolve within 2 to 4 weeks and only require supportive care (eg, nonsteroidal anti-inflammatory drugs, topical steroids, topical anesthetics) to treat pain.⁸ For patients at risk for severe disease, antiviral medications are warranted. Tecovirimat, brincidofovir, and cidofovir are antiviral medications used to treat smallpox that are thought to be effective against mpox.^8,9 Tecovirimat and cidofovir have been shown to be effective against mpox in animal trials, but randomized or nonrandomized trials have not been performed in humans.^9-11 Tecovirimat currently is available for the treatment of severe mpox in patients who meet the Centers for Disease Control and Prevention’s Investigational New Drug protocol; for these patients, a 200-mg course is administered orally or intravenously every 12 hours for 2 weeks.⁸

THE DIAGNOSIS: Acral Eruptive Syringoma

Syringomas are small, benign, often asymptomatic eccrine tumors that originate in the intraepidermal portion of eccrine sweat ducts.¹ Clinically, they present as multiple symmetric white-to-yellow or discrete flesh-colored papules measuring 1 to 3 mm in diameter, often located on the face (most commonly on the eyelids), with a greater prevalence in middle-aged women. Occasionally, they manifest in other locations such as the cheeks, chest, axillae, abdomen, and groin.²

In 1987, Friedman and Butler³ developed a classification system categorizing syringomas into 4 clinical subtypes: familial syringoma, localized syringoma, Down syndrome–related syringoma, and generalized syringoma. The fourth subtype includes the variant of eruptive syringoma,³ a rare clinical manifestation that often develops before or during puberty with several flesh-colored or lightly pigmented papules on the neck, anterior chest, upper abdomen, axillae, periumbilical region, and/or genital region.^1,4,5 The etiology of eruptive syringomas is unclear, although it has been linked to abnormal proliferation of sweat glands due to an underlying local inflammatory process.⁶

Acral distribution of syringomas is a rare variant that can manifest as part of generalized eruptive syringoma with consequent involvement of the arms and other areas.^5,7 There are limited case reports on eruptive syringomas with predominant acral distribution.⁸ Compared to classic syringomas, the acral variant is associated with an older age of onset as well as a similar prevalence between men and women.⁹ Acral eruptive syringoma (AES) usually is isolated to the distal arms and legs. The most commonly affected region is the anterior surface of the forearms, although involvement of the dorsal hands, wrists, and feet also has been reported.^10-16

The first known case of AES, which was reported in 1977, described eruptive syringomas on the dorsal hands of a healthy 31-year-old man.¹⁷ Several cases have been reported since then, mostly in patients aged 30 to 60 years, with predominant involvement of the dorsal hands and forearms.^18-24 A review of Embase as well as PubMed articles indexed for MEDLINE using the search terms syringoma OR eccrine ductal tumor and eruptive OR acral OR arms OR forearms OR extremities identified 19 reported cases of AES between 1977 and 2023. For the reported AES cases, the mean (SD) age at diagnosis was 45.1 years (15.96 years), with patient ages ranging from 19 to 76 years. Notably, most cases occurred in individuals aged between 30 and 60 years, which deviates from the typical age of onset of localized syringomas, commonly seen during puberty or early adulthood.

Currently, AES is categorized within the clinical presentation of eruptive syringoma. Nevertheless, some authors have proposed classifying it as a distinct fifth clinical group due to specific features that distinguish it from generalized eruptive syringoma.⁹ This reclassification has considerable implications for the differential diagnosis, particularly because exclusive acral involvement poses a substantial diagnostic challenge and often requires histologic confirmation.

As shown in the Figure, histopathologic examination revealed tubular structures in the upper dermis with characteristic comma-shaped extensions. Some of these structures were lined with cuboidal cells and contained eosinophilic material within the lumen. There was no involvement of the epidermis or deeper dermis. The histologic features were consistent with syringoma, which is distinguished by its predominant involvement of the upper dermis and the presence of enlarged, dilated eccrine ducts, as observed in our case.

Treatment of syringomas often is challenging due to the high rate of recurrence and the risk for postinflammatory hyperpigmentation. Since the condition is benign, treatment typically is pursued for aesthetic reasons. Various therapeutic approaches have been reported, each with diverse response rates. The most common method involves surgical intervention, either with electrodesiccation or CO₂ laser—both of which have shown satisfactory resolution of lesions without recurrence at 1-year follow-up, with no major scarring reported.^25,26 Alternatively, topical management with retinoids daily over a 4-month period leads to flattening of the tumors with no further appearance of new lesions.²⁷ Despite the availability of numerous management options, establishing a first-line treatment remains controversial due to the high risk for recurrence and the variability in the number and location of lesions among individual patients. In our case, given the benign nature of syringomas, the asymptomatic nature of the lesions, the involvement of noncritical aesthetic areas, and the limited response to noninvasive therapeutic options, the patient was informed of the diagnosis, and no further pharmacologic or surgical intervention was pursued.

THE DIAGNOSIS: Acral Eruptive Syringoma

Syringomas are small, benign, often asymptomatic eccrine tumors that originate in the intraepidermal portion of eccrine sweat ducts.¹ Clinically, they present as multiple symmetric white-to-yellow or discrete flesh-colored papules measuring 1 to 3 mm in diameter, often located on the face (most commonly on the eyelids), with a greater prevalence in middle-aged women. Occasionally, they manifest in other locations such as the cheeks, chest, axillae, abdomen, and groin.²

In 1987, Friedman and Butler³ developed a classification system categorizing syringomas into 4 clinical subtypes: familial syringoma, localized syringoma, Down syndrome–related syringoma, and generalized syringoma. The fourth subtype includes the variant of eruptive syringoma,³ a rare clinical manifestation that often develops before or during puberty with several flesh-colored or lightly pigmented papules on the neck, anterior chest, upper abdomen, axillae, periumbilical region, and/or genital region.^1,4,5 The etiology of eruptive syringomas is unclear, although it has been linked to abnormal proliferation of sweat glands due to an underlying local inflammatory process.⁶

Acral distribution of syringomas is a rare variant that can manifest as part of generalized eruptive syringoma with consequent involvement of the arms and other areas.^5,7 There are limited case reports on eruptive syringomas with predominant acral distribution.⁸ Compared to classic syringomas, the acral variant is associated with an older age of onset as well as a similar prevalence between men and women.⁹ Acral eruptive syringoma (AES) usually is isolated to the distal arms and legs. The most commonly affected region is the anterior surface of the forearms, although involvement of the dorsal hands, wrists, and feet also has been reported.^10-16

The first known case of AES, which was reported in 1977, described eruptive syringomas on the dorsal hands of a healthy 31-year-old man.¹⁷ Several cases have been reported since then, mostly in patients aged 30 to 60 years, with predominant involvement of the dorsal hands and forearms.^18-24 A review of Embase as well as PubMed articles indexed for MEDLINE using the search terms syringoma OR eccrine ductal tumor and eruptive OR acral OR arms OR forearms OR extremities identified 19 reported cases of AES between 1977 and 2023. For the reported AES cases, the mean (SD) age at diagnosis was 45.1 years (15.96 years), with patient ages ranging from 19 to 76 years. Notably, most cases occurred in individuals aged between 30 and 60 years, which deviates from the typical age of onset of localized syringomas, commonly seen during puberty or early adulthood.

Currently, AES is categorized within the clinical presentation of eruptive syringoma. Nevertheless, some authors have proposed classifying it as a distinct fifth clinical group due to specific features that distinguish it from generalized eruptive syringoma.⁹ This reclassification has considerable implications for the differential diagnosis, particularly because exclusive acral involvement poses a substantial diagnostic challenge and often requires histologic confirmation.

As shown in the Figure, histopathologic examination revealed tubular structures in the upper dermis with characteristic comma-shaped extensions. Some of these structures were lined with cuboidal cells and contained eosinophilic material within the lumen. There was no involvement of the epidermis or deeper dermis. The histologic features were consistent with syringoma, which is distinguished by its predominant involvement of the upper dermis and the presence of enlarged, dilated eccrine ducts, as observed in our case.

Treatment of syringomas often is challenging due to the high rate of recurrence and the risk for postinflammatory hyperpigmentation. Since the condition is benign, treatment typically is pursued for aesthetic reasons. Various therapeutic approaches have been reported, each with diverse response rates. The most common method involves surgical intervention, either with electrodesiccation or CO₂ laser—both of which have shown satisfactory resolution of lesions without recurrence at 1-year follow-up, with no major scarring reported.^25,26 Alternatively, topical management with retinoids daily over a 4-month period leads to flattening of the tumors with no further appearance of new lesions.²⁷ Despite the availability of numerous management options, establishing a first-line treatment remains controversial due to the high risk for recurrence and the variability in the number and location of lesions among individual patients. In our case, given the benign nature of syringomas, the asymptomatic nature of the lesions, the involvement of noncritical aesthetic areas, and the limited response to noninvasive therapeutic options, the patient was informed of the diagnosis, and no further pharmacologic or surgical intervention was pursued.

THE DIAGNOSIS: Acral Eruptive Syringoma

Syringomas are small, benign, often asymptomatic eccrine tumors that originate in the intraepidermal portion of eccrine sweat ducts.¹ Clinically, they present as multiple symmetric white-to-yellow or discrete flesh-colored papules measuring 1 to 3 mm in diameter, often located on the face (most commonly on the eyelids), with a greater prevalence in middle-aged women. Occasionally, they manifest in other locations such as the cheeks, chest, axillae, abdomen, and groin.²

In 1987, Friedman and Butler³ developed a classification system categorizing syringomas into 4 clinical subtypes: familial syringoma, localized syringoma, Down syndrome–related syringoma, and generalized syringoma. The fourth subtype includes the variant of eruptive syringoma,³ a rare clinical manifestation that often develops before or during puberty with several flesh-colored or lightly pigmented papules on the neck, anterior chest, upper abdomen, axillae, periumbilical region, and/or genital region.^1,4,5 The etiology of eruptive syringomas is unclear, although it has been linked to abnormal proliferation of sweat glands due to an underlying local inflammatory process.⁶

Acral distribution of syringomas is a rare variant that can manifest as part of generalized eruptive syringoma with consequent involvement of the arms and other areas.^5,7 There are limited case reports on eruptive syringomas with predominant acral distribution.⁸ Compared to classic syringomas, the acral variant is associated with an older age of onset as well as a similar prevalence between men and women.⁹ Acral eruptive syringoma (AES) usually is isolated to the distal arms and legs. The most commonly affected region is the anterior surface of the forearms, although involvement of the dorsal hands, wrists, and feet also has been reported.^10-16

The first known case of AES, which was reported in 1977, described eruptive syringomas on the dorsal hands of a healthy 31-year-old man.¹⁷ Several cases have been reported since then, mostly in patients aged 30 to 60 years, with predominant involvement of the dorsal hands and forearms.^18-24 A review of Embase as well as PubMed articles indexed for MEDLINE using the search terms syringoma OR eccrine ductal tumor and eruptive OR acral OR arms OR forearms OR extremities identified 19 reported cases of AES between 1977 and 2023. For the reported AES cases, the mean (SD) age at diagnosis was 45.1 years (15.96 years), with patient ages ranging from 19 to 76 years. Notably, most cases occurred in individuals aged between 30 and 60 years, which deviates from the typical age of onset of localized syringomas, commonly seen during puberty or early adulthood.

Currently, AES is categorized within the clinical presentation of eruptive syringoma. Nevertheless, some authors have proposed classifying it as a distinct fifth clinical group due to specific features that distinguish it from generalized eruptive syringoma.⁹ This reclassification has considerable implications for the differential diagnosis, particularly because exclusive acral involvement poses a substantial diagnostic challenge and often requires histologic confirmation.

As shown in the Figure, histopathologic examination revealed tubular structures in the upper dermis with characteristic comma-shaped extensions. Some of these structures were lined with cuboidal cells and contained eosinophilic material within the lumen. There was no involvement of the epidermis or deeper dermis. The histologic features were consistent with syringoma, which is distinguished by its predominant involvement of the upper dermis and the presence of enlarged, dilated eccrine ducts, as observed in our case.

Treatment of syringomas often is challenging due to the high rate of recurrence and the risk for postinflammatory hyperpigmentation. Since the condition is benign, treatment typically is pursued for aesthetic reasons. Various therapeutic approaches have been reported, each with diverse response rates. The most common method involves surgical intervention, either with electrodesiccation or CO₂ laser—both of which have shown satisfactory resolution of lesions without recurrence at 1-year follow-up, with no major scarring reported.^25,26 Alternatively, topical management with retinoids daily over a 4-month period leads to flattening of the tumors with no further appearance of new lesions.²⁷ Despite the availability of numerous management options, establishing a first-line treatment remains controversial due to the high risk for recurrence and the variability in the number and location of lesions among individual patients. In our case, given the benign nature of syringomas, the asymptomatic nature of the lesions, the involvement of noncritical aesthetic areas, and the limited response to noninvasive therapeutic options, the patient was informed of the diagnosis, and no further pharmacologic or surgical intervention was pursued.

