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The Diagnosis: Acrodermatitis Continua of Hallopeau

Acrodermatitis continua of Hallopeau (ACH) is considered to be a form of acropustular psoriasis that presents as a sterile, pustular eruption initially affecting the fingertips and/or toes.¹ The slow-growing pustules typically progress locally and can lead to onychodystrophy and/or osteolysis of the underlying bone.^2,3 Most commonly affecting adult women, ACH often begins following local trauma to or infection of a single digit.⁴ As the disease progresses proximally, the small pustules burst, leaving a shiny, erythematous surface on which new pustules can develop. These pustules have a tendency to amalgamate, leading to the characteristic clinical finding of lakes of pus. Pustules frequently appear on the nail matrix and nail bed presenting as severe onychodystrophy and ultimately anonychia.^5,6 Rarely, ACH can be associated with generalized pustular psoriasis as well as conjunctivitis, balanitis, and fissuring or annulus migrans of the tongue.^2,7

Diagnosis can be established based on clinical findings, biopsy, and bacterial and fungal cultures revealing sterile pustules.^8,9 Histologic findings are similar to those seen in pustular psoriasis, demonstrating subcorneal neutrophilic pustules, Munro microabscesses, and dilated blood vessels with lymphocytic infiltrate in the papillary dermis.¹⁰

Due to the refractory nature of the disease, there are no recommended guidelines for treatment of ACH. Most successful treatment regimens consist of topical psoriasis medications combined with systemic psoriatic therapies such as cyclosporine, methotrexate, acitretin, or biologic therapy.^8,11-16 Our patient achieved satisfactory clinical improvement with clobetasol propionate ointment 0.05% twice daily alternating with calcipotriene cream 0.005% twice daily.

The Diagnosis: Acrodermatitis Continua of Hallopeau

Acrodermatitis continua of Hallopeau (ACH) is considered to be a form of acropustular psoriasis that presents as a sterile, pustular eruption initially affecting the fingertips and/or toes.¹ The slow-growing pustules typically progress locally and can lead to onychodystrophy and/or osteolysis of the underlying bone.^2,3 Most commonly affecting adult women, ACH often begins following local trauma to or infection of a single digit.⁴ As the disease progresses proximally, the small pustules burst, leaving a shiny, erythematous surface on which new pustules can develop. These pustules have a tendency to amalgamate, leading to the characteristic clinical finding of lakes of pus. Pustules frequently appear on the nail matrix and nail bed presenting as severe onychodystrophy and ultimately anonychia.^5,6 Rarely, ACH can be associated with generalized pustular psoriasis as well as conjunctivitis, balanitis, and fissuring or annulus migrans of the tongue.^2,7

Diagnosis can be established based on clinical findings, biopsy, and bacterial and fungal cultures revealing sterile pustules.^8,9 Histologic findings are similar to those seen in pustular psoriasis, demonstrating subcorneal neutrophilic pustules, Munro microabscesses, and dilated blood vessels with lymphocytic infiltrate in the papillary dermis.¹⁰

Due to the refractory nature of the disease, there are no recommended guidelines for treatment of ACH. Most successful treatment regimens consist of topical psoriasis medications combined with systemic psoriatic therapies such as cyclosporine, methotrexate, acitretin, or biologic therapy.^8,11-16 Our patient achieved satisfactory clinical improvement with clobetasol propionate ointment 0.05% twice daily alternating with calcipotriene cream 0.005% twice daily.

The Diagnosis: Acrodermatitis Continua of Hallopeau

Acrodermatitis continua of Hallopeau (ACH) is considered to be a form of acropustular psoriasis that presents as a sterile, pustular eruption initially affecting the fingertips and/or toes.¹ The slow-growing pustules typically progress locally and can lead to onychodystrophy and/or osteolysis of the underlying bone.^2,3 Most commonly affecting adult women, ACH often begins following local trauma to or infection of a single digit.⁴ As the disease progresses proximally, the small pustules burst, leaving a shiny, erythematous surface on which new pustules can develop. These pustules have a tendency to amalgamate, leading to the characteristic clinical finding of lakes of pus. Pustules frequently appear on the nail matrix and nail bed presenting as severe onychodystrophy and ultimately anonychia.^5,6 Rarely, ACH can be associated with generalized pustular psoriasis as well as conjunctivitis, balanitis, and fissuring or annulus migrans of the tongue.^2,7

Diagnosis can be established based on clinical findings, biopsy, and bacterial and fungal cultures revealing sterile pustules.^8,9 Histologic findings are similar to those seen in pustular psoriasis, demonstrating subcorneal neutrophilic pustules, Munro microabscesses, and dilated blood vessels with lymphocytic infiltrate in the papillary dermis.¹⁰

Due to the refractory nature of the disease, there are no recommended guidelines for treatment of ACH. Most successful treatment regimens consist of topical psoriasis medications combined with systemic psoriatic therapies such as cyclosporine, methotrexate, acitretin, or biologic therapy.^8,11-16 Our patient achieved satisfactory clinical improvement with clobetasol propionate ointment 0.05% twice daily alternating with calcipotriene cream 0.005% twice daily.

The Diagnosis: Tinea Corporis

Although contact dermatitis from the metal on the back of the watch was suspected, many modern wrist watches are made with stainless steel rather than nickel, which is a common contact allergen; therefore, other diagnoses were considered in the differential including irritant contact dermatitis, psoriasis, and tinea infection. A potassium hydroxide (KOH) preparation was performed to rule out tinea infection. Unexpectedly, the KOH preparation was positive for fungal hyphae, confirming a diagnosis of tinea corporis. The patient was treated with clotrimazole cream 1% twice daily for 3 weeks during which time the rash completely resolved.

We present this case to stress the importance of performing KOH preparations even when the likelihood of tinea infection seems remote. At our institution, we teach our residents, “If it’s scaly, scrape it.” This adage has served us well. Tinea corporis may be mistaken for many other skin diseases, including eczema, psoriasis, and seborrheic dermatitis.¹ A KOH preparation often is a helpful tool in confirming the diagnosis and should be performed when a dermatophyte infection is suspected. The KOH preparation is the most sensitive diagnostic test used to confirm dermatophyte infection, with 90% of infections showing positive results.^2,3

Tinea infections may occur anywhere on the body, but areas that are prone to excessive heat and/or moisture are particularly susceptible.⁴ Dermatophyte infections typically present as annular, scaly, pruritic patches or plaques often with central clearing and an active border.¹ In our patient, the lesion showed characteristics that were suggestive of a dermatophyte infection but was somewhat atypical in appearance, as it lacked central clearing (Figure). The 3 genera of dermatophytes—Trichophyton, Microsporum, and Epidermophyton—are common causes of fungal infections.² The pathogenesis of dermatophytosis is the synthesis of keratinases that digest keratin and sustain the presence of the fungi. Local factors such as sweating and occlusion facilitate the activity of these organisms.² In our case, the pathogenesis was believed to be due to the entrapment of moisture behind the patient’s watch, creating a favorable environment for fungal growth.

The Diagnosis: Tinea Corporis

Although contact dermatitis from the metal on the back of the watch was suspected, many modern wrist watches are made with stainless steel rather than nickel, which is a common contact allergen; therefore, other diagnoses were considered in the differential including irritant contact dermatitis, psoriasis, and tinea infection. A potassium hydroxide (KOH) preparation was performed to rule out tinea infection. Unexpectedly, the KOH preparation was positive for fungal hyphae, confirming a diagnosis of tinea corporis. The patient was treated with clotrimazole cream 1% twice daily for 3 weeks during which time the rash completely resolved.

We present this case to stress the importance of performing KOH preparations even when the likelihood of tinea infection seems remote. At our institution, we teach our residents, “If it’s scaly, scrape it.” This adage has served us well. Tinea corporis may be mistaken for many other skin diseases, including eczema, psoriasis, and seborrheic dermatitis.¹ A KOH preparation often is a helpful tool in confirming the diagnosis and should be performed when a dermatophyte infection is suspected. The KOH preparation is the most sensitive diagnostic test used to confirm dermatophyte infection, with 90% of infections showing positive results.^2,3

Tinea infections may occur anywhere on the body, but areas that are prone to excessive heat and/or moisture are particularly susceptible.⁴ Dermatophyte infections typically present as annular, scaly, pruritic patches or plaques often with central clearing and an active border.¹ In our patient, the lesion showed characteristics that were suggestive of a dermatophyte infection but was somewhat atypical in appearance, as it lacked central clearing (Figure). The 3 genera of dermatophytes—Trichophyton, Microsporum, and Epidermophyton—are common causes of fungal infections.² The pathogenesis of dermatophytosis is the synthesis of keratinases that digest keratin and sustain the presence of the fungi. Local factors such as sweating and occlusion facilitate the activity of these organisms.² In our case, the pathogenesis was believed to be due to the entrapment of moisture behind the patient’s watch, creating a favorable environment for fungal growth.

The Diagnosis: Tinea Corporis

Although contact dermatitis from the metal on the back of the watch was suspected, many modern wrist watches are made with stainless steel rather than nickel, which is a common contact allergen; therefore, other diagnoses were considered in the differential including irritant contact dermatitis, psoriasis, and tinea infection. A potassium hydroxide (KOH) preparation was performed to rule out tinea infection. Unexpectedly, the KOH preparation was positive for fungal hyphae, confirming a diagnosis of tinea corporis. The patient was treated with clotrimazole cream 1% twice daily for 3 weeks during which time the rash completely resolved.

We present this case to stress the importance of performing KOH preparations even when the likelihood of tinea infection seems remote. At our institution, we teach our residents, “If it’s scaly, scrape it.” This adage has served us well. Tinea corporis may be mistaken for many other skin diseases, including eczema, psoriasis, and seborrheic dermatitis.¹ A KOH preparation often is a helpful tool in confirming the diagnosis and should be performed when a dermatophyte infection is suspected. The KOH preparation is the most sensitive diagnostic test used to confirm dermatophyte infection, with 90% of infections showing positive results.^2,3

Tinea infections may occur anywhere on the body, but areas that are prone to excessive heat and/or moisture are particularly susceptible.⁴ Dermatophyte infections typically present as annular, scaly, pruritic patches or plaques often with central clearing and an active border.¹ In our patient, the lesion showed characteristics that were suggestive of a dermatophyte infection but was somewhat atypical in appearance, as it lacked central clearing (Figure). The 3 genera of dermatophytes—Trichophyton, Microsporum, and Epidermophyton—are common causes of fungal infections.² The pathogenesis of dermatophytosis is the synthesis of keratinases that digest keratin and sustain the presence of the fungi. Local factors such as sweating and occlusion facilitate the activity of these organisms.² In our case, the pathogenesis was believed to be due to the entrapment of moisture behind the patient’s watch, creating a favorable environment for fungal growth.