THE DIAGNOSIS: Syphilis

The differential diagnosis of oral lesions can be complex; in our patient, we considered conditions such as pyogenic granuloma, herpes simplex virus, and syphilis, despite the presence of pain. Immunohistochemical staining for spirochete antigens was positive, and serologic confirmation through a positive rapid plasma reagin (RPR) test confirmed the diagnosis of primary syphilis. The patient was promptly referred back to the primary care physician for treatment with intramuscular penicillin, leading to resolution of the lesion. At 3 months’ follow-up in our clinic, the lesion was fully resolved.

A primary syphilitic chancre is the initial lesion caused by Treponema pallidum, typically manifesting as a painless ulcer at the infection site, usually in the genital area; however, chancres also may manifest in other locations (eg, the anus or oral cavity) due to direct contact with infectious lesions on another individual. Our case represents an atypical presentation of an oral syphilitic chancre.

Syphilis is a sexually transmitted infection with various clinical manifestations. It is crucial to consider syphilis in the differential diagnosis of ulcerative lesions even when pain is present, especially in high-risk individuals such as those who engage in unprotected sex.^1,2 Oral syphilitic chancres have been documented in the medical literature for more than a century, underscoring the importance of maintaining a high index of suspicion for diagnosis and a low threshold for obtaining an RPR test to facilitate early detection and treatment.^2,3 Notably, the prevalence of syphilis is higher in men who have sex with men, particularly among those who engage in unprotected oral and anal sex. Increased screening and early treatment are essential to control the spread of disease within all populations. Doxycycline postexposure prophylaxis (doxyPEP) is used as a preventive measure for syphilis, chlamydia, and gonorrhea.⁴ This regimen consists of 200 mg of doxycycline taken within 24 hours but no later than 72 hours after unprotected anal, vaginal, or oral sex.

Our case highlights the importance of considering the differential diagnosis of oral ulcers, particularly in high-risk populations such as men who have sex with men. Prompt diagnosis, effective treatment, and preventive strategies such as doxyPEP are essential for controlling syphilis. Comprehensive patient education and regular follow-up appointments are critical components of successful management.

The United States has experienced a considerable rise in primary and congenital syphilis cases, with an 80% increase between 2018 and 2022.⁶ Serologic testing is the primary method for diagnosing, staging, and managing syphilis. Sexually active patients with suspected syphilis or unexplained symptoms should undergo testing. Prompt diagnosis and treatment can prevent systemic complications, including ocular involvement and permanent blindness.

Syphilis is transmitted through direct contact with a syphilitic ulcer or saliva or blood from an infected individual. Oral syphilitic ulcers can develop on the lips, tongue, oral mucosa, and tonsils. Chancres can range from a few millimeters to several centimeters, with an incubation period of 10 to 90 days (average, 21 days). The chancre lasts 3 to 6 weeks and heals spontaneously. Without treatment, primary syphilis can progress to secondary syphilis, characterized by a papulosquamous eruption and mucosal involvement, and potentially tertiary syphilis, which can affect the central nervous system, heart, bones, and skin.⁷

Immunocompromised patients, especially those diagnosed with HIV, face increased risks including altered clinical presentations (eg, multiple or deep chancres), delayed healing, overlapping stages of disease, and increased severity of organ involvement. All sexually active individuals should be screened for syphilis every 3 to 6 months, particularly those with unexplained oral ulcers.

Serologic testing is fundamental for syphilis diagnosis and management. Nontreponemal tests such as RPR and treponemal tests such as the fluorescent treponemal antibody absorption test provide comprehensive diagnostic information. Early diagnosis and empiric treatment are crucial in suspected cases. Ocular screening is recommended for suspected or confirmed syphilis cases.⁷

Management of syphilis includes treating all sexual partners and providing thorough patient education on the disease. Monitoring for the Jarisch-Herxheimer reaction—an acute febrile reaction following penicillin therapy—is important, especially in pregnant patients.5 Serologic evaluation at 6 and 12 months posttreatment is recommended, with more frequent evaluations if follow-up is uncertain, particularly for those with inconsistent access to health care or in whom reinfection is suspected. Guidelines from the Centers for Disease Control and Prevention advocate for intramuscular penicillin G benzathine as the preferred treatment, with specific dosing for adults and children.⁷ Due to the ongoing bicillin shortage, alternatives such as extencilline have temporarily been allowed for use in the United States.⁸

The rising incidence of syphilis in the United States underscores the critical need for enhanced public health initiatives focusing on education, screening, and early intervention. Comprehensive sexual education that includes information about syphilis and other sexually transmitted infections, proper use of prophylactic measures such as condoms, and the benefits of doxyPEP can considerably reduce transmission rates. Health care providers should routinely discuss these preventive measures with their patients, especially those in high-risk groups.

Our case highlights the importance of considering syphilis in the differential diagnosis of oral ulcers, particularly in high-risk populations. Timely diagnosis, effective treatment, and preventive measures such as doxyPEP are essential for managing and controlling syphilis. The rising incidence of syphilis in the United States warrants increased screening, patient education, and public health interventions to address this notable health challenge. The syphilis crisis calls for coordinated efforts from health care providers, public health officials, and community leaders to curb the spread of this infection and protect public health.

THE DIAGNOSIS: Syphilis

The differential diagnosis of oral lesions can be complex; in our patient, we considered conditions such as pyogenic granuloma, herpes simplex virus, and syphilis, despite the presence of pain. Immunohistochemical staining for spirochete antigens was positive, and serologic confirmation through a positive rapid plasma reagin (RPR) test confirmed the diagnosis of primary syphilis. The patient was promptly referred back to the primary care physician for treatment with intramuscular penicillin, leading to resolution of the lesion. At 3 months’ follow-up in our clinic, the lesion was fully resolved.

A primary syphilitic chancre is the initial lesion caused by Treponema pallidum, typically manifesting as a painless ulcer at the infection site, usually in the genital area; however, chancres also may manifest in other locations (eg, the anus or oral cavity) due to direct contact with infectious lesions on another individual. Our case represents an atypical presentation of an oral syphilitic chancre.

Syphilis is a sexually transmitted infection with various clinical manifestations. It is crucial to consider syphilis in the differential diagnosis of ulcerative lesions even when pain is present, especially in high-risk individuals such as those who engage in unprotected sex.^1,2 Oral syphilitic chancres have been documented in the medical literature for more than a century, underscoring the importance of maintaining a high index of suspicion for diagnosis and a low threshold for obtaining an RPR test to facilitate early detection and treatment.^2,3 Notably, the prevalence of syphilis is higher in men who have sex with men, particularly among those who engage in unprotected oral and anal sex. Increased screening and early treatment are essential to control the spread of disease within all populations. Doxycycline postexposure prophylaxis (doxyPEP) is used as a preventive measure for syphilis, chlamydia, and gonorrhea.⁴ This regimen consists of 200 mg of doxycycline taken within 24 hours but no later than 72 hours after unprotected anal, vaginal, or oral sex.

Our case highlights the importance of considering the differential diagnosis of oral ulcers, particularly in high-risk populations such as men who have sex with men. Prompt diagnosis, effective treatment, and preventive strategies such as doxyPEP are essential for controlling syphilis. Comprehensive patient education and regular follow-up appointments are critical components of successful management.

The United States has experienced a considerable rise in primary and congenital syphilis cases, with an 80% increase between 2018 and 2022.⁶ Serologic testing is the primary method for diagnosing, staging, and managing syphilis. Sexually active patients with suspected syphilis or unexplained symptoms should undergo testing. Prompt diagnosis and treatment can prevent systemic complications, including ocular involvement and permanent blindness.

Syphilis is transmitted through direct contact with a syphilitic ulcer or saliva or blood from an infected individual. Oral syphilitic ulcers can develop on the lips, tongue, oral mucosa, and tonsils. Chancres can range from a few millimeters to several centimeters, with an incubation period of 10 to 90 days (average, 21 days). The chancre lasts 3 to 6 weeks and heals spontaneously. Without treatment, primary syphilis can progress to secondary syphilis, characterized by a papulosquamous eruption and mucosal involvement, and potentially tertiary syphilis, which can affect the central nervous system, heart, bones, and skin.⁷

Immunocompromised patients, especially those diagnosed with HIV, face increased risks including altered clinical presentations (eg, multiple or deep chancres), delayed healing, overlapping stages of disease, and increased severity of organ involvement. All sexually active individuals should be screened for syphilis every 3 to 6 months, particularly those with unexplained oral ulcers.

Serologic testing is fundamental for syphilis diagnosis and management. Nontreponemal tests such as RPR and treponemal tests such as the fluorescent treponemal antibody absorption test provide comprehensive diagnostic information. Early diagnosis and empiric treatment are crucial in suspected cases. Ocular screening is recommended for suspected or confirmed syphilis cases.⁷

Management of syphilis includes treating all sexual partners and providing thorough patient education on the disease. Monitoring for the Jarisch-Herxheimer reaction—an acute febrile reaction following penicillin therapy—is important, especially in pregnant patients.5 Serologic evaluation at 6 and 12 months posttreatment is recommended, with more frequent evaluations if follow-up is uncertain, particularly for those with inconsistent access to health care or in whom reinfection is suspected. Guidelines from the Centers for Disease Control and Prevention advocate for intramuscular penicillin G benzathine as the preferred treatment, with specific dosing for adults and children.⁷ Due to the ongoing bicillin shortage, alternatives such as extencilline have temporarily been allowed for use in the United States.⁸

The rising incidence of syphilis in the United States underscores the critical need for enhanced public health initiatives focusing on education, screening, and early intervention. Comprehensive sexual education that includes information about syphilis and other sexually transmitted infections, proper use of prophylactic measures such as condoms, and the benefits of doxyPEP can considerably reduce transmission rates. Health care providers should routinely discuss these preventive measures with their patients, especially those in high-risk groups.

Our case highlights the importance of considering syphilis in the differential diagnosis of oral ulcers, particularly in high-risk populations. Timely diagnosis, effective treatment, and preventive measures such as doxyPEP are essential for managing and controlling syphilis. The rising incidence of syphilis in the United States warrants increased screening, patient education, and public health interventions to address this notable health challenge. The syphilis crisis calls for coordinated efforts from health care providers, public health officials, and community leaders to curb the spread of this infection and protect public health.

THE DIAGNOSIS: Syphilis

The differential diagnosis of oral lesions can be complex; in our patient, we considered conditions such as pyogenic granuloma, herpes simplex virus, and syphilis, despite the presence of pain. Immunohistochemical staining for spirochete antigens was positive, and serologic confirmation through a positive rapid plasma reagin (RPR) test confirmed the diagnosis of primary syphilis. The patient was promptly referred back to the primary care physician for treatment with intramuscular penicillin, leading to resolution of the lesion. At 3 months’ follow-up in our clinic, the lesion was fully resolved.

A primary syphilitic chancre is the initial lesion caused by Treponema pallidum, typically manifesting as a painless ulcer at the infection site, usually in the genital area; however, chancres also may manifest in other locations (eg, the anus or oral cavity) due to direct contact with infectious lesions on another individual. Our case represents an atypical presentation of an oral syphilitic chancre.

Syphilis is a sexually transmitted infection with various clinical manifestations. It is crucial to consider syphilis in the differential diagnosis of ulcerative lesions even when pain is present, especially in high-risk individuals such as those who engage in unprotected sex.^1,2 Oral syphilitic chancres have been documented in the medical literature for more than a century, underscoring the importance of maintaining a high index of suspicion for diagnosis and a low threshold for obtaining an RPR test to facilitate early detection and treatment.^2,3 Notably, the prevalence of syphilis is higher in men who have sex with men, particularly among those who engage in unprotected oral and anal sex. Increased screening and early treatment are essential to control the spread of disease within all populations. Doxycycline postexposure prophylaxis (doxyPEP) is used as a preventive measure for syphilis, chlamydia, and gonorrhea.⁴ This regimen consists of 200 mg of doxycycline taken within 24 hours but no later than 72 hours after unprotected anal, vaginal, or oral sex.

Our case highlights the importance of considering the differential diagnosis of oral ulcers, particularly in high-risk populations such as men who have sex with men. Prompt diagnosis, effective treatment, and preventive strategies such as doxyPEP are essential for controlling syphilis. Comprehensive patient education and regular follow-up appointments are critical components of successful management.