The Diagnosis: Agminated Blue Nevus

Agminated blue nevus is a rare melanocytic nevus that characteristically presents as a group of multiple small, bluish papules occurring in a well-circumscribed area.¹ It also has been referred to as a plaque-type nevus^2,3 and an eruptive blue nevus.⁴ Originally described by Upshaw et al² in 1947, agminated blue nevi may be congenital or arise in early childhood and almost always occur on the trunk. The skin between the papules often is unaffected or sometimes may show bluish or brown pigmentation.⁴ Agminated blue nevi usually are smaller than 10 cm in diameter; however, rare cases have measured up to 24 cm.^1,4-6 The incidence of agminated blue nevi is 2 times higher in males than in females.¹

A biopsy of the lesion revealed pigmented dendritic melanocytes admixed with melanophages, forming fascicles and bundles (A)(H&E, original magnification ×10). In some areas the dermis was uninvolved. Higher magnification showed dendritic and epithelioid melanocytes extending down along the adnexal structures (B)(H&E, original magnification ×40).

Histopathologically, agminated blue nevi typically demonstrate the features of common and/or cellular blue nevi. Cytologic atypia and mitoses are rare.¹ The degree of cellularity and pigmentation of the lesions is variable, and the presence of subcutaneous cellular nodules also has been described.⁵

In our patient, histologic evaluation revealed foci of diffuse dermal spindle cell proliferation composed of heavily pigmented dendritic melanocytes admixed with melanophages in a fibrotic stroma (Figure, A). The dermis was uninvolved in some areas and the melanocytes were epithelioid and formed fascicles and bundles that extended down adnexal structures in other areas (Figure, B). Junctional involvement of melanocytes, cellular atypia, and mitoses were not identified. Our case demonstrated a combination of histologic findings of a cellular blue nevus as well as features reminiscent of a deep penetrating nevus. The differential diagnosis of agminated blue nevus includes agminated Spitz nevus arising in a speckled lentiginous nevus,⁷ dermal melanocytosis, melanoma, and pilar neurocristic hamartoma. Pilar neurocristic hamartomas may resemble plaque-type blue nevi; however, the former show a predilection for the scalp, histologically demonstrate features that overlap with blue nevi and congenital nevi, and are associated with neural structures that show Schwannian differentiation.⁸ Agminated blue nevi usually are characterized by a benign clinical course, but few cases describing malignant changes with development of malignant melanoma have been reported.^9,10 Therefore, recognition of the clinical and histopathologic spectrum of agminated blue nevus is critical in order to avoid diagnostic pitfalls and confusion with melanoma.

The Diagnosis: Agminated Blue Nevus

Agminated blue nevus is a rare melanocytic nevus that characteristically presents as a group of multiple small, bluish papules occurring in a well-circumscribed area.¹ It also has been referred to as a plaque-type nevus^2,3 and an eruptive blue nevus.⁴ Originally described by Upshaw et al² in 1947, agminated blue nevi may be congenital or arise in early childhood and almost always occur on the trunk. The skin between the papules often is unaffected or sometimes may show bluish or brown pigmentation.⁴ Agminated blue nevi usually are smaller than 10 cm in diameter; however, rare cases have measured up to 24 cm.^1,4-6 The incidence of agminated blue nevi is 2 times higher in males than in females.¹

A biopsy of the lesion revealed pigmented dendritic melanocytes admixed with melanophages, forming fascicles and bundles (A)(H&E, original magnification ×10). In some areas the dermis was uninvolved. Higher magnification showed dendritic and epithelioid melanocytes extending down along the adnexal structures (B)(H&E, original magnification ×40).

Histopathologically, agminated blue nevi typically demonstrate the features of common and/or cellular blue nevi. Cytologic atypia and mitoses are rare.¹ The degree of cellularity and pigmentation of the lesions is variable, and the presence of subcutaneous cellular nodules also has been described.⁵

In our patient, histologic evaluation revealed foci of diffuse dermal spindle cell proliferation composed of heavily pigmented dendritic melanocytes admixed with melanophages in a fibrotic stroma (Figure, A). The dermis was uninvolved in some areas and the melanocytes were epithelioid and formed fascicles and bundles that extended down adnexal structures in other areas (Figure, B). Junctional involvement of melanocytes, cellular atypia, and mitoses were not identified. Our case demonstrated a combination of histologic findings of a cellular blue nevus as well as features reminiscent of a deep penetrating nevus. The differential diagnosis of agminated blue nevus includes agminated Spitz nevus arising in a speckled lentiginous nevus,⁷ dermal melanocytosis, melanoma, and pilar neurocristic hamartoma. Pilar neurocristic hamartomas may resemble plaque-type blue nevi; however, the former show a predilection for the scalp, histologically demonstrate features that overlap with blue nevi and congenital nevi, and are associated with neural structures that show Schwannian differentiation.⁸ Agminated blue nevi usually are characterized by a benign clinical course, but few cases describing malignant changes with development of malignant melanoma have been reported.^9,10 Therefore, recognition of the clinical and histopathologic spectrum of agminated blue nevus is critical in order to avoid diagnostic pitfalls and confusion with melanoma.

The Diagnosis: Agminated Blue Nevus

Agminated blue nevus is a rare melanocytic nevus that characteristically presents as a group of multiple small, bluish papules occurring in a well-circumscribed area.¹ It also has been referred to as a plaque-type nevus^2,3 and an eruptive blue nevus.⁴ Originally described by Upshaw et al² in 1947, agminated blue nevi may be congenital or arise in early childhood and almost always occur on the trunk. The skin between the papules often is unaffected or sometimes may show bluish or brown pigmentation.⁴ Agminated blue nevi usually are smaller than 10 cm in diameter; however, rare cases have measured up to 24 cm.^1,4-6 The incidence of agminated blue nevi is 2 times higher in males than in females.¹

A biopsy of the lesion revealed pigmented dendritic melanocytes admixed with melanophages, forming fascicles and bundles (A)(H&E, original magnification ×10). In some areas the dermis was uninvolved. Higher magnification showed dendritic and epithelioid melanocytes extending down along the adnexal structures (B)(H&E, original magnification ×40).

Histopathologically, agminated blue nevi typically demonstrate the features of common and/or cellular blue nevi. Cytologic atypia and mitoses are rare.¹ The degree of cellularity and pigmentation of the lesions is variable, and the presence of subcutaneous cellular nodules also has been described.⁵

In our patient, histologic evaluation revealed foci of diffuse dermal spindle cell proliferation composed of heavily pigmented dendritic melanocytes admixed with melanophages in a fibrotic stroma (Figure, A). The dermis was uninvolved in some areas and the melanocytes were epithelioid and formed fascicles and bundles that extended down adnexal structures in other areas (Figure, B). Junctional involvement of melanocytes, cellular atypia, and mitoses were not identified. Our case demonstrated a combination of histologic findings of a cellular blue nevus as well as features reminiscent of a deep penetrating nevus. The differential diagnosis of agminated blue nevus includes agminated Spitz nevus arising in a speckled lentiginous nevus,⁷ dermal melanocytosis, melanoma, and pilar neurocristic hamartoma. Pilar neurocristic hamartomas may resemble plaque-type blue nevi; however, the former show a predilection for the scalp, histologically demonstrate features that overlap with blue nevi and congenital nevi, and are associated with neural structures that show Schwannian differentiation.⁸ Agminated blue nevi usually are characterized by a benign clinical course, but few cases describing malignant changes with development of malignant melanoma have been reported.^9,10 Therefore, recognition of the clinical and histopathologic spectrum of agminated blue nevus is critical in order to avoid diagnostic pitfalls and confusion with melanoma.

The Diagnosis: Eccrine Poroma

A shave biopsy of the lesion was performed for definitive diagnosis and demonstrated a well-circumscribed tumor with cords and broad columns composed of uniform basaloid cells extending into the dermis and in areas connecting to the overlying epidermis (Figure). There also were small ducts and cysts admixed in the tumor columns that were embedded in a tumor stroma rich in blood vessels. A diagnosis of eccrine poroma was made based on these characteristic histologic features.

Biopsy revealed a basaloid tumor originating from the epidermis and extending into the dermis (A)(H&E, original magnification ×4). On higher magnification, ducts were evident amongst the tumor cells and a vascular rich stroma was revealed (B)(H&E, original magnification ×10).

First described by Pinkus et al¹ in 1956, eccrine poroma is a benign neoplasm of cells from the intraepidermal ductal portion of the eccrine sweat gland. Eccrine poroma (along with hidroacanthoma simplex, dermal duct tumor, and poroid hidradenoma) is one of the poroid neoplasms, which account for approximately 10% of all primary sweat gland tumors.² Eccrine poroma usually is seen in patients over 40 years of age without any predilection for race or sex.

Characteristically, eccrine poromas clinically manifest as solitary, firm, sharply demarcated papules or nodules that may be sessile or pedunculated and rarely exceed 2 cm in diameter. This entity classically presents on acral, non–hair-bearing areas (eg, palms and soles). Eccrine poromas have a wide range of clinical appearances that can lead to broad differential diagnoses³ and have been described as flesh-colored,³ pink to red,⁴ purple,⁵ and pigmented^3,4 papules or nodules depending on features such as blood vessel proliferation and pigment deposition.

Eccrine poromas also have been reported on hair-bearing areas of the body, including the head,³ neck,^3,6 chest,^4,6 hip,⁷ and pubic area,⁸ despite the paucity of eccrine glands in these areas on the body. These findings suggest that these neoplasms may not be purely eccrine in origin. The wide range of clinical presentations of eccrine poromas has prompted investigation into further classification and delineation of this neoplasm.³ The occurrence of eccrine poromas on areas of the skin known to have few eccrine glands suggests that eccrine poromas may not be purely comprised of eccrine ducts and instead may be of apocrine origin.^3,9,10 Histologic features of eccrine poromas that suggest apocrine origination include sebaceous and follicular differentiation (eg, folliculocentric distribution), the association with the follicular infundibulum, and the presence of follicular germ cells.^3,9,10 Thus, apocrine gland involvement in eccrine poromas may account for their appearance in anatomic areas that do not have high concentrations of eccrine glands, such as the trunk and pubic area.

Based on these findings, eccrine poromas may therefore be of eccrine and/or apocrine origin; however, the nomenclature of this neoplasm remains confusing and possibly misleading, as the term eccrine poroma continues to be accepted even in instances in which the differentiation appears to be largely apocrine. The terms poroma and eccrine poroma often are used interchangeably, which contributes to the confusion by failing to acknowledge the possibility of apocrine influence and possibly causing the clinician to exclude eccrine poromas from the differential diagnosis in areas that do not have high concentrations of eccrine glands.

Because of their high degree of clinical variability, characteristic acral location, and misleading nomenclature, eccrine poromas often are mistakenly confused with a long list of other cutaneous neoplasms, including hemangiomas, pyogenic granulomas, melanocytic nevi, warts, cysts, and other adnexal neoplasms.³ In our case, the lesion was abnormally large and was clinically concerning for an unusual sebaceous nevus. Its location on the lower back is not commonly noted and should remind the clinician of the possibility of apocrine differentiation. Clinicians should be aware of the wide phenotypic diversity of eccrine poromas, and therefore they should consider this diagnosis in their differential diagnosis for solitary papules or nodules occurring in any anatomic area.

The Diagnosis: Eccrine Poroma

A shave biopsy of the lesion was performed for definitive diagnosis and demonstrated a well-circumscribed tumor with cords and broad columns composed of uniform basaloid cells extending into the dermis and in areas connecting to the overlying epidermis (Figure). There also were small ducts and cysts admixed in the tumor columns that were embedded in a tumor stroma rich in blood vessels. A diagnosis of eccrine poroma was made based on these characteristic histologic features.

Biopsy revealed a basaloid tumor originating from the epidermis and extending into the dermis (A)(H&E, original magnification ×4). On higher magnification, ducts were evident amongst the tumor cells and a vascular rich stroma was revealed (B)(H&E, original magnification ×10).

First described by Pinkus et al¹ in 1956, eccrine poroma is a benign neoplasm of cells from the intraepidermal ductal portion of the eccrine sweat gland. Eccrine poroma (along with hidroacanthoma simplex, dermal duct tumor, and poroid hidradenoma) is one of the poroid neoplasms, which account for approximately 10% of all primary sweat gland tumors.² Eccrine poroma usually is seen in patients over 40 years of age without any predilection for race or sex.

Characteristically, eccrine poromas clinically manifest as solitary, firm, sharply demarcated papules or nodules that may be sessile or pedunculated and rarely exceed 2 cm in diameter. This entity classically presents on acral, non–hair-bearing areas (eg, palms and soles). Eccrine poromas have a wide range of clinical appearances that can lead to broad differential diagnoses³ and have been described as flesh-colored,³ pink to red,⁴ purple,⁵ and pigmented^3,4 papules or nodules depending on features such as blood vessel proliferation and pigment deposition.

Eccrine poromas also have been reported on hair-bearing areas of the body, including the head,³ neck,^3,6 chest,^4,6 hip,⁷ and pubic area,⁸ despite the paucity of eccrine glands in these areas on the body. These findings suggest that these neoplasms may not be purely eccrine in origin. The wide range of clinical presentations of eccrine poromas has prompted investigation into further classification and delineation of this neoplasm.³ The occurrence of eccrine poromas on areas of the skin known to have few eccrine glands suggests that eccrine poromas may not be purely comprised of eccrine ducts and instead may be of apocrine origin.^3,9,10 Histologic features of eccrine poromas that suggest apocrine origination include sebaceous and follicular differentiation (eg, folliculocentric distribution), the association with the follicular infundibulum, and the presence of follicular germ cells.^3,9,10 Thus, apocrine gland involvement in eccrine poromas may account for their appearance in anatomic areas that do not have high concentrations of eccrine glands, such as the trunk and pubic area.

Based on these findings, eccrine poromas may therefore be of eccrine and/or apocrine origin; however, the nomenclature of this neoplasm remains confusing and possibly misleading, as the term eccrine poroma continues to be accepted even in instances in which the differentiation appears to be largely apocrine. The terms poroma and eccrine poroma often are used interchangeably, which contributes to the confusion by failing to acknowledge the possibility of apocrine influence and possibly causing the clinician to exclude eccrine poromas from the differential diagnosis in areas that do not have high concentrations of eccrine glands.

Because of their high degree of clinical variability, characteristic acral location, and misleading nomenclature, eccrine poromas often are mistakenly confused with a long list of other cutaneous neoplasms, including hemangiomas, pyogenic granulomas, melanocytic nevi, warts, cysts, and other adnexal neoplasms.³ In our case, the lesion was abnormally large and was clinically concerning for an unusual sebaceous nevus. Its location on the lower back is not commonly noted and should remind the clinician of the possibility of apocrine differentiation. Clinicians should be aware of the wide phenotypic diversity of eccrine poromas, and therefore they should consider this diagnosis in their differential diagnosis for solitary papules or nodules occurring in any anatomic area.

The Diagnosis: Eccrine Poroma

A shave biopsy of the lesion was performed for definitive diagnosis and demonstrated a well-circumscribed tumor with cords and broad columns composed of uniform basaloid cells extending into the dermis and in areas connecting to the overlying epidermis (Figure). There also were small ducts and cysts admixed in the tumor columns that were embedded in a tumor stroma rich in blood vessels. A diagnosis of eccrine poroma was made based on these characteristic histologic features.

Biopsy revealed a basaloid tumor originating from the epidermis and extending into the dermis (A)(H&E, original magnification ×4). On higher magnification, ducts were evident amongst the tumor cells and a vascular rich stroma was revealed (B)(H&E, original magnification ×10).

First described by Pinkus et al¹ in 1956, eccrine poroma is a benign neoplasm of cells from the intraepidermal ductal portion of the eccrine sweat gland. Eccrine poroma (along with hidroacanthoma simplex, dermal duct tumor, and poroid hidradenoma) is one of the poroid neoplasms, which account for approximately 10% of all primary sweat gland tumors.² Eccrine poroma usually is seen in patients over 40 years of age without any predilection for race or sex.

Characteristically, eccrine poromas clinically manifest as solitary, firm, sharply demarcated papules or nodules that may be sessile or pedunculated and rarely exceed 2 cm in diameter. This entity classically presents on acral, non–hair-bearing areas (eg, palms and soles). Eccrine poromas have a wide range of clinical appearances that can lead to broad differential diagnoses³ and have been described as flesh-colored,³ pink to red,⁴ purple,⁵ and pigmented^3,4 papules or nodules depending on features such as blood vessel proliferation and pigment deposition.

Eccrine poromas also have been reported on hair-bearing areas of the body, including the head,³ neck,^3,6 chest,^4,6 hip,⁷ and pubic area,⁸ despite the paucity of eccrine glands in these areas on the body. These findings suggest that these neoplasms may not be purely eccrine in origin. The wide range of clinical presentations of eccrine poromas has prompted investigation into further classification and delineation of this neoplasm.³ The occurrence of eccrine poromas on areas of the skin known to have few eccrine glands suggests that eccrine poromas may not be purely comprised of eccrine ducts and instead may be of apocrine origin.^3,9,10 Histologic features of eccrine poromas that suggest apocrine origination include sebaceous and follicular differentiation (eg, folliculocentric distribution), the association with the follicular infundibulum, and the presence of follicular germ cells.^3,9,10 Thus, apocrine gland involvement in eccrine poromas may account for their appearance in anatomic areas that do not have high concentrations of eccrine glands, such as the trunk and pubic area.

Based on these findings, eccrine poromas may therefore be of eccrine and/or apocrine origin; however, the nomenclature of this neoplasm remains confusing and possibly misleading, as the term eccrine poroma continues to be accepted even in instances in which the differentiation appears to be largely apocrine. The terms poroma and eccrine poroma often are used interchangeably, which contributes to the confusion by failing to acknowledge the possibility of apocrine influence and possibly causing the clinician to exclude eccrine poromas from the differential diagnosis in areas that do not have high concentrations of eccrine glands.

Because of their high degree of clinical variability, characteristic acral location, and misleading nomenclature, eccrine poromas often are mistakenly confused with a long list of other cutaneous neoplasms, including hemangiomas, pyogenic granulomas, melanocytic nevi, warts, cysts, and other adnexal neoplasms.³ In our case, the lesion was abnormally large and was clinically concerning for an unusual sebaceous nevus. Its location on the lower back is not commonly noted and should remind the clinician of the possibility of apocrine differentiation. Clinicians should be aware of the wide phenotypic diversity of eccrine poromas, and therefore they should consider this diagnosis in their differential diagnosis for solitary papules or nodules occurring in any anatomic area.

The Diagnosis: Porokeratosis of Mibelli

There are 5 variants of porokeratosis: disseminated superficial actinic porokeratosis (DSAP), linear porokeratosis, porokeratosis of Mibelli, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis. The most common type is DSAP,¹ which is characterized by multiple lesions on the body, particularly in sun-exposed areas. The distinguishing feature of porokeratosis is the cornoid lamella, which is made up of parakeratotic cells extending through the stratum corneum. There also is a thin or absent granular layer beneath it (Figure).²

Patients generally present in the third and fourth decades of life.¹ Risk factors for porokeratosis include sun exposure, immunosuppression, and genetics.^2-4 Overexpression of the protein p53 in porokeratosis lesions has been demonstrated in studies investigating the genetics of porokeratosis.^5,6 A study of Chinese families with DSAP identified 3 different loci associated with DSAP: DSAP1, DSAP2, and DSAP3.² The progression to cancer has been noted in all types of porokeratosis lesions. Malignancies include squamous cell carcinoma, Bowen disease, and basal cell carcinoma.^7,8

Many treatments have been tried for DSAP including cryotherapy, topical 5-fluorouracil, photodynamic therapy, and topical imiquimod with varying success.¹ Our patient was treated with 
cryotherapy but had side effects from treatment including cellulitis and local infections with ulceration before finally healing.

Interestingly, our patient had a single lesion with pathology findings most consistent with DSAP at a later age. Although the pathology suggested DSAP, the size and solitary lesion was more consistent with porokeratosis of Mibelli. Porokeratosis of Mibelli can occur concurrently with DSAP,⁹ but we have not seen other lesions in this patient. We have educated our patient to be aware of other lesions that may occur in the future. Due to risk for malignant conversion, it is generally viewed as beneficial to treat patients who present with porokeratosis lesions. Our patient’s lesion ultimately cleared and he has not developed new lesions at 1-year follow-up.

Although DSAP generally presents in the third and fourth decades of life and porokeratosis of Mibelli during childhood, it is important to educate both dermatologists and primary care physicians to be aware of the possibility of both diagnoses in the elderly population.

The Diagnosis: Porokeratosis of Mibelli

There are 5 variants of porokeratosis: disseminated superficial actinic porokeratosis (DSAP), linear porokeratosis, porokeratosis of Mibelli, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis. The most common type is DSAP,¹ which is characterized by multiple lesions on the body, particularly in sun-exposed areas. The distinguishing feature of porokeratosis is the cornoid lamella, which is made up of parakeratotic cells extending through the stratum corneum. There also is a thin or absent granular layer beneath it (Figure).²

Patients generally present in the third and fourth decades of life.¹ Risk factors for porokeratosis include sun exposure, immunosuppression, and genetics.^2-4 Overexpression of the protein p53 in porokeratosis lesions has been demonstrated in studies investigating the genetics of porokeratosis.^5,6 A study of Chinese families with DSAP identified 3 different loci associated with DSAP: DSAP1, DSAP2, and DSAP3.² The progression to cancer has been noted in all types of porokeratosis lesions. Malignancies include squamous cell carcinoma, Bowen disease, and basal cell carcinoma.^7,8

Many treatments have been tried for DSAP including cryotherapy, topical 5-fluorouracil, photodynamic therapy, and topical imiquimod with varying success.¹ Our patient was treated with 
cryotherapy but had side effects from treatment including cellulitis and local infections with ulceration before finally healing.

Interestingly, our patient had a single lesion with pathology findings most consistent with DSAP at a later age. Although the pathology suggested DSAP, the size and solitary lesion was more consistent with porokeratosis of Mibelli. Porokeratosis of Mibelli can occur concurrently with DSAP,⁹ but we have not seen other lesions in this patient. We have educated our patient to be aware of other lesions that may occur in the future. Due to risk for malignant conversion, it is generally viewed as beneficial to treat patients who present with porokeratosis lesions. Our patient’s lesion ultimately cleared and he has not developed new lesions at 1-year follow-up.