The United States has experienced a considerable rise in primary and congenital syphilis cases, with an 80% increase between 2018 and 2022.⁶ Serologic testing is the primary method for diagnosing, staging, and managing syphilis. Sexually active patients with suspected syphilis or unexplained symptoms should undergo testing. Prompt diagnosis and treatment can prevent systemic complications, including ocular involvement and permanent blindness.

Syphilis is transmitted through direct contact with a syphilitic ulcer or saliva or blood from an infected individual. Oral syphilitic ulcers can develop on the lips, tongue, oral mucosa, and tonsils. Chancres can range from a few millimeters to several centimeters, with an incubation period of 10 to 90 days (average, 21 days). The chancre lasts 3 to 6 weeks and heals spontaneously. Without treatment, primary syphilis can progress to secondary syphilis, characterized by a papulosquamous eruption and mucosal involvement, and potentially tertiary syphilis, which can affect the central nervous system, heart, bones, and skin.⁷

Immunocompromised patients, especially those diagnosed with HIV, face increased risks including altered clinical presentations (eg, multiple or deep chancres), delayed healing, overlapping stages of disease, and increased severity of organ involvement. All sexually active individuals should be screened for syphilis every 3 to 6 months, particularly those with unexplained oral ulcers.

Serologic testing is fundamental for syphilis diagnosis and management. Nontreponemal tests such as RPR and treponemal tests such as the fluorescent treponemal antibody absorption test provide comprehensive diagnostic information. Early diagnosis and empiric treatment are crucial in suspected cases. Ocular screening is recommended for suspected or confirmed syphilis cases.⁷

Management of syphilis includes treating all sexual partners and providing thorough patient education on the disease. Monitoring for the Jarisch-Herxheimer reaction—an acute febrile reaction following penicillin therapy—is important, especially in pregnant patients.5 Serologic evaluation at 6 and 12 months posttreatment is recommended, with more frequent evaluations if follow-up is uncertain, particularly for those with inconsistent access to health care or in whom reinfection is suspected. Guidelines from the Centers for Disease Control and Prevention advocate for intramuscular penicillin G benzathine as the preferred treatment, with specific dosing for adults and children.⁷ Due to the ongoing bicillin shortage, alternatives such as extencilline have temporarily been allowed for use in the United States.⁸

The rising incidence of syphilis in the United States underscores the critical need for enhanced public health initiatives focusing on education, screening, and early intervention. Comprehensive sexual education that includes information about syphilis and other sexually transmitted infections, proper use of prophylactic measures such as condoms, and the benefits of doxyPEP can considerably reduce transmission rates. Health care providers should routinely discuss these preventive measures with their patients, especially those in high-risk groups.

Our case highlights the importance of considering syphilis in the differential diagnosis of oral ulcers, particularly in high-risk populations. Timely diagnosis, effective treatment, and preventive measures such as doxyPEP are essential for managing and controlling syphilis. The rising incidence of syphilis in the United States warrants increased screening, patient education, and public health interventions to address this notable health challenge. The syphilis crisis calls for coordinated efforts from health care providers, public health officials, and community leaders to curb the spread of this infection and protect public health.

THE DIAGNOSIS: Bullous Hemorrhagic Dermatosis

Biopsy results showed an intraepidermal blister with a floor composed of maturing epidermis. The roof of the blister was composed of necrotic keratinocytes with overlying orthokeratosis, and the cavity was filled with a moderate amount of fibrin and dead cells with neutrophils. Direct immunofluorescence (DIF) using specific antihuman IgG, IgM, IgA, C3, and fibrin was negative. Aerobic, anaerobic, and fungal cultures also were negative. With these histopathologic findings, medication exposure, and timing of bullae onset, our patient was diagnosed with bullous hemorrhagic dermatosis (BHD) secondary to enoxaparin administration. Enoxaparin was continued due to increased risk for coagulopathy, and there was complete resolution of the bullae after 5 weeks with no residual symptoms.

Bullous hemorrhagic dermatosis is a rare eruption that can occur after administration of heparin and low-molecular-weight heparin, with enoxaparin being the most commonly implicated drug.¹ The lesions typically are seen in elderly men in the seventh decade of life and appear within a median of 7 days after drug exposure. The time course for the postexposure eruption can vary from 2 to 21 days, with reports of skin lesions appearing up to 4 months after exposure.^1,2 hemorrhagic bullae (Figure) typically on the arms and legs, though lesions also can develop on the trunk. The lesions can occur in distant areas from the injection site, suggesting BHD may be a systemic reaction, although the etiology is poorly understood.¹

Another heparin reaction that can manifest similarly to BHD is heparin-induced skin necrosis.³ Patients with this condition also may have associated heparin-induced thrombocytopenia upon laboratory investigation and have a more aggressive clinical course than BHD. Biopsy can help differentiate BHD and early heparin-induced skin necrosis if the clinical manifestation is unclear. Histopathologically, BHD typically has intraepidermal bullae filled with blood, whereas heparin-induced skin necrosis has dermal thrombi.^1,4 Treatment of both conditions differs in whether to discontinue anticoagulants: heparin-induced skin necrosis requires discontinuation of the medication, while BHD does not.^2,3

In patients with BHD, the lesions are self-resolving, and treatment is supportive, although whether enoxaparin is discontinued varies among physicians.² Lesions typically resolve within 2 weeks of onset, although it is unclear whether continuing anticoagulants delays resolution.¹ Discontinuing anticoagulants in certain patients can be life-threatening due to complex comorbidities (eg, risk for venous thromboembolism or pulmonary embolism from prolonged hospitalization or severe trauma) and is not necessary for the resolution of BHD.

In addition to BHD and heparin-induced skin necrosis, our differential diagnosis included bullous pemphigoid, coma blisters, and Vibrio vulnificus infection. Although bullous pemphigoid can manifest with tense bullae that are pauci-inflammatory on histology, DIF would show linear IgG and C3 deposition at the dermal-epidermal junction. In our patient, DIF was negative and favored another etiology for the lesions. Coma blisters can occur in areas of sustained pressure and typically develop in patients with a prolonged hospitalization or those who are sedentary for long periods of time. The distribution of bullae on our patient’s bilateral pretibial shins made this diagnosis unlikely. Vibrio vulnificus infection can manifest as hemorrhagic bullae, though typically after a break in the skin exposed to brackish water. Vibrio vulnificus infection can be life-threatening, resulting in septicemia and increased mortality, and a thorough patient history is important for diagnosis.⁵

THE DIAGNOSIS: Bullous Hemorrhagic Dermatosis

Biopsy results showed an intraepidermal blister with a floor composed of maturing epidermis. The roof of the blister was composed of necrotic keratinocytes with overlying orthokeratosis, and the cavity was filled with a moderate amount of fibrin and dead cells with neutrophils. Direct immunofluorescence (DIF) using specific antihuman IgG, IgM, IgA, C3, and fibrin was negative. Aerobic, anaerobic, and fungal cultures also were negative. With these histopathologic findings, medication exposure, and timing of bullae onset, our patient was diagnosed with bullous hemorrhagic dermatosis (BHD) secondary to enoxaparin administration. Enoxaparin was continued due to increased risk for coagulopathy, and there was complete resolution of the bullae after 5 weeks with no residual symptoms.

Bullous hemorrhagic dermatosis is a rare eruption that can occur after administration of heparin and low-molecular-weight heparin, with enoxaparin being the most commonly implicated drug.¹ The lesions typically are seen in elderly men in the seventh decade of life and appear within a median of 7 days after drug exposure. The time course for the postexposure eruption can vary from 2 to 21 days, with reports of skin lesions appearing up to 4 months after exposure.^1,2 hemorrhagic bullae (Figure) typically on the arms and legs, though lesions also can develop on the trunk. The lesions can occur in distant areas from the injection site, suggesting BHD may be a systemic reaction, although the etiology is poorly understood.¹

Another heparin reaction that can manifest similarly to BHD is heparin-induced skin necrosis.³ Patients with this condition also may have associated heparin-induced thrombocytopenia upon laboratory investigation and have a more aggressive clinical course than BHD. Biopsy can help differentiate BHD and early heparin-induced skin necrosis if the clinical manifestation is unclear. Histopathologically, BHD typically has intraepidermal bullae filled with blood, whereas heparin-induced skin necrosis has dermal thrombi.^1,4 Treatment of both conditions differs in whether to discontinue anticoagulants: heparin-induced skin necrosis requires discontinuation of the medication, while BHD does not.^2,3

In patients with BHD, the lesions are self-resolving, and treatment is supportive, although whether enoxaparin is discontinued varies among physicians.² Lesions typically resolve within 2 weeks of onset, although it is unclear whether continuing anticoagulants delays resolution.¹ Discontinuing anticoagulants in certain patients can be life-threatening due to complex comorbidities (eg, risk for venous thromboembolism or pulmonary embolism from prolonged hospitalization or severe trauma) and is not necessary for the resolution of BHD.

In addition to BHD and heparin-induced skin necrosis, our differential diagnosis included bullous pemphigoid, coma blisters, and Vibrio vulnificus infection. Although bullous pemphigoid can manifest with tense bullae that are pauci-inflammatory on histology, DIF would show linear IgG and C3 deposition at the dermal-epidermal junction. In our patient, DIF was negative and favored another etiology for the lesions. Coma blisters can occur in areas of sustained pressure and typically develop in patients with a prolonged hospitalization or those who are sedentary for long periods of time. The distribution of bullae on our patient’s bilateral pretibial shins made this diagnosis unlikely. Vibrio vulnificus infection can manifest as hemorrhagic bullae, though typically after a break in the skin exposed to brackish water. Vibrio vulnificus infection can be life-threatening, resulting in septicemia and increased mortality, and a thorough patient history is important for diagnosis.⁵

THE DIAGNOSIS: Bullous Hemorrhagic Dermatosis

Biopsy results showed an intraepidermal blister with a floor composed of maturing epidermis. The roof of the blister was composed of necrotic keratinocytes with overlying orthokeratosis, and the cavity was filled with a moderate amount of fibrin and dead cells with neutrophils. Direct immunofluorescence (DIF) using specific antihuman IgG, IgM, IgA, C3, and fibrin was negative. Aerobic, anaerobic, and fungal cultures also were negative. With these histopathologic findings, medication exposure, and timing of bullae onset, our patient was diagnosed with bullous hemorrhagic dermatosis (BHD) secondary to enoxaparin administration. Enoxaparin was continued due to increased risk for coagulopathy, and there was complete resolution of the bullae after 5 weeks with no residual symptoms.

Bullous hemorrhagic dermatosis is a rare eruption that can occur after administration of heparin and low-molecular-weight heparin, with enoxaparin being the most commonly implicated drug.¹ The lesions typically are seen in elderly men in the seventh decade of life and appear within a median of 7 days after drug exposure. The time course for the postexposure eruption can vary from 2 to 21 days, with reports of skin lesions appearing up to 4 months after exposure.^1,2 hemorrhagic bullae (Figure) typically on the arms and legs, though lesions also can develop on the trunk. The lesions can occur in distant areas from the injection site, suggesting BHD may be a systemic reaction, although the etiology is poorly understood.¹

Another heparin reaction that can manifest similarly to BHD is heparin-induced skin necrosis.³ Patients with this condition also may have associated heparin-induced thrombocytopenia upon laboratory investigation and have a more aggressive clinical course than BHD. Biopsy can help differentiate BHD and early heparin-induced skin necrosis if the clinical manifestation is unclear. Histopathologically, BHD typically has intraepidermal bullae filled with blood, whereas heparin-induced skin necrosis has dermal thrombi.^1,4 Treatment of both conditions differs in whether to discontinue anticoagulants: heparin-induced skin necrosis requires discontinuation of the medication, while BHD does not.^2,3

In patients with BHD, the lesions are self-resolving, and treatment is supportive, although whether enoxaparin is discontinued varies among physicians.² Lesions typically resolve within 2 weeks of onset, although it is unclear whether continuing anticoagulants delays resolution.¹ Discontinuing anticoagulants in certain patients can be life-threatening due to complex comorbidities (eg, risk for venous thromboembolism or pulmonary embolism from prolonged hospitalization or severe trauma) and is not necessary for the resolution of BHD.

In addition to BHD and heparin-induced skin necrosis, our differential diagnosis included bullous pemphigoid, coma blisters, and Vibrio vulnificus infection. Although bullous pemphigoid can manifest with tense bullae that are pauci-inflammatory on histology, DIF would show linear IgG and C3 deposition at the dermal-epidermal junction. In our patient, DIF was negative and favored another etiology for the lesions. Coma blisters can occur in areas of sustained pressure and typically develop in patients with a prolonged hospitalization or those who are sedentary for long periods of time. The distribution of bullae on our patient’s bilateral pretibial shins made this diagnosis unlikely. Vibrio vulnificus infection can manifest as hemorrhagic bullae, though typically after a break in the skin exposed to brackish water. Vibrio vulnificus infection can be life-threatening, resulting in septicemia and increased mortality, and a thorough patient history is important for diagnosis.⁵

THE DIAGNOSIS: Apocrine Hidrocystoma

Histology for all 3 lesions demonstrated similar cystic structures lined by a dual layer of epithelial cells, with the outermost layer composed of flattened myoepithelial cells and the inner layer composed of cells with apocrine features (Figure 1). Based on these findings, a diagnosis of apocrine hidrocystoma was made. The patient underwent successful surgical excision shortly thereafter without recurrence at follow-up 1 year later. 