Although DSAP generally presents in the third and fourth decades of life and porokeratosis of Mibelli during childhood, it is important to educate both dermatologists and primary care physicians to be aware of the possibility of both diagnoses in the elderly population.

The Diagnosis: Porokeratosis of Mibelli

There are 5 variants of porokeratosis: disseminated superficial actinic porokeratosis (DSAP), linear porokeratosis, porokeratosis of Mibelli, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis. The most common type is DSAP,¹ which is characterized by multiple lesions on the body, particularly in sun-exposed areas. The distinguishing feature of porokeratosis is the cornoid lamella, which is made up of parakeratotic cells extending through the stratum corneum. There also is a thin or absent granular layer beneath it (Figure).²

Patients generally present in the third and fourth decades of life.¹ Risk factors for porokeratosis include sun exposure, immunosuppression, and genetics.^2-4 Overexpression of the protein p53 in porokeratosis lesions has been demonstrated in studies investigating the genetics of porokeratosis.^5,6 A study of Chinese families with DSAP identified 3 different loci associated with DSAP: DSAP1, DSAP2, and DSAP3.² The progression to cancer has been noted in all types of porokeratosis lesions. Malignancies include squamous cell carcinoma, Bowen disease, and basal cell carcinoma.^7,8

Many treatments have been tried for DSAP including cryotherapy, topical 5-fluorouracil, photodynamic therapy, and topical imiquimod with varying success.¹ Our patient was treated with 
cryotherapy but had side effects from treatment including cellulitis and local infections with ulceration before finally healing.

Interestingly, our patient had a single lesion with pathology findings most consistent with DSAP at a later age. Although the pathology suggested DSAP, the size and solitary lesion was more consistent with porokeratosis of Mibelli. Porokeratosis of Mibelli can occur concurrently with DSAP,⁹ but we have not seen other lesions in this patient. We have educated our patient to be aware of other lesions that may occur in the future. Due to risk for malignant conversion, it is generally viewed as beneficial to treat patients who present with porokeratosis lesions. Our patient’s lesion ultimately cleared and he has not developed new lesions at 1-year follow-up.

Although DSAP generally presents in the third and fourth decades of life and porokeratosis of Mibelli during childhood, it is important to educate both dermatologists and primary care physicians to be aware of the possibility of both diagnoses in the elderly population.

The Diagnosis: Fixed Cutaneous Sporotrichosis

On further questioning at our dermatology clinic, the patient reported having landed face-first into rocks and gravel during the all-terrain vehicle accident. After his medical history was noted and a physical examination was completed, bacterial and fungal cultures of the wound were taken. The fungal culture was positive for Sporothrix schenckii. The patient was prescribed itraconazole 200 mg 3 times daily for 3 days, then 200 mg twice daily for an additional 4 weeks after the lesions completely resolved. An ophthalmologist was immediately consulted to rule out sinus and periorbital involvement. After computed tomography revealed possible preseptal cellulitis with frontal sinus involvement, the patient was admitted and intravenous amphotericin B was administered. Following consultations with infectious disease specialists and radiologists, amphotericin B was discontinued and the patient was discharged on itraconazole 200 mg twice daily with close monitoring. At 3-month follow-up, the sporotrichosis infection had completely cleared (Figure).

Deep fungal infections comprise 2 distinct groups: systemic and subcutaneous mycoses. Individuals with subcutaneous mycoses present with skin involvement as the primary feature. Sporotrichosis is the most common cause of this type of mycosis¹ and is caused by the dimorphic fungus S schenckii, an environmental saprophyte often residing in soil. Sporothrix schenckii exists as mold in a natural environment but exists as yeast in host tissue, thus causing ensuing infection.

Epidemiology

Sporotrichosis occurs worldwide but most frequently in temperate tropical and subtropical regions. The majority of cases are reported in Mexico and Central and South America¹; however, cases have been seen in the southern United States, Japan, and Australia.² In the United States, sporotrichosis is most commonly found in river valleys of the Midwest.

Sporothrix schenckii is most commonly isolated in hay, sphagnum moss, thorny plants, and soil, but it also has been described in other manifold host environments. Unusual origins of inoculation include an old and rust-stained camping tent in Mexico,³ crawl space joists of a house in Indiana,⁴ and hay bales used as props in a haunted house in Oklahoma.⁵

The incidence of infection is primarily sporadic; however, outbreaks among individuals who share a common environment favorable for the growth of S schenckii are at risk. Those identified to be at risk include rose gardeners, berry pickers, those who work in tree nurseries, horticulturists, landscapers, and miners.

Pathogenesis

As a dimorphic fungus, infection occurs when a conidium in the mold phase is introduced into the skin, usually by traumatic skin injury, and is 
converted to the yeast form in vivo. Distribution of infection by this organism is most commonly 
localized to the cutaneous, subcutaneous, and lymphocutaneous regions in healthy hosts but can involve visceral and osteoarticular structures in immunocompromised hosts.^1,6 Pulmonary and disseminated forms are rare but can occur when 
S schenckii conidia are inhaled. Zoonotic transmission of the fungus also can occur with exposure to infected animals. Sporothrix schenckii has been reported to occur in cats, dogs, horses, donkeys, squirrels, armadillos, and dolphins.^7-11

Pathology

Sporothrix schenckii is typically not visualized on microscopic examination due to the small number of microorganisms present; however, cultures grow rapidly 
(3–5 days) on Sabouraud agar. The fungus most commonly develops as white or off-white compact colonies that progressively darken with age, transitioning to gray and then black.¹ Microscopically, the hyphae produce oval or pyriform conidia, which are assembled 
in a typical bouquetlike manner. Conversion of the organism to yeast on enriched medium such as brain-heart infusion agar or blood-cysteine-glucose agar confirms the diagnosis.

Acute lesions typically show a nonspecific mixed infiltrate, but established lesions may reveal granulomatous formation and neutrophilic microabscesses.^1,2 Asteroid bodies, which are cigar-shaped yeasts surrounded by eosinophilic coronae radiata, may be found. Organisms are sparsely distributed within the lesions, necessitating a thorough examination of the culture for identification.

Clinical Features

Sporotrichosis has 3 main classifications: lymphocutaneous, fixed cutaneous, and disseminated. Lymphocutaneous sporotrichosis is the most common form of the infection.² The disease presents with a small indurated papule occurring approximately 7 to 30 days after inoculation into the skin. The papule slowly enlarges, forms a nodule, and then frequently ulcerates. Over time, draining lymphatics become edematous and inflammatory, and a chain of secondary nodules begins to appear proximal to the initial lesion. The primary and secondary nodules may continue to ulcerate; alternately, they may heal or become chronic.

In fixed cutaneous sporotrichosis, the infection remains localized to one region and a granuloma may develop, which also may ulcerate. Satellite nodules may appear along the periphery of the lesion. Lymphatic spread is not observed in this form of 
the disease.

The disseminated form is a result of hematogenous spread from the primary inoculation site and typically occurs in an immunocompromised host. This form can present as pulmonary disease, sinusitis, and meningitis.¹

Differential Diagnosis

The differential diagnosis for sporotrichosis includes atypical mycobacteria, nocardiosis, blastomycosis, pyogenic bacteria, leishmaniasis, tularemia, 
and tuberculosis.

Treatment

Treatment of sporotrichosis is always required. A saturated solution of potassium iodide has classically been used; however, it is frequently associated with side effects and can be problematic to administer.¹² Given its low cost and traditional efficacy, it may still be used in some parts of the world.

Currently, the treatment of choice for fixed cutaneous and lymphocutaneous sporotrichosis is itraconazole 100 to 200 mg once daily for 3 to 6 months.¹ The recommended treatment of osteoarticular sporotrichosis is itraconazole, but prolonged therapy is required.

Heat therapy is an alternative treatment option, as certain strains of S schenckii do not grow at temperatures higher than 35°C. Hot compresses must be used for at least 1 hour a day for several months, which may affect patient compliance.

Immunocompromised patients often have disseminated infection and require lifelong suppressive therapy with itraconazole and may require initial treatment with amphotericin B.¹³

Conclusion

Subcutaneous sporotrichosis can develop in patients with a traumatic injury involving vegetation, soil, or animals. Although some patients may develop more invasive disease, most infections in immunocompetent patients will resolve after 3 to 6 months of itraconazole 100 to 200 mg once daily.¹

The Diagnosis: Fixed Cutaneous Sporotrichosis

On further questioning at our dermatology clinic, the patient reported having landed face-first into rocks and gravel during the all-terrain vehicle accident. After his medical history was noted and a physical examination was completed, bacterial and fungal cultures of the wound were taken. The fungal culture was positive for Sporothrix schenckii. The patient was prescribed itraconazole 200 mg 3 times daily for 3 days, then 200 mg twice daily for an additional 4 weeks after the lesions completely resolved. An ophthalmologist was immediately consulted to rule out sinus and periorbital involvement. After computed tomography revealed possible preseptal cellulitis with frontal sinus involvement, the patient was admitted and intravenous amphotericin B was administered. Following consultations with infectious disease specialists and radiologists, amphotericin B was discontinued and the patient was discharged on itraconazole 200 mg twice daily with close monitoring. At 3-month follow-up, the sporotrichosis infection had completely cleared (Figure).

Deep fungal infections comprise 2 distinct groups: systemic and subcutaneous mycoses. Individuals with subcutaneous mycoses present with skin involvement as the primary feature. Sporotrichosis is the most common cause of this type of mycosis¹ and is caused by the dimorphic fungus S schenckii, an environmental saprophyte often residing in soil. Sporothrix schenckii exists as mold in a natural environment but exists as yeast in host tissue, thus causing ensuing infection.

Epidemiology

Sporotrichosis occurs worldwide but most frequently in temperate tropical and subtropical regions. The majority of cases are reported in Mexico and Central and South America¹; however, cases have been seen in the southern United States, Japan, and Australia.² In the United States, sporotrichosis is most commonly found in river valleys of the Midwest.

Sporothrix schenckii is most commonly isolated in hay, sphagnum moss, thorny plants, and soil, but it also has been described in other manifold host environments. Unusual origins of inoculation include an old and rust-stained camping tent in Mexico,³ crawl space joists of a house in Indiana,⁴ and hay bales used as props in a haunted house in Oklahoma.⁵

The incidence of infection is primarily sporadic; however, outbreaks among individuals who share a common environment favorable for the growth of S schenckii are at risk. Those identified to be at risk include rose gardeners, berry pickers, those who work in tree nurseries, horticulturists, landscapers, and miners.

Pathogenesis

As a dimorphic fungus, infection occurs when a conidium in the mold phase is introduced into the skin, usually by traumatic skin injury, and is 
converted to the yeast form in vivo. Distribution of infection by this organism is most commonly 
localized to the cutaneous, subcutaneous, and lymphocutaneous regions in healthy hosts but can involve visceral and osteoarticular structures in immunocompromised hosts.^1,6 Pulmonary and disseminated forms are rare but can occur when 
S schenckii conidia are inhaled. Zoonotic transmission of the fungus also can occur with exposure to infected animals. Sporothrix schenckii has been reported to occur in cats, dogs, horses, donkeys, squirrels, armadillos, and dolphins.^7-11

Pathology

Sporothrix schenckii is typically not visualized on microscopic examination due to the small number of microorganisms present; however, cultures grow rapidly 
(3–5 days) on Sabouraud agar. The fungus most commonly develops as white or off-white compact colonies that progressively darken with age, transitioning to gray and then black.¹ Microscopically, the hyphae produce oval or pyriform conidia, which are assembled 
in a typical bouquetlike manner. Conversion of the organism to yeast on enriched medium such as brain-heart infusion agar or blood-cysteine-glucose agar confirms the diagnosis.

Acute lesions typically show a nonspecific mixed infiltrate, but established lesions may reveal granulomatous formation and neutrophilic microabscesses.^1,2 Asteroid bodies, which are cigar-shaped yeasts surrounded by eosinophilic coronae radiata, may be found. Organisms are sparsely distributed within the lesions, necessitating a thorough examination of the culture for identification.

Clinical Features

Sporotrichosis has 3 main classifications: lymphocutaneous, fixed cutaneous, and disseminated. Lymphocutaneous sporotrichosis is the most common form of the infection.² The disease presents with a small indurated papule occurring approximately 7 to 30 days after inoculation into the skin. The papule slowly enlarges, forms a nodule, and then frequently ulcerates. Over time, draining lymphatics become edematous and inflammatory, and a chain of secondary nodules begins to appear proximal to the initial lesion. The primary and secondary nodules may continue to ulcerate; alternately, they may heal or become chronic.

In fixed cutaneous sporotrichosis, the infection remains localized to one region and a granuloma may develop, which also may ulcerate. Satellite nodules may appear along the periphery of the lesion. Lymphatic spread is not observed in this form of 
the disease.

The disseminated form is a result of hematogenous spread from the primary inoculation site and typically occurs in an immunocompromised host. This form can present as pulmonary disease, sinusitis, and meningitis.¹

Differential Diagnosis

The differential diagnosis for sporotrichosis includes atypical mycobacteria, nocardiosis, blastomycosis, pyogenic bacteria, leishmaniasis, tularemia, 
and tuberculosis.

Treatment

Treatment of sporotrichosis is always required. A saturated solution of potassium iodide has classically been used; however, it is frequently associated with side effects and can be problematic to administer.¹² Given its low cost and traditional efficacy, it may still be used in some parts of the world.

Currently, the treatment of choice for fixed cutaneous and lymphocutaneous sporotrichosis is itraconazole 100 to 200 mg once daily for 3 to 6 months.¹ The recommended treatment of osteoarticular sporotrichosis is itraconazole, but prolonged therapy is required.

Heat therapy is an alternative treatment option, as certain strains of S schenckii do not grow at temperatures higher than 35°C. Hot compresses must be used for at least 1 hour a day for several months, which may affect patient compliance.

Immunocompromised patients often have disseminated infection and require lifelong suppressive therapy with itraconazole and may require initial treatment with amphotericin B.¹³

Conclusion

Subcutaneous sporotrichosis can develop in patients with a traumatic injury involving vegetation, soil, or animals. Although some patients may develop more invasive disease, most infections in immunocompetent patients will resolve after 3 to 6 months of itraconazole 100 to 200 mg once daily.¹

The Diagnosis: Fixed Cutaneous Sporotrichosis

On further questioning at our dermatology clinic, the patient reported having landed face-first into rocks and gravel during the all-terrain vehicle accident. After his medical history was noted and a physical examination was completed, bacterial and fungal cultures of the wound were taken. The fungal culture was positive for Sporothrix schenckii. The patient was prescribed itraconazole 200 mg 3 times daily for 3 days, then 200 mg twice daily for an additional 4 weeks after the lesions completely resolved. An ophthalmologist was immediately consulted to rule out sinus and periorbital involvement. After computed tomography revealed possible preseptal cellulitis with frontal sinus involvement, the patient was admitted and intravenous amphotericin B was administered. Following consultations with infectious disease specialists and radiologists, amphotericin B was discontinued and the patient was discharged on itraconazole 200 mg twice daily with close monitoring. At 3-month follow-up, the sporotrichosis infection had completely cleared (Figure).

Deep fungal infections comprise 2 distinct groups: systemic and subcutaneous mycoses. Individuals with subcutaneous mycoses present with skin involvement as the primary feature. Sporotrichosis is the most common cause of this type of mycosis¹ and is caused by the dimorphic fungus S schenckii, an environmental saprophyte often residing in soil. Sporothrix schenckii exists as mold in a natural environment but exists as yeast in host tissue, thus causing ensuing infection.

Epidemiology

Sporotrichosis occurs worldwide but most frequently in temperate tropical and subtropical regions. The majority of cases are reported in Mexico and Central and South America¹; however, cases have been seen in the southern United States, Japan, and Australia.² In the United States, sporotrichosis is most commonly found in river valleys of the Midwest.

Sporothrix schenckii is most commonly isolated in hay, sphagnum moss, thorny plants, and soil, but it also has been described in other manifold host environments. Unusual origins of inoculation include an old and rust-stained camping tent in Mexico,³ crawl space joists of a house in Indiana,⁴ and hay bales used as props in a haunted house in Oklahoma.⁵

The incidence of infection is primarily sporadic; however, outbreaks among individuals who share a common environment favorable for the growth of S schenckii are at risk. Those identified to be at risk include rose gardeners, berry pickers, those who work in tree nurseries, horticulturists, landscapers, and miners.

Pathogenesis

As a dimorphic fungus, infection occurs when a conidium in the mold phase is introduced into the skin, usually by traumatic skin injury, and is 
converted to the yeast form in vivo. Distribution of infection by this organism is most commonly 
localized to the cutaneous, subcutaneous, and lymphocutaneous regions in healthy hosts but can involve visceral and osteoarticular structures in immunocompromised hosts.^1,6 Pulmonary and disseminated forms are rare but can occur when 
S schenckii conidia are inhaled. Zoonotic transmission of the fungus also can occur with exposure to infected animals. Sporothrix schenckii has been reported to occur in cats, dogs, horses, donkeys, squirrels, armadillos, and dolphins.^7-11

Pathology

Sporothrix schenckii is typically not visualized on microscopic examination due to the small number of microorganisms present; however, cultures grow rapidly 
(3–5 days) on Sabouraud agar. The fungus most commonly develops as white or off-white compact colonies that progressively darken with age, transitioning to gray and then black.¹ Microscopically, the hyphae produce oval or pyriform conidia, which are assembled 
in a typical bouquetlike manner. Conversion of the organism to yeast on enriched medium such as brain-heart infusion agar or blood-cysteine-glucose agar confirms the diagnosis.

Acute lesions typically show a nonspecific mixed infiltrate, but established lesions may reveal granulomatous formation and neutrophilic microabscesses.^1,2 Asteroid bodies, which are cigar-shaped yeasts surrounded by eosinophilic coronae radiata, may be found. Organisms are sparsely distributed within the lesions, necessitating a thorough examination of the culture for identification.

Clinical Features

Sporotrichosis has 3 main classifications: lymphocutaneous, fixed cutaneous, and disseminated. Lymphocutaneous sporotrichosis is the most common form of the infection.² The disease presents with a small indurated papule occurring approximately 7 to 30 days after inoculation into the skin. The papule slowly enlarges, forms a nodule, and then frequently ulcerates. Over time, draining lymphatics become edematous and inflammatory, and a chain of secondary nodules begins to appear proximal to the initial lesion. The primary and secondary nodules may continue to ulcerate; alternately, they may heal or become chronic.

In fixed cutaneous sporotrichosis, the infection remains localized to one region and a granuloma may develop, which also may ulcerate. Satellite nodules may appear along the periphery of the lesion. Lymphatic spread is not observed in this form of 
the disease.

The disseminated form is a result of hematogenous spread from the primary inoculation site and typically occurs in an immunocompromised host. This form can present as pulmonary disease, sinusitis, and meningitis.¹

Differential Diagnosis

The differential diagnosis for sporotrichosis includes atypical mycobacteria, nocardiosis, blastomycosis, pyogenic bacteria, leishmaniasis, tularemia, 
and tuberculosis.

Treatment

Treatment of sporotrichosis is always required. A saturated solution of potassium iodide has classically been used; however, it is frequently associated with side effects and can be problematic to administer.¹² Given its low cost and traditional efficacy, it may still be used in some parts of the world.

Currently, the treatment of choice for fixed cutaneous and lymphocutaneous sporotrichosis is itraconazole 100 to 200 mg once daily for 3 to 6 months.¹ The recommended treatment of osteoarticular sporotrichosis is itraconazole, but prolonged therapy is required.

Heat therapy is an alternative treatment option, as certain strains of S schenckii do not grow at temperatures higher than 35°C. Hot compresses must be used for at least 1 hour a day for several months, which may affect patient compliance.

Immunocompromised patients often have disseminated infection and require lifelong suppressive therapy with itraconazole and may require initial treatment with amphotericin B.¹³

Conclusion

Subcutaneous sporotrichosis can develop in patients with a traumatic injury involving vegetation, soil, or animals. Although some patients may develop more invasive disease, most infections in immunocompetent patients will resolve after 3 to 6 months of itraconazole 100 to 200 mg once daily.¹

The Diagnosis: Amelanotic Melanoma In Situ

Histopathology revealed a broad asymmetric melanocytic proliferation at the dermoepidermal junction, consisting both of singly dispersed cells as well as randomly positioned nests (Figure 1). The single cells demonstrated junctional confluence and extension along adnexal structures highlighted by melan-A stain 
(Figure 2). The melanocytes were markedly atypical with enlarged and hyperchromatic nuclei containing multiple nucleoli. No dermal involvement was seen. There was papillary dermal fibrosis and an active host lymphocytic response. Based on these findings, a diagnosis of amelanotic melanoma in situ was made.

Figure 1. Histopathology revealed confluence of atypical melanocytes at the dermoepidermal junction and pagetoid scatter of melanocytes to the spinous layer (A)(H&E, original magnification ×4). Higher-power magnification highlighted the atypia of the individual melanocytes (B)(H&E, original magnification ×10).

Subsequent scouting punch biopsies at the superior, anterior, and posterior aspects of the lesion were performed (Figure 3). All 3 revealed a similar nested and single cell proliferation at the dermoepidermal junction, confirming residual amelanotic melanoma in situ. The patient was referred to the otolaryngology department and underwent wide local excision with 5-mm margins and reconstructive repair.