Apocrine hidrocystomas are rare benign cystic lesions that are considered to be adenomatous proliferations of apocrine glands. They typically manifest as solitary asymptomatic lesions measuring 3 to 15 mm.¹ They tend to appear on the face, usually in the periorbital region, but also have been described on the neck, scalp, trunk, arms, and legs.^2-4 Multiple apocrine hidrocystomas can be a marker of 2 rare inherited disorders: Gorlin-Goltz syndrome and Schopf-Schulz-Passarge syndrome.⁵ Apocrine hidrocystomas may be flesh colored or may have a blue, black, or brown appearance due to the Tyndall effect, in which light with shorter wavelengths is scattered by the contents of the lesions.² Histologically, apocrine hidrocystomas are cysts lined by a dual layer of epithelial cells. The inner layer is composed of cells with apocrine features, and the outer layer is composed of flattened myoepithelial cells. Due to their range of colors and predilection for sun-exposed surfaces, apocrine hidrocystomas may be mistaken for various malignant neoplasms, including melanoma.^6,7

The differential diagnosis for our patient included agminated blue nevi, melanoma, pigmented basal cell carcinoma (BCC), and seborrheic keratosis. A blue nevus is a dermal melanocytic lesion that manifests as a well-demarcated, blue to blue-black papule that typically appears on the face, scalp, arms, legs, lower back, and buttocks. Although there are several histologic subtypes, the common blue nevus usually manifests as a solitary lesion measuring less than 1 cm, often developing during childhood to young adulthood.⁸ Histologically, common blue nevi are characterized by a dermal proliferation of deeply pigmented bipolar spindled melanocytes embedded in thickened collagen bundles, often with scattered epithelioid melanophages, and no conspicuous mitotic activity (Figure 2).⁹ There are other types of blue nevi, including cellular blue nevi, which tend to be larger and manifest commonly on the buttocks and sacrococcygeal region in early adulthood.⁹ Histologically, cellular blue nevi contain oval to spindled melanocytes with scattered melanophages forming a well-demarcated nodule typically in the reticular dermis. There may be bulbous extension into the subcutaneous adipose tissue. Occasional mitoses may be seen.^9,10 Melanoma can arise from common or cellular blue nevi, though it more frequently occurs with cellular blue nevi. Other subtypes of blue nevi have been described, including the sclerosing, plaque-type, combined, hypomelanotic/amelanotic, and pigmented epithelioid melanocytoma.¹¹ However, they typically have features of the common blue nevus or cellular blue nevus, such as oval/spindle cell morphology, some degree of melanin, and biphasic architecture, but are classified according to their dominant histologic characteristics. 

Given the location of our patient’s lesions on the scalp and his extensive history of sun exposure, malignancy was high in the differential. Multiple synchronous primary melanomas including nodular melanoma, blue nevus–like metastatic melanoma, and metastatic melanoma were considered. The leg and the scalp have the highest reported incidence of cutaneous metastases of melanoma, with many cases presenting as dermal or subcutaneous nodules and eruptive blue nevus–like papules, similar to our patient’s clinical presentation.^12,13 Nodular melanoma (NM) is one of 4 major types of melanoma, accounting for approximately 15% to 30% of cases in the United States.¹⁴ Nodular melanoma typically manifests as a smooth, raised, symmetric, well-circumscribed lesion with variable pigmentation, from very dark to amelanotic. Histologically, NM is defined as a dermal mass, either in isolation or with an epidermal component, not to exceed 3 rete ridges beyond the dermal component.¹⁵ Tumor cells have a high cell density with pleomorphism, usually with atypical epithelioid cells with vesicular nuclei and irregular cytoplasm, and occasionally spindle cells (Figure 2).¹⁶ Mitoses and necrosis are frequent. Scalp location independently is responsible for worse survival, both overall and melanoma specific.¹⁷ Nodular melanoma tends to have greater Breslow thickness at diagnosis than other melanoma subtypes and often carries a worse prognosis. 

Malignant melanomas that develop from or in conjunction with or bear histologic resemblance to blue nevi are termed blue nevus–like melanoma or blue nevus–associated melanoma. These malignancies are exceedingly rare, accounting for only 0.3% of melanomas in one Turkey-based multicenter study.¹⁸ The histologic criteria for diagnosing blue nevus–like melanoma are poorly defined, and terminology of these lesions has led to some debate in naming conventions.¹⁹ Nevertheless, unlike blue nevus, blue nevus–like melanoma demonstrates histologic features of malignancy, including pleomorphism, prominent nucleoli, mitotic activity, vascular invasion, and potential necrosis.¹⁰ The lack of an inflammatory infiltrate, surrounding fibrosis, junctional activity, and pre-existing nevus can help distinguish cutaneous melanoma metastases from primary nodular melanoma. Immunohistochemical stains such as S100, Melan-A/MART1, or SOX-10 can help confirm melanocytic lineage.¹² 

Pigmented BCC is a clinical and histologic variant of BCC characterized by increased melanin pigmentation due to melanocytes admixed with tumor cells. Dermoscopically, the pigment can have a maple leaf–like appearance with spoke-wheel areas, in-focus dots, and concentric structures at the dermoepidermal junction, which is more characteristic of superficial and infiltrating BCC.²⁰ In nodular BCC, the pigment occurs as blue-gray ovoid nests and globules in deeper layers of the dermis.²⁰ 

Seborrheic keratoses (SKs) can vary widely in clinical appearance, with pigmentation ranging from flesh colored to yellow to brown to black. Melanoacanthomas are acanthotic SKs that are highly pigmented due to intermixed epidermal melanocytes and subepidermal melanophages.²¹ Dermoscopy can help distinguish cutaneous malignancies from SKs, which often demonstrate fissures and ridges, comedolike openings, and milialike cysts. Biopsy sometimes is required to assess for malignancy, as was the case in our patient. The classic histologic features of SKs include acanthosis, papillomatosis, and hyperkeratosis.²² 

This case highlights the need to consider apocrine hidrocystoma, along with malignancy, in the differential diagnosis of pigmented cystic masses of the face and scalp. Because apocrine hidrocystomas are benign, they do not need to be treated but often are surgically excised for cosmesis or complete histopathologic examination. Destruction via electrodessication, carbon dioxide ablation, trichloroacetic acid chemical ablation, botulinum toxin injection, and anticholinergic creams sometimes is used, especially for cosmetic treatment of multiple small lesions.⁵ Our patient was treated with surgical excision with no evidence of recurrence on follow-up 1 year later. 

THE DIAGNOSIS: Apocrine Hidrocystoma

Histology for all 3 lesions demonstrated similar cystic structures lined by a dual layer of epithelial cells, with the outermost layer composed of flattened myoepithelial cells and the inner layer composed of cells with apocrine features (Figure 1). Based on these findings, a diagnosis of apocrine hidrocystoma was made. The patient underwent successful surgical excision shortly thereafter without recurrence at follow-up 1 year later. 

Apocrine hidrocystomas are rare benign cystic lesions that are considered to be adenomatous proliferations of apocrine glands. They typically manifest as solitary asymptomatic lesions measuring 3 to 15 mm.¹ They tend to appear on the face, usually in the periorbital region, but also have been described on the neck, scalp, trunk, arms, and legs.^2-4 Multiple apocrine hidrocystomas can be a marker of 2 rare inherited disorders: Gorlin-Goltz syndrome and Schopf-Schulz-Passarge syndrome.⁵ Apocrine hidrocystomas may be flesh colored or may have a blue, black, or brown appearance due to the Tyndall effect, in which light with shorter wavelengths is scattered by the contents of the lesions.² Histologically, apocrine hidrocystomas are cysts lined by a dual layer of epithelial cells. The inner layer is composed of cells with apocrine features, and the outer layer is composed of flattened myoepithelial cells. Due to their range of colors and predilection for sun-exposed surfaces, apocrine hidrocystomas may be mistaken for various malignant neoplasms, including melanoma.^6,7

The differential diagnosis for our patient included agminated blue nevi, melanoma, pigmented basal cell carcinoma (BCC), and seborrheic keratosis. A blue nevus is a dermal melanocytic lesion that manifests as a well-demarcated, blue to blue-black papule that typically appears on the face, scalp, arms, legs, lower back, and buttocks. Although there are several histologic subtypes, the common blue nevus usually manifests as a solitary lesion measuring less than 1 cm, often developing during childhood to young adulthood.⁸ Histologically, common blue nevi are characterized by a dermal proliferation of deeply pigmented bipolar spindled melanocytes embedded in thickened collagen bundles, often with scattered epithelioid melanophages, and no conspicuous mitotic activity (Figure 2).⁹ There are other types of blue nevi, including cellular blue nevi, which tend to be larger and manifest commonly on the buttocks and sacrococcygeal region in early adulthood.⁹ Histologically, cellular blue nevi contain oval to spindled melanocytes with scattered melanophages forming a well-demarcated nodule typically in the reticular dermis. There may be bulbous extension into the subcutaneous adipose tissue. Occasional mitoses may be seen.^9,10 Melanoma can arise from common or cellular blue nevi, though it more frequently occurs with cellular blue nevi. Other subtypes of blue nevi have been described, including the sclerosing, plaque-type, combined, hypomelanotic/amelanotic, and pigmented epithelioid melanocytoma.¹¹ However, they typically have features of the common blue nevus or cellular blue nevus, such as oval/spindle cell morphology, some degree of melanin, and biphasic architecture, but are classified according to their dominant histologic characteristics. 

Given the location of our patient’s lesions on the scalp and his extensive history of sun exposure, malignancy was high in the differential. Multiple synchronous primary melanomas including nodular melanoma, blue nevus–like metastatic melanoma, and metastatic melanoma were considered. The leg and the scalp have the highest reported incidence of cutaneous metastases of melanoma, with many cases presenting as dermal or subcutaneous nodules and eruptive blue nevus–like papules, similar to our patient’s clinical presentation.^12,13 Nodular melanoma (NM) is one of 4 major types of melanoma, accounting for approximately 15% to 30% of cases in the United States.¹⁴ Nodular melanoma typically manifests as a smooth, raised, symmetric, well-circumscribed lesion with variable pigmentation, from very dark to amelanotic. Histologically, NM is defined as a dermal mass, either in isolation or with an epidermal component, not to exceed 3 rete ridges beyond the dermal component.¹⁵ Tumor cells have a high cell density with pleomorphism, usually with atypical epithelioid cells with vesicular nuclei and irregular cytoplasm, and occasionally spindle cells (Figure 2).¹⁶ Mitoses and necrosis are frequent. Scalp location independently is responsible for worse survival, both overall and melanoma specific.¹⁷ Nodular melanoma tends to have greater Breslow thickness at diagnosis than other melanoma subtypes and often carries a worse prognosis. 

Malignant melanomas that develop from or in conjunction with or bear histologic resemblance to blue nevi are termed blue nevus–like melanoma or blue nevus–associated melanoma. These malignancies are exceedingly rare, accounting for only 0.3% of melanomas in one Turkey-based multicenter study.¹⁸ The histologic criteria for diagnosing blue nevus–like melanoma are poorly defined, and terminology of these lesions has led to some debate in naming conventions.¹⁹ Nevertheless, unlike blue nevus, blue nevus–like melanoma demonstrates histologic features of malignancy, including pleomorphism, prominent nucleoli, mitotic activity, vascular invasion, and potential necrosis.¹⁰ The lack of an inflammatory infiltrate, surrounding fibrosis, junctional activity, and pre-existing nevus can help distinguish cutaneous melanoma metastases from primary nodular melanoma. Immunohistochemical stains such as S100, Melan-A/MART1, or SOX-10 can help confirm melanocytic lineage.¹² 

Pigmented BCC is a clinical and histologic variant of BCC characterized by increased melanin pigmentation due to melanocytes admixed with tumor cells. Dermoscopically, the pigment can have a maple leaf–like appearance with spoke-wheel areas, in-focus dots, and concentric structures at the dermoepidermal junction, which is more characteristic of superficial and infiltrating BCC.²⁰ In nodular BCC, the pigment occurs as blue-gray ovoid nests and globules in deeper layers of the dermis.²⁰ 

Seborrheic keratoses (SKs) can vary widely in clinical appearance, with pigmentation ranging from flesh colored to yellow to brown to black. Melanoacanthomas are acanthotic SKs that are highly pigmented due to intermixed epidermal melanocytes and subepidermal melanophages.²¹ Dermoscopy can help distinguish cutaneous malignancies from SKs, which often demonstrate fissures and ridges, comedolike openings, and milialike cysts. Biopsy sometimes is required to assess for malignancy, as was the case in our patient. The classic histologic features of SKs include acanthosis, papillomatosis, and hyperkeratosis.²² 

This case highlights the need to consider apocrine hidrocystoma, along with malignancy, in the differential diagnosis of pigmented cystic masses of the face and scalp. Because apocrine hidrocystomas are benign, they do not need to be treated but often are surgically excised for cosmesis or complete histopathologic examination. Destruction via electrodessication, carbon dioxide ablation, trichloroacetic acid chemical ablation, botulinum toxin injection, and anticholinergic creams sometimes is used, especially for cosmetic treatment of multiple small lesions.⁵ Our patient was treated with surgical excision with no evidence of recurrence on follow-up 1 year later. 