Amelanotic melanoma comprises 2% to 8% of cutaneous melanomas. It is more common in fair-skinned elderly women with an average age of diagnosis of 61.8 years. Because features typically associated with melanoma such as asymmetry, border irregularity, and color variegation often are absent, amelanotic melanoma represents a notable diagnostic challenge for clinicians. Lesions can present nonspecifically as erythematous macules, papules, patches, or plaques and can have associated pruritus and scale.^1,2

Clinical misdiagnoses for amelanotic melanoma include Bowen disease, basal cell carcinoma, actinic keratosis, lichenoid keratosis, intradermal nevus, dermatofibroma, inflamed seborrheic keratosis, nummular dermatitis, pyogenic granuloma, and granuloma annulare.^1-6 There have been few case reports of amelanotic melanoma in situ, with most being the lentigo maligna variant that were initially clinically diagnosed as superficial basal cell carcinoma, 
Bowen disease, or dermatitis.^7,8 In one case report, an amelanotic lentigo maligna was incidentally discovered after performing a mapping shave biopsy on what was normal-appearing skin.⁹

Dermoscopic evidence of vascular structures in lesions, including the presence of dotted vessels, milky red areas, and/or serpentine (linear irregular) vessels, may be the only clues to suggest amelanotic melanoma before biopsy. However, these findings are nonspecific and can be seen in other benign and malignant skin conditions.²

Complete surgical excision is the standard treatment of amelanotic melanoma in situ given its potential for invasion. However, the lack of pigment can make margins difficult to define. Because of its ability to detect disease beyond visual margins, Mohs micrographic surgery may have better cure rates than conventional excision.⁴ Prognosis for amelanotic melanoma is the same as other melanomas of equal thickness and location, though delay in diagnosis can adversely affect outcomes. Furthermore, amelanotic melanoma in situ can rapidly progress to invasive melanoma.^3,5 Thus it is important to maintain clinical suspicion for amelanotic melanoma in fair-skinned elderly women presenting with a persistent or recurring erythematous scaly lesion on sun-exposed skin.

The Diagnosis: Amelanotic Melanoma In Situ

Histopathology revealed a broad asymmetric melanocytic proliferation at the dermoepidermal junction, consisting both of singly dispersed cells as well as randomly positioned nests (Figure 1). The single cells demonstrated junctional confluence and extension along adnexal structures highlighted by melan-A stain 
(Figure 2). The melanocytes were markedly atypical with enlarged and hyperchromatic nuclei containing multiple nucleoli. No dermal involvement was seen. There was papillary dermal fibrosis and an active host lymphocytic response. Based on these findings, a diagnosis of amelanotic melanoma in situ was made.

Figure 1. Histopathology revealed confluence of atypical melanocytes at the dermoepidermal junction and pagetoid scatter of melanocytes to the spinous layer (A)(H&E, original magnification ×4). Higher-power magnification highlighted the atypia of the individual melanocytes (B)(H&E, original magnification ×10).

Subsequent scouting punch biopsies at the superior, anterior, and posterior aspects of the lesion were performed (Figure 3). All 3 revealed a similar nested and single cell proliferation at the dermoepidermal junction, confirming residual amelanotic melanoma in situ. The patient was referred to the otolaryngology department and underwent wide local excision with 5-mm margins and reconstructive repair.

Amelanotic melanoma comprises 2% to 8% of cutaneous melanomas. It is more common in fair-skinned elderly women with an average age of diagnosis of 61.8 years. Because features typically associated with melanoma such as asymmetry, border irregularity, and color variegation often are absent, amelanotic melanoma represents a notable diagnostic challenge for clinicians. Lesions can present nonspecifically as erythematous macules, papules, patches, or plaques and can have associated pruritus and scale.^1,2

Clinical misdiagnoses for amelanotic melanoma include Bowen disease, basal cell carcinoma, actinic keratosis, lichenoid keratosis, intradermal nevus, dermatofibroma, inflamed seborrheic keratosis, nummular dermatitis, pyogenic granuloma, and granuloma annulare.^1-6 There have been few case reports of amelanotic melanoma in situ, with most being the lentigo maligna variant that were initially clinically diagnosed as superficial basal cell carcinoma, 
Bowen disease, or dermatitis.^7,8 In one case report, an amelanotic lentigo maligna was incidentally discovered after performing a mapping shave biopsy on what was normal-appearing skin.⁹

Dermoscopic evidence of vascular structures in lesions, including the presence of dotted vessels, milky red areas, and/or serpentine (linear irregular) vessels, may be the only clues to suggest amelanotic melanoma before biopsy. However, these findings are nonspecific and can be seen in other benign and malignant skin conditions.²

Complete surgical excision is the standard treatment of amelanotic melanoma in situ given its potential for invasion. However, the lack of pigment can make margins difficult to define. Because of its ability to detect disease beyond visual margins, Mohs micrographic surgery may have better cure rates than conventional excision.⁴ Prognosis for amelanotic melanoma is the same as other melanomas of equal thickness and location, though delay in diagnosis can adversely affect outcomes. Furthermore, amelanotic melanoma in situ can rapidly progress to invasive melanoma.^3,5 Thus it is important to maintain clinical suspicion for amelanotic melanoma in fair-skinned elderly women presenting with a persistent or recurring erythematous scaly lesion on sun-exposed skin.

The Diagnosis: Amelanotic Melanoma In Situ

Histopathology revealed a broad asymmetric melanocytic proliferation at the dermoepidermal junction, consisting both of singly dispersed cells as well as randomly positioned nests (Figure 1). The single cells demonstrated junctional confluence and extension along adnexal structures highlighted by melan-A stain 
(Figure 2). The melanocytes were markedly atypical with enlarged and hyperchromatic nuclei containing multiple nucleoli. No dermal involvement was seen. There was papillary dermal fibrosis and an active host lymphocytic response. Based on these findings, a diagnosis of amelanotic melanoma in situ was made.

Figure 1. Histopathology revealed confluence of atypical melanocytes at the dermoepidermal junction and pagetoid scatter of melanocytes to the spinous layer (A)(H&E, original magnification ×4). Higher-power magnification highlighted the atypia of the individual melanocytes (B)(H&E, original magnification ×10).

Subsequent scouting punch biopsies at the superior, anterior, and posterior aspects of the lesion were performed (Figure 3). All 3 revealed a similar nested and single cell proliferation at the dermoepidermal junction, confirming residual amelanotic melanoma in situ. The patient was referred to the otolaryngology department and underwent wide local excision with 5-mm margins and reconstructive repair.

Amelanotic melanoma comprises 2% to 8% of cutaneous melanomas. It is more common in fair-skinned elderly women with an average age of diagnosis of 61.8 years. Because features typically associated with melanoma such as asymmetry, border irregularity, and color variegation often are absent, amelanotic melanoma represents a notable diagnostic challenge for clinicians. Lesions can present nonspecifically as erythematous macules, papules, patches, or plaques and can have associated pruritus and scale.^1,2

Clinical misdiagnoses for amelanotic melanoma include Bowen disease, basal cell carcinoma, actinic keratosis, lichenoid keratosis, intradermal nevus, dermatofibroma, inflamed seborrheic keratosis, nummular dermatitis, pyogenic granuloma, and granuloma annulare.^1-6 There have been few case reports of amelanotic melanoma in situ, with most being the lentigo maligna variant that were initially clinically diagnosed as superficial basal cell carcinoma, 
Bowen disease, or dermatitis.^7,8 In one case report, an amelanotic lentigo maligna was incidentally discovered after performing a mapping shave biopsy on what was normal-appearing skin.⁹

Dermoscopic evidence of vascular structures in lesions, including the presence of dotted vessels, milky red areas, and/or serpentine (linear irregular) vessels, may be the only clues to suggest amelanotic melanoma before biopsy. However, these findings are nonspecific and can be seen in other benign and malignant skin conditions.²

Complete surgical excision is the standard treatment of amelanotic melanoma in situ given its potential for invasion. However, the lack of pigment can make margins difficult to define. Because of its ability to detect disease beyond visual margins, Mohs micrographic surgery may have better cure rates than conventional excision.⁴ Prognosis for amelanotic melanoma is the same as other melanomas of equal thickness and location, though delay in diagnosis can adversely affect outcomes. Furthermore, amelanotic melanoma in situ can rapidly progress to invasive melanoma.^3,5 Thus it is important to maintain clinical suspicion for amelanotic melanoma in fair-skinned elderly women presenting with a persistent or recurring erythematous scaly lesion on sun-exposed skin.

The Diagnosis: Herpes Simplex Vegetans

Histopathologic examination using hematoxylin and eosin stain demonstrated marked pseudoepitheliomatous hyperplasia with granulation tissue, ulceration, and abundant exudate joined by a dense mixed inflammatory cell infiltrate that included a myriad of eosinophils (Figure, A). At higher power (Figure, B), many single and multinucleate acantholytic keratinocytes showed ground-glass nuclei and peripheral margination of chromatin within zones of ulceration and crust. Viral culture and direct fluorescent antibody assay identified herpes simplex virus (HSV) type 2. Based on the clinical and histopathologic findings, the patient was diagnosed with herpes simplex vegetans. He was initially treated with oral acyclovir and then oral famciclovir but showed minimal improvement. Eventually, he was referred to surgery and the mass was totally excised with clear margins and no evidence of underlying malignancy.

Histopathology revealed marked pseudoepitheliomatous hyperplasia, ulceration, and a dense mixed inflammatory cell infiltrate (A)(H&E, original magnification ×20). Many multinucleate acantholytic keratinocytes with ground-glass nuclei and peripheral margination of chromatin were shown (B)(H&E, original magnification ×400).

Herpes simplex virus is one of the most common sexually transmitted infections, with a notably increased incidence and prevalence among individuals with human immunodeficiency virus (HIV) infection.¹ Although typical HSV manifestation in immunocompetent patients includes clustered vesicles and/or ulcerations, immunocompromised patients may have unusual presentations, such as persistent and extensive ulcerations or nodular hyperkeratotic lesions.^2,3 Herpes vegetans, a term used to describe these atypical exophytic lesions, rarely has been reported in literature, but its presence should raise suspicion for possible underlying immunocompromise. The pathogenesis behind the hypertrophic nature of these lesions is not well understood, but it is postulated that the immune dysregulation from concomitant HIV and HSV infection plays a role.² Overproduction of tumor necrosis factor and IL-6 by HIV-infected dermal dendritic cells causes an increase in antiapoptotic factors within the epidermis, resulting in enhanced keratinocyte proliferation and clinical hyperkeratosis.^2,4

The differential diagnosis for herpes vegetans is somewhat broad, owing to the verrucous and often eroded appearance of the lesions. Biopsy and cultures can be obtained to differentiate from condyloma acuminatum, condyloma latum (secondary syphilis), pyoderma vegetans, pemphigus vegetans, granuloma inguinale, extraintestinal Crohn disease, deep fungal infections, cutaneous tuberculosis, and malignancy.^2-4 Histopathology shows epithelial hyperplasia and ulceration with scattered multinucleate keratinocytes, usually at the periphery of the ulcer, and intranuclear inclusions typical of HSV. In addition, a dense dermal infiltrate of lymphocytes, histiocytes, plasma cells, and eosinophils is usually present beneath the base of the ulcer.^2,4

Treatment options for herpes vegetans are limited due to the high prevalence of acyclovir-resistant (ACV-R) HSV-2 strains in HIV patients. Valacyclovir and penciclovir have been largely ineffective against ACV-R HSV due to their dependence on the same enzyme—thymidine kinase—involved in the mechanism of acyclovir resistance. Intravenous foscarnet and cidofovir have shown efficacy against ACV-R virus, but concerns of nephrotoxicity have limited their use over prolonged intervals.⁵ Castelo-Soccio et al⁶ reported promising results with intralesional cidofovir. This route of administration provides the advantage of increased bioavailability with reduced risk for nephrotoxicity.⁶ Finally, surgical resection may be considered for refractory lesions to circumvent the toxicity from systemically administered drugs.³

The Diagnosis: Herpes Simplex Vegetans

Histopathologic examination using hematoxylin and eosin stain demonstrated marked pseudoepitheliomatous hyperplasia with granulation tissue, ulceration, and abundant exudate joined by a dense mixed inflammatory cell infiltrate that included a myriad of eosinophils (Figure, A). At higher power (Figure, B), many single and multinucleate acantholytic keratinocytes showed ground-glass nuclei and peripheral margination of chromatin within zones of ulceration and crust. Viral culture and direct fluorescent antibody assay identified herpes simplex virus (HSV) type 2. Based on the clinical and histopathologic findings, the patient was diagnosed with herpes simplex vegetans. He was initially treated with oral acyclovir and then oral famciclovir but showed minimal improvement. Eventually, he was referred to surgery and the mass was totally excised with clear margins and no evidence of underlying malignancy.