THE DIAGNOSIS: Apocrine Hidrocystoma

Histology for all 3 lesions demonstrated similar cystic structures lined by a dual layer of epithelial cells, with the outermost layer composed of flattened myoepithelial cells and the inner layer composed of cells with apocrine features (Figure 1). Based on these findings, a diagnosis of apocrine hidrocystoma was made. The patient underwent successful surgical excision shortly thereafter without recurrence at follow-up 1 year later. 

Apocrine hidrocystomas are rare benign cystic lesions that are considered to be adenomatous proliferations of apocrine glands. They typically manifest as solitary asymptomatic lesions measuring 3 to 15 mm.¹ They tend to appear on the face, usually in the periorbital region, but also have been described on the neck, scalp, trunk, arms, and legs.^2-4 Multiple apocrine hidrocystomas can be a marker of 2 rare inherited disorders: Gorlin-Goltz syndrome and Schopf-Schulz-Passarge syndrome.⁵ Apocrine hidrocystomas may be flesh colored or may have a blue, black, or brown appearance due to the Tyndall effect, in which light with shorter wavelengths is scattered by the contents of the lesions.² Histologically, apocrine hidrocystomas are cysts lined by a dual layer of epithelial cells. The inner layer is composed of cells with apocrine features, and the outer layer is composed of flattened myoepithelial cells. Due to their range of colors and predilection for sun-exposed surfaces, apocrine hidrocystomas may be mistaken for various malignant neoplasms, including melanoma.^6,7

The differential diagnosis for our patient included agminated blue nevi, melanoma, pigmented basal cell carcinoma (BCC), and seborrheic keratosis. A blue nevus is a dermal melanocytic lesion that manifests as a well-demarcated, blue to blue-black papule that typically appears on the face, scalp, arms, legs, lower back, and buttocks. Although there are several histologic subtypes, the common blue nevus usually manifests as a solitary lesion measuring less than 1 cm, often developing during childhood to young adulthood.⁸ Histologically, common blue nevi are characterized by a dermal proliferation of deeply pigmented bipolar spindled melanocytes embedded in thickened collagen bundles, often with scattered epithelioid melanophages, and no conspicuous mitotic activity (Figure 2).⁹ There are other types of blue nevi, including cellular blue nevi, which tend to be larger and manifest commonly on the buttocks and sacrococcygeal region in early adulthood.⁹ Histologically, cellular blue nevi contain oval to spindled melanocytes with scattered melanophages forming a well-demarcated nodule typically in the reticular dermis. There may be bulbous extension into the subcutaneous adipose tissue. Occasional mitoses may be seen.^9,10 Melanoma can arise from common or cellular blue nevi, though it more frequently occurs with cellular blue nevi. Other subtypes of blue nevi have been described, including the sclerosing, plaque-type, combined, hypomelanotic/amelanotic, and pigmented epithelioid melanocytoma.¹¹ However, they typically have features of the common blue nevus or cellular blue nevus, such as oval/spindle cell morphology, some degree of melanin, and biphasic architecture, but are classified according to their dominant histologic characteristics. 

Given the location of our patient’s lesions on the scalp and his extensive history of sun exposure, malignancy was high in the differential. Multiple synchronous primary melanomas including nodular melanoma, blue nevus–like metastatic melanoma, and metastatic melanoma were considered. The leg and the scalp have the highest reported incidence of cutaneous metastases of melanoma, with many cases presenting as dermal or subcutaneous nodules and eruptive blue nevus–like papules, similar to our patient’s clinical presentation.^12,13 Nodular melanoma (NM) is one of 4 major types of melanoma, accounting for approximately 15% to 30% of cases in the United States.¹⁴ Nodular melanoma typically manifests as a smooth, raised, symmetric, well-circumscribed lesion with variable pigmentation, from very dark to amelanotic. Histologically, NM is defined as a dermal mass, either in isolation or with an epidermal component, not to exceed 3 rete ridges beyond the dermal component.¹⁵ Tumor cells have a high cell density with pleomorphism, usually with atypical epithelioid cells with vesicular nuclei and irregular cytoplasm, and occasionally spindle cells (Figure 2).¹⁶ Mitoses and necrosis are frequent. Scalp location independently is responsible for worse survival, both overall and melanoma specific.¹⁷ Nodular melanoma tends to have greater Breslow thickness at diagnosis than other melanoma subtypes and often carries a worse prognosis. 

Malignant melanomas that develop from or in conjunction with or bear histologic resemblance to blue nevi are termed blue nevus–like melanoma or blue nevus–associated melanoma. These malignancies are exceedingly rare, accounting for only 0.3% of melanomas in one Turkey-based multicenter study.¹⁸ The histologic criteria for diagnosing blue nevus–like melanoma are poorly defined, and terminology of these lesions has led to some debate in naming conventions.¹⁹ Nevertheless, unlike blue nevus, blue nevus–like melanoma demonstrates histologic features of malignancy, including pleomorphism, prominent nucleoli, mitotic activity, vascular invasion, and potential necrosis.¹⁰ The lack of an inflammatory infiltrate, surrounding fibrosis, junctional activity, and pre-existing nevus can help distinguish cutaneous melanoma metastases from primary nodular melanoma. Immunohistochemical stains such as S100, Melan-A/MART1, or SOX-10 can help confirm melanocytic lineage.¹² 

Pigmented BCC is a clinical and histologic variant of BCC characterized by increased melanin pigmentation due to melanocytes admixed with tumor cells. Dermoscopically, the pigment can have a maple leaf–like appearance with spoke-wheel areas, in-focus dots, and concentric structures at the dermoepidermal junction, which is more characteristic of superficial and infiltrating BCC.²⁰ In nodular BCC, the pigment occurs as blue-gray ovoid nests and globules in deeper layers of the dermis.²⁰ 

Seborrheic keratoses (SKs) can vary widely in clinical appearance, with pigmentation ranging from flesh colored to yellow to brown to black. Melanoacanthomas are acanthotic SKs that are highly pigmented due to intermixed epidermal melanocytes and subepidermal melanophages.²¹ Dermoscopy can help distinguish cutaneous malignancies from SKs, which often demonstrate fissures and ridges, comedolike openings, and milialike cysts. Biopsy sometimes is required to assess for malignancy, as was the case in our patient. The classic histologic features of SKs include acanthosis, papillomatosis, and hyperkeratosis.²² 

This case highlights the need to consider apocrine hidrocystoma, along with malignancy, in the differential diagnosis of pigmented cystic masses of the face and scalp. Because apocrine hidrocystomas are benign, they do not need to be treated but often are surgically excised for cosmesis or complete histopathologic examination. Destruction via electrodessication, carbon dioxide ablation, trichloroacetic acid chemical ablation, botulinum toxin injection, and anticholinergic creams sometimes is used, especially for cosmetic treatment of multiple small lesions.⁵ Our patient was treated with surgical excision with no evidence of recurrence on follow-up 1 year later. 

THE DIAGNOSIS: Pembrolizumab-Induced Eruptive Squamous Proliferation

Histopathology showed a broad squamous proliferation with acanthosis of the epidermis. Large glassy keratinocytes were seen with scattered necrotic keratinocytes (Figure), and a dense lichenoid band of inflammation was present subjacent to the proliferation. Notably, no hypergranulosis, remarkable keratinocyte atypia, or increased mitotic figures were seen. Based on the patient’s medical history and biopsy results, a diagnosis of pembrolizumab-induced eruptive squamous proliferation was made. The diagnosis was supported by a growing body of evidence of this type of reaction in patients taking programmed death 1 (PD-1) inhibitors.^1,2 Conservative treatment with clobetasol ointment 0.05% was initiated with complete resolution of the lesions at the 2-month follow-up appointment. Other common treatments include topical steroids, injected corticosteroids, or cryosurgery to locally control the inflammation and atypical proliferation of cells.³

Pembrolizumab is a humanized IgG4 monoclonal antibody targeting the PD-1 receptor that has been utilized for its antitumor activity against various cancers, including unresectable and metastatic melanoma, head and neck cancers, and non–small cell lung cancer (NSCLC).^1,4,5 While this drug has extended the lives of many patients with cancer, there are adverse reactions associated with PD-1 inhibitors (eg, pembrolizumab, nivolumab). Skin toxicity to PD-1 inhibitors is the one of most common immune-mediated reactions worldwide, occurring in approximately 30% of patients.^6,7 Reactions can occur while a patient is taking the inciting drug and can continue up to 2 months after treatment discontinuation.⁸ Skin reactions associated with PD-1 inhibitors vary from lichenoid reactions and vitiligolike patches to psoriasis or eczema flares and are organized into 4 categories: inflammatory, immunobullous, alteration of keratinocytes, and alteration of melanocytes.⁹ Our patient demonstrated alteration of keratinocytes, which is characterized by overlapping features of hypertrophic lichen planus and early keratoacanthoma.

The differential diagnoses for pembrolizumab-induced eruptive squamous proliferation include squamous cell carcinoma (SCC), psoriasis, hypertrophic lichen planus, and cutaneous metastasis of NSCLC. Hypertrophic lupus erythematosus also is a well-documented reaction to use of immune-checkpoint inhibitors.¹⁰ Direct immunofluorescence could have helped differentiate hypertrophic lupus erythematosus from an eruptive squamous proliferation in our patient; however, due to her response to treatment, no additional workup was done.

Squamous cell carcinoma, which is the most common type of skin cancer in Black patients in the United States,¹¹ has been shown to manifest after a PD-1 inhibitor is taken.¹² Although it typically has a more chronic persistent course, the clinical appearance of SCC can be similar to the findings seen in our patient. Histologically, SCC may demonstrate necrosis, but the atypical proliferations will invade the dermis—a feature not seen in our patient’s histopathology.¹³

Lichen planus (LP) is an eruptive immune reaction of violaceous polygonal papules and plaques commonly seen on the ankles¹⁴ that has been shown to be an adverse effect of pembrolizumab.¹⁵ There are several subtypes of LP including hypertrophic versions, which can appear clinically similar to the findings seen in our patient. On dermoscopy, the classic finding of white lines, known as Wickham striae, is seen in all subtypes and can help diagnose this pathologic process. Under the microscope, LP can manifest with hyperkeratosis without parakeratosis, irregular thickening of the stratum granulosum, sawtooth rete ridges, and destruction of the basal layer.¹⁴

Psoriasis also has been shown to be exacerbated by anti–PD-1 therapy, although the majority of patients diagnosed with PD-1–induced psoriasis have a personal or family history of the disease.⁶ Clinically, psoriasis can have a hyperpigmented or violaceous appearance in patients with skin of color.¹⁶ The histopathology of psoriasis typically reveals confluent parakeratosis, neutrophils in the stratum corneum, regular acanthosis, thinning of the suprapapillary plates, and vessels in the dermal papillae.¹⁷

Although cutaneous metastasis of NSCLC may appear clinically similar to the current case, it is one of the rarer organ sites of metastasis for lung cancer.¹⁸ In our patient, biopsy quickly ruled out this diagnosis. If it had been a site of metastasis, histopathology would have shown a dermal-based proliferation of dysplastic cells without epidermal connection.¹⁹

It is important for dermatologists to recognize eruptive squamous proliferations associated with pembrolizumab, as they often respond to conservative treatment and typically do not require dose reduction or discontinuation of the inciting drug.

THE DIAGNOSIS: Pembrolizumab-Induced Eruptive Squamous Proliferation

Histopathology showed a broad squamous proliferation with acanthosis of the epidermis. Large glassy keratinocytes were seen with scattered necrotic keratinocytes (Figure), and a dense lichenoid band of inflammation was present subjacent to the proliferation. Notably, no hypergranulosis, remarkable keratinocyte atypia, or increased mitotic figures were seen. Based on the patient’s medical history and biopsy results, a diagnosis of pembrolizumab-induced eruptive squamous proliferation was made. The diagnosis was supported by a growing body of evidence of this type of reaction in patients taking programmed death 1 (PD-1) inhibitors.^1,2 Conservative treatment with clobetasol ointment 0.05% was initiated with complete resolution of the lesions at the 2-month follow-up appointment. Other common treatments include topical steroids, injected corticosteroids, or cryosurgery to locally control the inflammation and atypical proliferation of cells.³

Pembrolizumab is a humanized IgG4 monoclonal antibody targeting the PD-1 receptor that has been utilized for its antitumor activity against various cancers, including unresectable and metastatic melanoma, head and neck cancers, and non–small cell lung cancer (NSCLC).^1,4,5 While this drug has extended the lives of many patients with cancer, there are adverse reactions associated with PD-1 inhibitors (eg, pembrolizumab, nivolumab). Skin toxicity to PD-1 inhibitors is the one of most common immune-mediated reactions worldwide, occurring in approximately 30% of patients.^6,7 Reactions can occur while a patient is taking the inciting drug and can continue up to 2 months after treatment discontinuation.⁸ Skin reactions associated with PD-1 inhibitors vary from lichenoid reactions and vitiligolike patches to psoriasis or eczema flares and are organized into 4 categories: inflammatory, immunobullous, alteration of keratinocytes, and alteration of melanocytes.⁹ Our patient demonstrated alteration of keratinocytes, which is characterized by overlapping features of hypertrophic lichen planus and early keratoacanthoma.

The differential diagnoses for pembrolizumab-induced eruptive squamous proliferation include squamous cell carcinoma (SCC), psoriasis, hypertrophic lichen planus, and cutaneous metastasis of NSCLC. Hypertrophic lupus erythematosus also is a well-documented reaction to use of immune-checkpoint inhibitors.¹⁰ Direct immunofluorescence could have helped differentiate hypertrophic lupus erythematosus from an eruptive squamous proliferation in our patient; however, due to her response to treatment, no additional workup was done.

Squamous cell carcinoma, which is the most common type of skin cancer in Black patients in the United States,¹¹ has been shown to manifest after a PD-1 inhibitor is taken.¹² Although it typically has a more chronic persistent course, the clinical appearance of SCC can be similar to the findings seen in our patient. Histologically, SCC may demonstrate necrosis, but the atypical proliferations will invade the dermis—a feature not seen in our patient’s histopathology.¹³

Lichen planus (LP) is an eruptive immune reaction of violaceous polygonal papules and plaques commonly seen on the ankles¹⁴ that has been shown to be an adverse effect of pembrolizumab.¹⁵ There are several subtypes of LP including hypertrophic versions, which can appear clinically similar to the findings seen in our patient. On dermoscopy, the classic finding of white lines, known as Wickham striae, is seen in all subtypes and can help diagnose this pathologic process. Under the microscope, LP can manifest with hyperkeratosis without parakeratosis, irregular thickening of the stratum granulosum, sawtooth rete ridges, and destruction of the basal layer.¹⁴

Psoriasis also has been shown to be exacerbated by anti–PD-1 therapy, although the majority of patients diagnosed with PD-1–induced psoriasis have a personal or family history of the disease.⁶ Clinically, psoriasis can have a hyperpigmented or violaceous appearance in patients with skin of color.¹⁶ The histopathology of psoriasis typically reveals confluent parakeratosis, neutrophils in the stratum corneum, regular acanthosis, thinning of the suprapapillary plates, and vessels in the dermal papillae.¹⁷

Although cutaneous metastasis of NSCLC may appear clinically similar to the current case, it is one of the rarer organ sites of metastasis for lung cancer.¹⁸ In our patient, biopsy quickly ruled out this diagnosis. If it had been a site of metastasis, histopathology would have shown a dermal-based proliferation of dysplastic cells without epidermal connection.¹⁹

It is important for dermatologists to recognize eruptive squamous proliferations associated with pembrolizumab, as they often respond to conservative treatment and typically do not require dose reduction or discontinuation of the inciting drug.

THE DIAGNOSIS: Pembrolizumab-Induced Eruptive Squamous Proliferation

Histopathology showed a broad squamous proliferation with acanthosis of the epidermis. Large glassy keratinocytes were seen with scattered necrotic keratinocytes (Figure), and a dense lichenoid band of inflammation was present subjacent to the proliferation. Notably, no hypergranulosis, remarkable keratinocyte atypia, or increased mitotic figures were seen. Based on the patient’s medical history and biopsy results, a diagnosis of pembrolizumab-induced eruptive squamous proliferation was made. The diagnosis was supported by a growing body of evidence of this type of reaction in patients taking programmed death 1 (PD-1) inhibitors.^1,2 Conservative treatment with clobetasol ointment 0.05% was initiated with complete resolution of the lesions at the 2-month follow-up appointment. Other common treatments include topical steroids, injected corticosteroids, or cryosurgery to locally control the inflammation and atypical proliferation of cells.³

Pembrolizumab is a humanized IgG4 monoclonal antibody targeting the PD-1 receptor that has been utilized for its antitumor activity against various cancers, including unresectable and metastatic melanoma, head and neck cancers, and non–small cell lung cancer (NSCLC).^1,4,5 While this drug has extended the lives of many patients with cancer, there are adverse reactions associated with PD-1 inhibitors (eg, pembrolizumab, nivolumab). Skin toxicity to PD-1 inhibitors is the one of most common immune-mediated reactions worldwide, occurring in approximately 30% of patients.^6,7 Reactions can occur while a patient is taking the inciting drug and can continue up to 2 months after treatment discontinuation.⁸ Skin reactions associated with PD-1 inhibitors vary from lichenoid reactions and vitiligolike patches to psoriasis or eczema flares and are organized into 4 categories: inflammatory, immunobullous, alteration of keratinocytes, and alteration of melanocytes.⁹ Our patient demonstrated alteration of keratinocytes, which is characterized by overlapping features of hypertrophic lichen planus and early keratoacanthoma.

The differential diagnoses for pembrolizumab-induced eruptive squamous proliferation include squamous cell carcinoma (SCC), psoriasis, hypertrophic lichen planus, and cutaneous metastasis of NSCLC. Hypertrophic lupus erythematosus also is a well-documented reaction to use of immune-checkpoint inhibitors.¹⁰ Direct immunofluorescence could have helped differentiate hypertrophic lupus erythematosus from an eruptive squamous proliferation in our patient; however, due to her response to treatment, no additional workup was done.

Squamous cell carcinoma, which is the most common type of skin cancer in Black patients in the United States,¹¹ has been shown to manifest after a PD-1 inhibitor is taken.¹² Although it typically has a more chronic persistent course, the clinical appearance of SCC can be similar to the findings seen in our patient. Histologically, SCC may demonstrate necrosis, but the atypical proliferations will invade the dermis—a feature not seen in our patient’s histopathology.¹³

Lichen planus (LP) is an eruptive immune reaction of violaceous polygonal papules and plaques commonly seen on the ankles¹⁴ that has been shown to be an adverse effect of pembrolizumab.¹⁵ There are several subtypes of LP including hypertrophic versions, which can appear clinically similar to the findings seen in our patient. On dermoscopy, the classic finding of white lines, known as Wickham striae, is seen in all subtypes and can help diagnose this pathologic process. Under the microscope, LP can manifest with hyperkeratosis without parakeratosis, irregular thickening of the stratum granulosum, sawtooth rete ridges, and destruction of the basal layer.¹⁴

Psoriasis also has been shown to be exacerbated by anti–PD-1 therapy, although the majority of patients diagnosed with PD-1–induced psoriasis have a personal or family history of the disease.⁶ Clinically, psoriasis can have a hyperpigmented or violaceous appearance in patients with skin of color.¹⁶ The histopathology of psoriasis typically reveals confluent parakeratosis, neutrophils in the stratum corneum, regular acanthosis, thinning of the suprapapillary plates, and vessels in the dermal papillae.¹⁷

Although cutaneous metastasis of NSCLC may appear clinically similar to the current case, it is one of the rarer organ sites of metastasis for lung cancer.¹⁸ In our patient, biopsy quickly ruled out this diagnosis. If it had been a site of metastasis, histopathology would have shown a dermal-based proliferation of dysplastic cells without epidermal connection.¹⁹

It is important for dermatologists to recognize eruptive squamous proliferations associated with pembrolizumab, as they often respond to conservative treatment and typically do not require dose reduction or discontinuation of the inciting drug.

THE DIAGNOSIS: Borderline-Borderline Leprosy With Type 1 Lepra Reaction

Punch biopsies from plaques on the right elbow and right shin revealed diffuse granulomatous dermatitis (Figure 1) with a narrow Grenz zone in the superficial dermis. The upper dermis contained a dense bandlike infiltrate of histiocytes with abundant foamy-gray cytoplasm and a moderate admixture of lymphocytes. The mid and deep dermis contained a nodular, perivascular, periadnexal, and perineural infiltrate of histiocytes and a dense admixture of lymphocytes. Periodic acid-Schiff and Gram stains were negative for microorganisms. Fite stain was positive for numerous organisms in histiocytes and small dermal nerves (Figure 2). These findings and the clinical examination confirmed a diagnosis of borderline-borderline leprosy with type 1 lepra reaction. The patient was started on dapsone 100 mg, rifampin 600 mg, and clofazimine 100 mg once daily and experienced clinical improvement within 6 months.

The World Health Organization reported more than 200,000 new leprosy cases globally in 2019, with most occurring in India, Brazil, and Indonesia.¹ About 150 to 250 new cases are detected in the United States annually.¹ The Ridley-Jopling classification of leprosy divides the condition into 5 categories: tuberculoid, borderline tuberculoid, borderline-borderline (BB), borderline lepromatous, and lepromatous. At one end of the spectrum, tuberculoid leprosy—a predominant Th1 immune response mediated by CD4 lymphocytes, interleukin (IL) 2, and interferon gamma²—is characterized by sharply demarcated erythematous and hypopigmented plaques with raised borders and an annular appearance.^2,3 Lesions typically have atrophic and hypopigmented centers that often appear in an asymmetric distribution on the arms and legs.^2,3 Histologic features include dermal tuberculoid granulomas with epithelioid cells—some located directly beneath the epidermis and others around deep vessels and nerves³—multinucleated Langerhans giant cells, thickened peripheral nerves with intraneural lymphocytic infiltrates, and granulomas with central necrosis. Fite-Faraco staining exhibits few bacteria.²

Lepromatous leprosy occurs in individuals with impaired T-cell immunity, leading to multiple red-brown nodular infiltrates in the skin and mucous membranes.^2,3 Lesions typically are symmetric and favor the face and auricle of the ear.^2,3 Histologically, there are bluish-gray foamy macrophages that form diffuse or nodular infiltrates with few lymphocytes,² with a Grenz zone between the epidermis and dermis. Nerves may show lamination of the perineurium resembling an onion skin.^2,3 Immunohistochemistry shows predominant CD8-positive infiltrates with a Th2 response and positive IL-4 and IL-10. Fite-Faraco stain shows numerous mycobacteria arranged in clusters and in histiocytes.²

Tuberculoid leprosy is treated with dapsone 100 mg and rifampin 600 mg once daily for 6 months,⁴ and lepromatous leprosy is treated with dapsone 100 mg, rifampin 600 mg, and clofazimine 50 mg once daily for 12 months.⁴ The prognosis for both is good with treatment; erythema and induration of skin lesions may improve within a few months, but residual nerve damage is common, especially in those with advanced disease prior to treatment.² For direct contacts, a single dose of rifampin may be given.⁴

Borderline-borderline leprosy manifests with numerous asymmetric annular plaques, as seen in our patient (Figure 3). Histology findings can be variable and often overlap with other forms of leprosy. There can be epithelioid granulomas and only a few acid-fast bacilli (AFB) or diffuse histiocytic aggregates with foamy histiocytes containing large numbers of AFB.³ Nerve involvement is variable but can be severe in the setting of type 1 lepra reaction, which was present in our patient. Type 1 lepra reaction—a type IV cell-mediated allergic hypersensitivity reaction to Mycobacterium leprae antigens—manifests clinically with hyperesthesia, erythema, edema, and subsequent scaling.² It occurs in up to 30% of patients with borderline leprosy, usually within 12 months of treatment initiation.² Our patient had considerable edema and erythema of the hands and feet (Figure 4) along with extensive polyneuropathy prior to starting therapy.

Lucio phenomenon is a rare leprosy reaction found in patients with untreated lepromatous leprosy characterized by erythematous to violaceous macules that lead to ulceronecrotic lesions.⁵ Histologically, there are many AFB in the vascular endothelium, leukocytoclastic vasculitis, and ischemic epidermal necrosis.⁵ Our patient did not have ulcerative or necrotic lesions.