Histopathology revealed marked pseudoepitheliomatous hyperplasia, ulceration, and a dense mixed inflammatory cell infiltrate (A)(H&E, original magnification ×20). Many multinucleate acantholytic keratinocytes with ground-glass nuclei and peripheral margination of chromatin were shown (B)(H&E, original magnification ×400).

Herpes simplex virus is one of the most common sexually transmitted infections, with a notably increased incidence and prevalence among individuals with human immunodeficiency virus (HIV) infection.¹ Although typical HSV manifestation in immunocompetent patients includes clustered vesicles and/or ulcerations, immunocompromised patients may have unusual presentations, such as persistent and extensive ulcerations or nodular hyperkeratotic lesions.^2,3 Herpes vegetans, a term used to describe these atypical exophytic lesions, rarely has been reported in literature, but its presence should raise suspicion for possible underlying immunocompromise. The pathogenesis behind the hypertrophic nature of these lesions is not well understood, but it is postulated that the immune dysregulation from concomitant HIV and HSV infection plays a role.² Overproduction of tumor necrosis factor and IL-6 by HIV-infected dermal dendritic cells causes an increase in antiapoptotic factors within the epidermis, resulting in enhanced keratinocyte proliferation and clinical hyperkeratosis.^2,4

The differential diagnosis for herpes vegetans is somewhat broad, owing to the verrucous and often eroded appearance of the lesions. Biopsy and cultures can be obtained to differentiate from condyloma acuminatum, condyloma latum (secondary syphilis), pyoderma vegetans, pemphigus vegetans, granuloma inguinale, extraintestinal Crohn disease, deep fungal infections, cutaneous tuberculosis, and malignancy.^2-4 Histopathology shows epithelial hyperplasia and ulceration with scattered multinucleate keratinocytes, usually at the periphery of the ulcer, and intranuclear inclusions typical of HSV. In addition, a dense dermal infiltrate of lymphocytes, histiocytes, plasma cells, and eosinophils is usually present beneath the base of the ulcer.^2,4

Treatment options for herpes vegetans are limited due to the high prevalence of acyclovir-resistant (ACV-R) HSV-2 strains in HIV patients. Valacyclovir and penciclovir have been largely ineffective against ACV-R HSV due to their dependence on the same enzyme—thymidine kinase—involved in the mechanism of acyclovir resistance. Intravenous foscarnet and cidofovir have shown efficacy against ACV-R virus, but concerns of nephrotoxicity have limited their use over prolonged intervals.⁵ Castelo-Soccio et al⁶ reported promising results with intralesional cidofovir. This route of administration provides the advantage of increased bioavailability with reduced risk for nephrotoxicity.⁶ Finally, surgical resection may be considered for refractory lesions to circumvent the toxicity from systemically administered drugs.³

The Diagnosis: Herpes Simplex Vegetans

Histopathologic examination using hematoxylin and eosin stain demonstrated marked pseudoepitheliomatous hyperplasia with granulation tissue, ulceration, and abundant exudate joined by a dense mixed inflammatory cell infiltrate that included a myriad of eosinophils (Figure, A). At higher power (Figure, B), many single and multinucleate acantholytic keratinocytes showed ground-glass nuclei and peripheral margination of chromatin within zones of ulceration and crust. Viral culture and direct fluorescent antibody assay identified herpes simplex virus (HSV) type 2. Based on the clinical and histopathologic findings, the patient was diagnosed with herpes simplex vegetans. He was initially treated with oral acyclovir and then oral famciclovir but showed minimal improvement. Eventually, he was referred to surgery and the mass was totally excised with clear margins and no evidence of underlying malignancy.

Histopathology revealed marked pseudoepitheliomatous hyperplasia, ulceration, and a dense mixed inflammatory cell infiltrate (A)(H&E, original magnification ×20). Many multinucleate acantholytic keratinocytes with ground-glass nuclei and peripheral margination of chromatin were shown (B)(H&E, original magnification ×400).

Herpes simplex virus is one of the most common sexually transmitted infections, with a notably increased incidence and prevalence among individuals with human immunodeficiency virus (HIV) infection.¹ Although typical HSV manifestation in immunocompetent patients includes clustered vesicles and/or ulcerations, immunocompromised patients may have unusual presentations, such as persistent and extensive ulcerations or nodular hyperkeratotic lesions.^2,3 Herpes vegetans, a term used to describe these atypical exophytic lesions, rarely has been reported in literature, but its presence should raise suspicion for possible underlying immunocompromise. The pathogenesis behind the hypertrophic nature of these lesions is not well understood, but it is postulated that the immune dysregulation from concomitant HIV and HSV infection plays a role.² Overproduction of tumor necrosis factor and IL-6 by HIV-infected dermal dendritic cells causes an increase in antiapoptotic factors within the epidermis, resulting in enhanced keratinocyte proliferation and clinical hyperkeratosis.^2,4

The differential diagnosis for herpes vegetans is somewhat broad, owing to the verrucous and often eroded appearance of the lesions. Biopsy and cultures can be obtained to differentiate from condyloma acuminatum, condyloma latum (secondary syphilis), pyoderma vegetans, pemphigus vegetans, granuloma inguinale, extraintestinal Crohn disease, deep fungal infections, cutaneous tuberculosis, and malignancy.^2-4 Histopathology shows epithelial hyperplasia and ulceration with scattered multinucleate keratinocytes, usually at the periphery of the ulcer, and intranuclear inclusions typical of HSV. In addition, a dense dermal infiltrate of lymphocytes, histiocytes, plasma cells, and eosinophils is usually present beneath the base of the ulcer.^2,4

Treatment options for herpes vegetans are limited due to the high prevalence of acyclovir-resistant (ACV-R) HSV-2 strains in HIV patients. Valacyclovir and penciclovir have been largely ineffective against ACV-R HSV due to their dependence on the same enzyme—thymidine kinase—involved in the mechanism of acyclovir resistance. Intravenous foscarnet and cidofovir have shown efficacy against ACV-R virus, but concerns of nephrotoxicity have limited their use over prolonged intervals.⁵ Castelo-Soccio et al⁶ reported promising results with intralesional cidofovir. This route of administration provides the advantage of increased bioavailability with reduced risk for nephrotoxicity.⁶ Finally, surgical resection may be considered for refractory lesions to circumvent the toxicity from systemically administered drugs.³

The Diagnosis: Idiopathic Guttate Hypomelanosis

A biopsy of the largest lesion from the left leg 
superior to the lateral malleolus was performed. 
 Histopathologic examination revealed solar elastosis, diminished number of focal melanocytes and pigment within keratinocytes compared to uninvolved skin, and presence of hyperkeratosis with flattening of rete ridges. The clinical presentation along with histopathologic analysis confirmed a diagnosis of idiopathic guttate hypomelanosis (IGH). The lesions were treated with short-exposure cryotherapy, which resulted in partial repigmentation after several treatments.

Idiopathic guttate hypomelanosis is a common but underreported condition in elderly patients that usually presents with small, discrete, asymptomatic, hypopigmented macules. The frequency of IGH increases with age.¹ Frequency of the condition is much lower in patients aged 21 to 30 years and does not exceed 7%. Lesions of IGH have a predilection for sun-exposed areas such as the arms and legs but rarely can be seen on the face and trunk. Facial lesions of IGH are more frequently reported in women.¹ The size of lesions can be up to 1.5 cm in diameter. The condition generally is self-limited, but some patients may express aesthetic concerns. Rare cases of IGH in children have been associated with prolonged sun exposure.²

The etiology of IGH is unknown but an association with sun exposure has been noted. Patients with IGH frequently show other signs of photoaging, such as numerous seborrheic keratoses, solar lentigines, xeroses, freckles, and actinic keratoses.¹ Short-term exposure to UVB radiation and psoralen plus UVA therapy has been shown to cause IGH in patients with chronic diseases such as mycosis fungoides.^3-5 One small study that examined renal transplant recipients determined an association between HLA-DQ3 antigens and IGH, whereas HLA-DR8 antigens were not identified in any patients with IGH, indicating it may have some advantage in preventing the development of IGH.⁶ Shin et al¹ reported that IGH was prevalent among patients who regularly traumatized their skin by scrubbing.

Clinically, IGH should be differentiated from other conditions characterized by hypopigmentation, such as pityriasis alba, pityriasis versicolor, postinflammatory hypopigmentation, progressive macular hypomelanosis, and vitiligo. Aside from clinical examination, histopathologic studies are helpful in making a definitive diagnosis. The differential diagnosis of IGH is presented in the Table.

Histopathology of IGH lesions usually reveals slight atrophy of the epidermis with flattening of rete ridges and concomitant hyperkeratosis. A thickened stratum granulosum also has been noted in lesions of IGH.² The diminished number of melanocytes and melanin pigment granules along with hyperkeratosis both appear to contribute to the hypopigmentation noted in IGH.⁷ Ultrastructural studies of lesions of IGH can confirm melanocytic degeneration and a decreased number of melanosomes in melanocytes and keratinocytes.^2,8

There is no uniformly effective treatment of IGH. Topical application of tacrolimus and tretinoin have shown efficacy in repigmenting IGH lesions.^8,9 Short-exposure cryotherapy with a duration of 3 to 
5 seconds, localized chemical peels, and/or local dermabrasion can be helpful.^10-12 CO₂ lasers also have demonstrated promising results.¹³

The Diagnosis: Idiopathic Guttate Hypomelanosis

A biopsy of the largest lesion from the left leg 
superior to the lateral malleolus was performed. 
 Histopathologic examination revealed solar elastosis, diminished number of focal melanocytes and pigment within keratinocytes compared to uninvolved skin, and presence of hyperkeratosis with flattening of rete ridges. The clinical presentation along with histopathologic analysis confirmed a diagnosis of idiopathic guttate hypomelanosis (IGH). The lesions were treated with short-exposure cryotherapy, which resulted in partial repigmentation after several treatments.