The classic skin lesions of psoriasis vulgaris can be described as well-demarcated pink plaques with white or silvery scales that usually are distributed symmetrically and often are found on extensor surfaces.⁶ Rapidly progressive lesions can be annular with normal skin in the center, mimicking the lesions seen in tuberculoid leprosy. Clinically, both psoriasis and tuberculoid forms of leprosy are sharply demarcated; however, psoriatic lesions often have micaceous overlying scale that is not present in leprosy. Characteristic histologic findings of psoriasis are hyperkeratosis, parakeratosis, and acanthosis of the epidermis with dilated blood vessels and a lymphocytic infiltrate, predominantly into the dermis.⁷ Psoriatic arthritis has a variable clinical course but tends to emerge 5 to 12 years after initial skin manifestation.⁸ Classic clinical symptoms include swelling, tenderness, stiffness, and pain in joints and surrounding tissues.⁸ Other than edema, our patient did not exhibit signs of psoriatic arthritis.

Sarcoidosis is a systemic autoimmune disease characterized by noncaseating epithelioid granulomas affecting various organs, with cutaneous manifestations present in approximately 30% of all cases. Cutaneous manifestations can be variable, including maculopapular lesions, plaques, and nodules.⁹ Differentiating between cutaneous sarcoidosis and tuberculoid leprosy can be challenging, as both are granulomatous processes; however, histology of sarcoidosis demonstrates noncaseating granulomas in the dermis and/or subcutaneous tissues without AFB9 compared to granulomas with necrotic centers in tuberculoid leprosy.

Cutaneous tuberculosis has variable morphologies. One subtype, lupus vulgaris, can manifest with violaceous, scaly, eroded plaques that could be confused for leprosy. Lupus vulgaris usually results from hematogenous or lymphatic seeding in individuals with high or moderate immunity to M tuberculosis.¹⁰

Histologically, the dermis has tuberculoid granulomas containing multinucleated giant cells,¹⁰ which can mimic those seen in BB leprosy. Tuberculin skin test results often are positive¹⁰; while this test was not performed in our patient, chest radiography was unremarkable, making this diagnosis less likely.

Mycobacterium leprae infections should be considered in a patient with a worsening rash and progressive polyneuropathy. Clinical diagnosis can be challenging due to similarities with other diseases; however, histopathologic findings can help differentiate M leprae from other conditions. This infection is treatable, and early detection can minimize long-term patient morbidity.

THE DIAGNOSIS: Borderline-Borderline Leprosy With Type 1 Lepra Reaction

Punch biopsies from plaques on the right elbow and right shin revealed diffuse granulomatous dermatitis (Figure 1) with a narrow Grenz zone in the superficial dermis. The upper dermis contained a dense bandlike infiltrate of histiocytes with abundant foamy-gray cytoplasm and a moderate admixture of lymphocytes. The mid and deep dermis contained a nodular, perivascular, periadnexal, and perineural infiltrate of histiocytes and a dense admixture of lymphocytes. Periodic acid-Schiff and Gram stains were negative for microorganisms. Fite stain was positive for numerous organisms in histiocytes and small dermal nerves (Figure 2). These findings and the clinical examination confirmed a diagnosis of borderline-borderline leprosy with type 1 lepra reaction. The patient was started on dapsone 100 mg, rifampin 600 mg, and clofazimine 100 mg once daily and experienced clinical improvement within 6 months.

The World Health Organization reported more than 200,000 new leprosy cases globally in 2019, with most occurring in India, Brazil, and Indonesia.¹ About 150 to 250 new cases are detected in the United States annually.¹ The Ridley-Jopling classification of leprosy divides the condition into 5 categories: tuberculoid, borderline tuberculoid, borderline-borderline (BB), borderline lepromatous, and lepromatous. At one end of the spectrum, tuberculoid leprosy—a predominant Th1 immune response mediated by CD4 lymphocytes, interleukin (IL) 2, and interferon gamma²—is characterized by sharply demarcated erythematous and hypopigmented plaques with raised borders and an annular appearance.^2,3 Lesions typically have atrophic and hypopigmented centers that often appear in an asymmetric distribution on the arms and legs.^2,3 Histologic features include dermal tuberculoid granulomas with epithelioid cells—some located directly beneath the epidermis and others around deep vessels and nerves³—multinucleated Langerhans giant cells, thickened peripheral nerves with intraneural lymphocytic infiltrates, and granulomas with central necrosis. Fite-Faraco staining exhibits few bacteria.²

Lepromatous leprosy occurs in individuals with impaired T-cell immunity, leading to multiple red-brown nodular infiltrates in the skin and mucous membranes.^2,3 Lesions typically are symmetric and favor the face and auricle of the ear.^2,3 Histologically, there are bluish-gray foamy macrophages that form diffuse or nodular infiltrates with few lymphocytes,² with a Grenz zone between the epidermis and dermis. Nerves may show lamination of the perineurium resembling an onion skin.^2,3 Immunohistochemistry shows predominant CD8-positive infiltrates with a Th2 response and positive IL-4 and IL-10. Fite-Faraco stain shows numerous mycobacteria arranged in clusters and in histiocytes.²

Tuberculoid leprosy is treated with dapsone 100 mg and rifampin 600 mg once daily for 6 months,⁴ and lepromatous leprosy is treated with dapsone 100 mg, rifampin 600 mg, and clofazimine 50 mg once daily for 12 months.⁴ The prognosis for both is good with treatment; erythema and induration of skin lesions may improve within a few months, but residual nerve damage is common, especially in those with advanced disease prior to treatment.² For direct contacts, a single dose of rifampin may be given.⁴

Borderline-borderline leprosy manifests with numerous asymmetric annular plaques, as seen in our patient (Figure 3). Histology findings can be variable and often overlap with other forms of leprosy. There can be epithelioid granulomas and only a few acid-fast bacilli (AFB) or diffuse histiocytic aggregates with foamy histiocytes containing large numbers of AFB.³ Nerve involvement is variable but can be severe in the setting of type 1 lepra reaction, which was present in our patient. Type 1 lepra reaction—a type IV cell-mediated allergic hypersensitivity reaction to Mycobacterium leprae antigens—manifests clinically with hyperesthesia, erythema, edema, and subsequent scaling.² It occurs in up to 30% of patients with borderline leprosy, usually within 12 months of treatment initiation.² Our patient had considerable edema and erythema of the hands and feet (Figure 4) along with extensive polyneuropathy prior to starting therapy.

Lucio phenomenon is a rare leprosy reaction found in patients with untreated lepromatous leprosy characterized by erythematous to violaceous macules that lead to ulceronecrotic lesions.⁵ Histologically, there are many AFB in the vascular endothelium, leukocytoclastic vasculitis, and ischemic epidermal necrosis.⁵ Our patient did not have ulcerative or necrotic lesions.

The classic skin lesions of psoriasis vulgaris can be described as well-demarcated pink plaques with white or silvery scales that usually are distributed symmetrically and often are found on extensor surfaces.⁶ Rapidly progressive lesions can be annular with normal skin in the center, mimicking the lesions seen in tuberculoid leprosy. Clinically, both psoriasis and tuberculoid forms of leprosy are sharply demarcated; however, psoriatic lesions often have micaceous overlying scale that is not present in leprosy. Characteristic histologic findings of psoriasis are hyperkeratosis, parakeratosis, and acanthosis of the epidermis with dilated blood vessels and a lymphocytic infiltrate, predominantly into the dermis.⁷ Psoriatic arthritis has a variable clinical course but tends to emerge 5 to 12 years after initial skin manifestation.⁸ Classic clinical symptoms include swelling, tenderness, stiffness, and pain in joints and surrounding tissues.⁸ Other than edema, our patient did not exhibit signs of psoriatic arthritis.

Sarcoidosis is a systemic autoimmune disease characterized by noncaseating epithelioid granulomas affecting various organs, with cutaneous manifestations present in approximately 30% of all cases. Cutaneous manifestations can be variable, including maculopapular lesions, plaques, and nodules.⁹ Differentiating between cutaneous sarcoidosis and tuberculoid leprosy can be challenging, as both are granulomatous processes; however, histology of sarcoidosis demonstrates noncaseating granulomas in the dermis and/or subcutaneous tissues without AFB9 compared to granulomas with necrotic centers in tuberculoid leprosy.

Cutaneous tuberculosis has variable morphologies. One subtype, lupus vulgaris, can manifest with violaceous, scaly, eroded plaques that could be confused for leprosy. Lupus vulgaris usually results from hematogenous or lymphatic seeding in individuals with high or moderate immunity to M tuberculosis.¹⁰

Histologically, the dermis has tuberculoid granulomas containing multinucleated giant cells,¹⁰ which can mimic those seen in BB leprosy. Tuberculin skin test results often are positive¹⁰; while this test was not performed in our patient, chest radiography was unremarkable, making this diagnosis less likely.

Mycobacterium leprae infections should be considered in a patient with a worsening rash and progressive polyneuropathy. Clinical diagnosis can be challenging due to similarities with other diseases; however, histopathologic findings can help differentiate M leprae from other conditions. This infection is treatable, and early detection can minimize long-term patient morbidity.

THE DIAGNOSIS: Borderline-Borderline Leprosy With Type 1 Lepra Reaction

Punch biopsies from plaques on the right elbow and right shin revealed diffuse granulomatous dermatitis (Figure 1) with a narrow Grenz zone in the superficial dermis. The upper dermis contained a dense bandlike infiltrate of histiocytes with abundant foamy-gray cytoplasm and a moderate admixture of lymphocytes. The mid and deep dermis contained a nodular, perivascular, periadnexal, and perineural infiltrate of histiocytes and a dense admixture of lymphocytes. Periodic acid-Schiff and Gram stains were negative for microorganisms. Fite stain was positive for numerous organisms in histiocytes and small dermal nerves (Figure 2). These findings and the clinical examination confirmed a diagnosis of borderline-borderline leprosy with type 1 lepra reaction. The patient was started on dapsone 100 mg, rifampin 600 mg, and clofazimine 100 mg once daily and experienced clinical improvement within 6 months.

The World Health Organization reported more than 200,000 new leprosy cases globally in 2019, with most occurring in India, Brazil, and Indonesia.¹ About 150 to 250 new cases are detected in the United States annually.¹ The Ridley-Jopling classification of leprosy divides the condition into 5 categories: tuberculoid, borderline tuberculoid, borderline-borderline (BB), borderline lepromatous, and lepromatous. At one end of the spectrum, tuberculoid leprosy—a predominant Th1 immune response mediated by CD4 lymphocytes, interleukin (IL) 2, and interferon gamma²—is characterized by sharply demarcated erythematous and hypopigmented plaques with raised borders and an annular appearance.^2,3 Lesions typically have atrophic and hypopigmented centers that often appear in an asymmetric distribution on the arms and legs.^2,3 Histologic features include dermal tuberculoid granulomas with epithelioid cells—some located directly beneath the epidermis and others around deep vessels and nerves³—multinucleated Langerhans giant cells, thickened peripheral nerves with intraneural lymphocytic infiltrates, and granulomas with central necrosis. Fite-Faraco staining exhibits few bacteria.²

Lepromatous leprosy occurs in individuals with impaired T-cell immunity, leading to multiple red-brown nodular infiltrates in the skin and mucous membranes.^2,3 Lesions typically are symmetric and favor the face and auricle of the ear.^2,3 Histologically, there are bluish-gray foamy macrophages that form diffuse or nodular infiltrates with few lymphocytes,² with a Grenz zone between the epidermis and dermis. Nerves may show lamination of the perineurium resembling an onion skin.^2,3 Immunohistochemistry shows predominant CD8-positive infiltrates with a Th2 response and positive IL-4 and IL-10. Fite-Faraco stain shows numerous mycobacteria arranged in clusters and in histiocytes.²

Tuberculoid leprosy is treated with dapsone 100 mg and rifampin 600 mg once daily for 6 months,⁴ and lepromatous leprosy is treated with dapsone 100 mg, rifampin 600 mg, and clofazimine 50 mg once daily for 12 months.⁴ The prognosis for both is good with treatment; erythema and induration of skin lesions may improve within a few months, but residual nerve damage is common, especially in those with advanced disease prior to treatment.² For direct contacts, a single dose of rifampin may be given.⁴

Borderline-borderline leprosy manifests with numerous asymmetric annular plaques, as seen in our patient (Figure 3). Histology findings can be variable and often overlap with other forms of leprosy. There can be epithelioid granulomas and only a few acid-fast bacilli (AFB) or diffuse histiocytic aggregates with foamy histiocytes containing large numbers of AFB.³ Nerve involvement is variable but can be severe in the setting of type 1 lepra reaction, which was present in our patient. Type 1 lepra reaction—a type IV cell-mediated allergic hypersensitivity reaction to Mycobacterium leprae antigens—manifests clinically with hyperesthesia, erythema, edema, and subsequent scaling.² It occurs in up to 30% of patients with borderline leprosy, usually within 12 months of treatment initiation.² Our patient had considerable edema and erythema of the hands and feet (Figure 4) along with extensive polyneuropathy prior to starting therapy.

Lucio phenomenon is a rare leprosy reaction found in patients with untreated lepromatous leprosy characterized by erythematous to violaceous macules that lead to ulceronecrotic lesions.⁵ Histologically, there are many AFB in the vascular endothelium, leukocytoclastic vasculitis, and ischemic epidermal necrosis.⁵ Our patient did not have ulcerative or necrotic lesions.

The classic skin lesions of psoriasis vulgaris can be described as well-demarcated pink plaques with white or silvery scales that usually are distributed symmetrically and often are found on extensor surfaces.⁶ Rapidly progressive lesions can be annular with normal skin in the center, mimicking the lesions seen in tuberculoid leprosy. Clinically, both psoriasis and tuberculoid forms of leprosy are sharply demarcated; however, psoriatic lesions often have micaceous overlying scale that is not present in leprosy. Characteristic histologic findings of psoriasis are hyperkeratosis, parakeratosis, and acanthosis of the epidermis with dilated blood vessels and a lymphocytic infiltrate, predominantly into the dermis.⁷ Psoriatic arthritis has a variable clinical course but tends to emerge 5 to 12 years after initial skin manifestation.⁸ Classic clinical symptoms include swelling, tenderness, stiffness, and pain in joints and surrounding tissues.⁸ Other than edema, our patient did not exhibit signs of psoriatic arthritis.

Sarcoidosis is a systemic autoimmune disease characterized by noncaseating epithelioid granulomas affecting various organs, with cutaneous manifestations present in approximately 30% of all cases. Cutaneous manifestations can be variable, including maculopapular lesions, plaques, and nodules.⁹ Differentiating between cutaneous sarcoidosis and tuberculoid leprosy can be challenging, as both are granulomatous processes; however, histology of sarcoidosis demonstrates noncaseating granulomas in the dermis and/or subcutaneous tissues without AFB9 compared to granulomas with necrotic centers in tuberculoid leprosy.

Cutaneous tuberculosis has variable morphologies. One subtype, lupus vulgaris, can manifest with violaceous, scaly, eroded plaques that could be confused for leprosy. Lupus vulgaris usually results from hematogenous or lymphatic seeding in individuals with high or moderate immunity to M tuberculosis.¹⁰

Histologically, the dermis has tuberculoid granulomas containing multinucleated giant cells,¹⁰ which can mimic those seen in BB leprosy. Tuberculin skin test results often are positive¹⁰; while this test was not performed in our patient, chest radiography was unremarkable, making this diagnosis less likely.

Mycobacterium leprae infections should be considered in a patient with a worsening rash and progressive polyneuropathy. Clinical diagnosis can be challenging due to similarities with other diseases; however, histopathologic findings can help differentiate M leprae from other conditions. This infection is treatable, and early detection can minimize long-term patient morbidity.

THE DIAGNOSIS: Lichen Sclerosus

Given the clinical appearance of white atrophic plaques with characteristic wrinkling of the skin, a diagnosis of lichen sclerosus was strongly suspected. At the initial office visit, the patient was prescribed clobetasol 0.05% ointment twice daily for 6 weeks. Histopathology revealed hyperkeratosis, follicular plugging, papillary dermal pallor, and adjacent lymphocytic inflammation, confirming the clinical diagnosis of lichen sclerosus (Figure). The patient then was lost to follow-up.

Lichen sclerosus is a chronic benign dermatologic condition of unknown etiology that is characterized by epidermal atrophy and inflammation and is common in postmenopausal women. It features pale, ivory-colored lesions with partially atrophic skin and a wrinkled cigarette paper appearance.¹ The differential for lichen sclerosus is broad, and definitive diagnosis is made via biopsy to rule out potential malignancy and other inflammatory skin diseases.¹ Lichen sclerosus is an immune-mediated disorder driven by type 1 T helper cells and regulated by miR-155. There has been an association with extracellular matrix protein 1, a glycoprotein that is found in the dermal-epidermal basement membrane zone, which provides structural integrity to the skin. Autoantibodies against extracellular matrix protein 1 and other antigens in the basement membrane generally are found in anogenital lichen sclerosus; however, their precise roles in the pathogenesis of lichen sclerosus remains unclear.¹

The differential diagnoses for lichen sclerosus include psoriasis, tinea corporis, lichen simplex chronicus, and atopic dermatitis. Psoriasis typically manifests as pink plaques with silver scales on the elbows, knees, and scalp in adult patients.² Our patient’s white plaques may have suggested psoriasis, but the partially atrophic skin with a wrinkled cigarette paper appearance was not compatible with that diagnosis.

Tinea corporis, a superficial fungal infection of the skin, manifests as circular or ovoid lesions with raised erythematous scaly borders, often with central clearing resembling a ring, that can occur anywhere on the body other than the feet, groin, face, scalp, or beard area.³ The fact that our patient previously had tried topical antifungal medications with no relief and that the skin lesions were atrophic rather than ring shaped made the diagnosis of tinea corporis unlikely.

Lichen simplex chronicus is a chronic condition caused by friction or scratching that is characterized by dry, patchy, scaly, and thickened areas of the skin. Typically affecting the head, arms, neck, scalp, and genital region, lichen simplex chronicus manifests with violaceous or hyperpigmented lesions.⁴ The nonpruritic atrophic plaques on the inner thighs and the presence of white patches on the vaginal area were not indicative of lichen simplex chronicus in our patient.

Atopic dermatitis manifests as pruritic erythematous scaly papules and plaques with secondary excoriation and possible lichenification. In adults, atopic dermatitis commonly appears on flexural surfaces.² Atopic dermatitis does not manifest with atrophy and skin wrinkling as seen in our patient.

In the management of lichen sclerosus, the standard treatment is potent topical corticosteroids. Alternatively, topical calcineurin inhibitors can be employed; however, due to the unknown nature of the condition’s underlying cause, targeted treatment is challenging. Our case underscores how lichen sclerosus can be misdiagnosed, highlighting the need for more frequent reporting in the literature to enhance early recognition and reduce delays in patient treatment.

THE DIAGNOSIS: Lichen Sclerosus

Given the clinical appearance of white atrophic plaques with characteristic wrinkling of the skin, a diagnosis of lichen sclerosus was strongly suspected. At the initial office visit, the patient was prescribed clobetasol 0.05% ointment twice daily for 6 weeks. Histopathology revealed hyperkeratosis, follicular plugging, papillary dermal pallor, and adjacent lymphocytic inflammation, confirming the clinical diagnosis of lichen sclerosus (Figure). The patient then was lost to follow-up.

Lichen sclerosus is a chronic benign dermatologic condition of unknown etiology that is characterized by epidermal atrophy and inflammation and is common in postmenopausal women. It features pale, ivory-colored lesions with partially atrophic skin and a wrinkled cigarette paper appearance.¹ The differential for lichen sclerosus is broad, and definitive diagnosis is made via biopsy to rule out potential malignancy and other inflammatory skin diseases.¹ Lichen sclerosus is an immune-mediated disorder driven by type 1 T helper cells and regulated by miR-155. There has been an association with extracellular matrix protein 1, a glycoprotein that is found in the dermal-epidermal basement membrane zone, which provides structural integrity to the skin. Autoantibodies against extracellular matrix protein 1 and other antigens in the basement membrane generally are found in anogenital lichen sclerosus; however, their precise roles in the pathogenesis of lichen sclerosus remains unclear.¹

The differential diagnoses for lichen sclerosus include psoriasis, tinea corporis, lichen simplex chronicus, and atopic dermatitis. Psoriasis typically manifests as pink plaques with silver scales on the elbows, knees, and scalp in adult patients.² Our patient’s white plaques may have suggested psoriasis, but the partially atrophic skin with a wrinkled cigarette paper appearance was not compatible with that diagnosis.

Tinea corporis, a superficial fungal infection of the skin, manifests as circular or ovoid lesions with raised erythematous scaly borders, often with central clearing resembling a ring, that can occur anywhere on the body other than the feet, groin, face, scalp, or beard area.³ The fact that our patient previously had tried topical antifungal medications with no relief and that the skin lesions were atrophic rather than ring shaped made the diagnosis of tinea corporis unlikely.

Lichen simplex chronicus is a chronic condition caused by friction or scratching that is characterized by dry, patchy, scaly, and thickened areas of the skin. Typically affecting the head, arms, neck, scalp, and genital region, lichen simplex chronicus manifests with violaceous or hyperpigmented lesions.⁴ The nonpruritic atrophic plaques on the inner thighs and the presence of white patches on the vaginal area were not indicative of lichen simplex chronicus in our patient.

Atopic dermatitis manifests as pruritic erythematous scaly papules and plaques with secondary excoriation and possible lichenification. In adults, atopic dermatitis commonly appears on flexural surfaces.² Atopic dermatitis does not manifest with atrophy and skin wrinkling as seen in our patient.

In the management of lichen sclerosus, the standard treatment is potent topical corticosteroids. Alternatively, topical calcineurin inhibitors can be employed; however, due to the unknown nature of the condition’s underlying cause, targeted treatment is challenging. Our case underscores how lichen sclerosus can be misdiagnosed, highlighting the need for more frequent reporting in the literature to enhance early recognition and reduce delays in patient treatment.

THE DIAGNOSIS: Lichen Sclerosus

Given the clinical appearance of white atrophic plaques with characteristic wrinkling of the skin, a diagnosis of lichen sclerosus was strongly suspected. At the initial office visit, the patient was prescribed clobetasol 0.05% ointment twice daily for 6 weeks. Histopathology revealed hyperkeratosis, follicular plugging, papillary dermal pallor, and adjacent lymphocytic inflammation, confirming the clinical diagnosis of lichen sclerosus (Figure). The patient then was lost to follow-up.

Lichen sclerosus is a chronic benign dermatologic condition of unknown etiology that is characterized by epidermal atrophy and inflammation and is common in postmenopausal women. It features pale, ivory-colored lesions with partially atrophic skin and a wrinkled cigarette paper appearance.¹ The differential for lichen sclerosus is broad, and definitive diagnosis is made via biopsy to rule out potential malignancy and other inflammatory skin diseases.¹ Lichen sclerosus is an immune-mediated disorder driven by type 1 T helper cells and regulated by miR-155. There has been an association with extracellular matrix protein 1, a glycoprotein that is found in the dermal-epidermal basement membrane zone, which provides structural integrity to the skin. Autoantibodies against extracellular matrix protein 1 and other antigens in the basement membrane generally are found in anogenital lichen sclerosus; however, their precise roles in the pathogenesis of lichen sclerosus remains unclear.¹

The differential diagnoses for lichen sclerosus include psoriasis, tinea corporis, lichen simplex chronicus, and atopic dermatitis. Psoriasis typically manifests as pink plaques with silver scales on the elbows, knees, and scalp in adult patients.² Our patient’s white plaques may have suggested psoriasis, but the partially atrophic skin with a wrinkled cigarette paper appearance was not compatible with that diagnosis.

Tinea corporis, a superficial fungal infection of the skin, manifests as circular or ovoid lesions with raised erythematous scaly borders, often with central clearing resembling a ring, that can occur anywhere on the body other than the feet, groin, face, scalp, or beard area.³ The fact that our patient previously had tried topical antifungal medications with no relief and that the skin lesions were atrophic rather than ring shaped made the diagnosis of tinea corporis unlikely.

Lichen simplex chronicus is a chronic condition caused by friction or scratching that is characterized by dry, patchy, scaly, and thickened areas of the skin. Typically affecting the head, arms, neck, scalp, and genital region, lichen simplex chronicus manifests with violaceous or hyperpigmented lesions.⁴ The nonpruritic atrophic plaques on the inner thighs and the presence of white patches on the vaginal area were not indicative of lichen simplex chronicus in our patient.

Atopic dermatitis manifests as pruritic erythematous scaly papules and plaques with secondary excoriation and possible lichenification. In adults, atopic dermatitis commonly appears on flexural surfaces.² Atopic dermatitis does not manifest with atrophy and skin wrinkling as seen in our patient.

In the management of lichen sclerosus, the standard treatment is potent topical corticosteroids. Alternatively, topical calcineurin inhibitors can be employed; however, due to the unknown nature of the condition’s underlying cause, targeted treatment is challenging. Our case underscores how lichen sclerosus can be misdiagnosed, highlighting the need for more frequent reporting in the literature to enhance early recognition and reduce delays in patient treatment.