Idiopathic guttate hypomelanosis is a common but underreported condition in elderly patients that usually presents with small, discrete, asymptomatic, hypopigmented macules. The frequency of IGH increases with age.¹ Frequency of the condition is much lower in patients aged 21 to 30 years and does not exceed 7%. Lesions of IGH have a predilection for sun-exposed areas such as the arms and legs but rarely can be seen on the face and trunk. Facial lesions of IGH are more frequently reported in women.¹ The size of lesions can be up to 1.5 cm in diameter. The condition generally is self-limited, but some patients may express aesthetic concerns. Rare cases of IGH in children have been associated with prolonged sun exposure.²

The etiology of IGH is unknown but an association with sun exposure has been noted. Patients with IGH frequently show other signs of photoaging, such as numerous seborrheic keratoses, solar lentigines, xeroses, freckles, and actinic keratoses.¹ Short-term exposure to UVB radiation and psoralen plus UVA therapy has been shown to cause IGH in patients with chronic diseases such as mycosis fungoides.^3-5 One small study that examined renal transplant recipients determined an association between HLA-DQ3 antigens and IGH, whereas HLA-DR8 antigens were not identified in any patients with IGH, indicating it may have some advantage in preventing the development of IGH.⁶ Shin et al¹ reported that IGH was prevalent among patients who regularly traumatized their skin by scrubbing.

Clinically, IGH should be differentiated from other conditions characterized by hypopigmentation, such as pityriasis alba, pityriasis versicolor, postinflammatory hypopigmentation, progressive macular hypomelanosis, and vitiligo. Aside from clinical examination, histopathologic studies are helpful in making a definitive diagnosis. The differential diagnosis of IGH is presented in the Table.

Histopathology of IGH lesions usually reveals slight atrophy of the epidermis with flattening of rete ridges and concomitant hyperkeratosis. A thickened stratum granulosum also has been noted in lesions of IGH.² The diminished number of melanocytes and melanin pigment granules along with hyperkeratosis both appear to contribute to the hypopigmentation noted in IGH.⁷ Ultrastructural studies of lesions of IGH can confirm melanocytic degeneration and a decreased number of melanosomes in melanocytes and keratinocytes.^2,8

There is no uniformly effective treatment of IGH. Topical application of tacrolimus and tretinoin have shown efficacy in repigmenting IGH lesions.^8,9 Short-exposure cryotherapy with a duration of 3 to 
5 seconds, localized chemical peels, and/or local dermabrasion can be helpful.^10-12 CO₂ lasers also have demonstrated promising results.¹³

The Diagnosis: Idiopathic Guttate Hypomelanosis

A biopsy of the largest lesion from the left leg 
superior to the lateral malleolus was performed. 
 Histopathologic examination revealed solar elastosis, diminished number of focal melanocytes and pigment within keratinocytes compared to uninvolved skin, and presence of hyperkeratosis with flattening of rete ridges. The clinical presentation along with histopathologic analysis confirmed a diagnosis of idiopathic guttate hypomelanosis (IGH). The lesions were treated with short-exposure cryotherapy, which resulted in partial repigmentation after several treatments.

Idiopathic guttate hypomelanosis is a common but underreported condition in elderly patients that usually presents with small, discrete, asymptomatic, hypopigmented macules. The frequency of IGH increases with age.¹ Frequency of the condition is much lower in patients aged 21 to 30 years and does not exceed 7%. Lesions of IGH have a predilection for sun-exposed areas such as the arms and legs but rarely can be seen on the face and trunk. Facial lesions of IGH are more frequently reported in women.¹ The size of lesions can be up to 1.5 cm in diameter. The condition generally is self-limited, but some patients may express aesthetic concerns. Rare cases of IGH in children have been associated with prolonged sun exposure.²

The etiology of IGH is unknown but an association with sun exposure has been noted. Patients with IGH frequently show other signs of photoaging, such as numerous seborrheic keratoses, solar lentigines, xeroses, freckles, and actinic keratoses.¹ Short-term exposure to UVB radiation and psoralen plus UVA therapy has been shown to cause IGH in patients with chronic diseases such as mycosis fungoides.^3-5 One small study that examined renal transplant recipients determined an association between HLA-DQ3 antigens and IGH, whereas HLA-DR8 antigens were not identified in any patients with IGH, indicating it may have some advantage in preventing the development of IGH.⁶ Shin et al¹ reported that IGH was prevalent among patients who regularly traumatized their skin by scrubbing.

Clinically, IGH should be differentiated from other conditions characterized by hypopigmentation, such as pityriasis alba, pityriasis versicolor, postinflammatory hypopigmentation, progressive macular hypomelanosis, and vitiligo. Aside from clinical examination, histopathologic studies are helpful in making a definitive diagnosis. The differential diagnosis of IGH is presented in the Table.

Histopathology of IGH lesions usually reveals slight atrophy of the epidermis with flattening of rete ridges and concomitant hyperkeratosis. A thickened stratum granulosum also has been noted in lesions of IGH.² The diminished number of melanocytes and melanin pigment granules along with hyperkeratosis both appear to contribute to the hypopigmentation noted in IGH.⁷ Ultrastructural studies of lesions of IGH can confirm melanocytic degeneration and a decreased number of melanosomes in melanocytes and keratinocytes.^2,8

There is no uniformly effective treatment of IGH. Topical application of tacrolimus and tretinoin have shown efficacy in repigmenting IGH lesions.^8,9 Short-exposure cryotherapy with a duration of 3 to 
5 seconds, localized chemical peels, and/or local dermabrasion can be helpful.^10-12 CO₂ lasers also have demonstrated promising results.¹³

The Diagnosis: Allergic Contact Dermatitis to 
Para-phenylenediamine

To darken the color of henna and increase penetrance and staining, para-phenylenediamine (PPD) is added.¹ Allergic contact dermatitis is the most common type of hypersensitivity to PPD.² A retrospective study that examined severe adverse events from applying henna dyes in children found that angioedema of mucosal tissues was the most common severe adverse event; others included renal failure and shock.³

Black henna is associated with multiple cultural practices. For example, Indian weddings contain a henna decoration ceremony for the bride based on the belief that the longer the henna lasts, the longer the marriage lasts. Black henna is favored for this practice, as it lasts longer than red henna.

Henna (Lawsonia inermis) is a plant that contains the molecule lawsone (naphthoquinone). Lawsone has an intense affinity for keratin; as a result, lawsone is frequently added to temporary body tattoos and hair dyes to create a relatively permanent change in skin or hair color.⁴ Henna is mixed with hennotannic acid to release the lawsone from the plant. Lawsone and hennotannic acid rarely cause allergic reactions.^1,5-7 Once applied to skin, henna takes a few hours to dry, and the resulting color is orange to red.⁸ Often, PPD is added to henna paste to create a black color, to speed up the drying process, and to increase its longevity.

Para-phenylenediamine has been repeatedly reported to cause allergic contact dermatitis. We describe a case of allergic contact dermatitis secondary to PPD in black henna. Our patient is a clear example that PPD is the allergen in black henna given that there was no reaction to the natural red henna tattoo that was applied at the same time to the palmar surfaces of the hands (Figure). Aside from the bullous reaction to black henna dye described here, other reported presentations include erythema multiforme–like and exudative erythema reactions.^9,10

Contact dermatitis lesions from black henna dye can be treated with topical corticosteroids. Patients may develop residual postinflammatory hyperpigmentation or hypopigmentation, leukoderma, keloids, or scars.^1,11,12

The Diagnosis: Allergic Contact Dermatitis to 
Para-phenylenediamine

To darken the color of henna and increase penetrance and staining, para-phenylenediamine (PPD) is added.¹ Allergic contact dermatitis is the most common type of hypersensitivity to PPD.² A retrospective study that examined severe adverse events from applying henna dyes in children found that angioedema of mucosal tissues was the most common severe adverse event; others included renal failure and shock.³

Black henna is associated with multiple cultural practices. For example, Indian weddings contain a henna decoration ceremony for the bride based on the belief that the longer the henna lasts, the longer the marriage lasts. Black henna is favored for this practice, as it lasts longer than red henna.

Henna (Lawsonia inermis) is a plant that contains the molecule lawsone (naphthoquinone). Lawsone has an intense affinity for keratin; as a result, lawsone is frequently added to temporary body tattoos and hair dyes to create a relatively permanent change in skin or hair color.⁴ Henna is mixed with hennotannic acid to release the lawsone from the plant. Lawsone and hennotannic acid rarely cause allergic reactions.^1,5-7 Once applied to skin, henna takes a few hours to dry, and the resulting color is orange to red.⁸ Often, PPD is added to henna paste to create a black color, to speed up the drying process, and to increase its longevity.

Para-phenylenediamine has been repeatedly reported to cause allergic contact dermatitis. We describe a case of allergic contact dermatitis secondary to PPD in black henna. Our patient is a clear example that PPD is the allergen in black henna given that there was no reaction to the natural red henna tattoo that was applied at the same time to the palmar surfaces of the hands (Figure). Aside from the bullous reaction to black henna dye described here, other reported presentations include erythema multiforme–like and exudative erythema reactions.^9,10

Contact dermatitis lesions from black henna dye can be treated with topical corticosteroids. Patients may develop residual postinflammatory hyperpigmentation or hypopigmentation, leukoderma, keloids, or scars.^1,11,12

The Diagnosis: Allergic Contact Dermatitis to 
Para-phenylenediamine

To darken the color of henna and increase penetrance and staining, para-phenylenediamine (PPD) is added.¹ Allergic contact dermatitis is the most common type of hypersensitivity to PPD.² A retrospective study that examined severe adverse events from applying henna dyes in children found that angioedema of mucosal tissues was the most common severe adverse event; others included renal failure and shock.³

Black henna is associated with multiple cultural practices. For example, Indian weddings contain a henna decoration ceremony for the bride based on the belief that the longer the henna lasts, the longer the marriage lasts. Black henna is favored for this practice, as it lasts longer than red henna.

Henna (Lawsonia inermis) is a plant that contains the molecule lawsone (naphthoquinone). Lawsone has an intense affinity for keratin; as a result, lawsone is frequently added to temporary body tattoos and hair dyes to create a relatively permanent change in skin or hair color.⁴ Henna is mixed with hennotannic acid to release the lawsone from the plant. Lawsone and hennotannic acid rarely cause allergic reactions.^1,5-7 Once applied to skin, henna takes a few hours to dry, and the resulting color is orange to red.⁸ Often, PPD is added to henna paste to create a black color, to speed up the drying process, and to increase its longevity.

Para-phenylenediamine has been repeatedly reported to cause allergic contact dermatitis. We describe a case of allergic contact dermatitis secondary to PPD in black henna. Our patient is a clear example that PPD is the allergen in black henna given that there was no reaction to the natural red henna tattoo that was applied at the same time to the palmar surfaces of the hands (Figure). Aside from the bullous reaction to black henna dye described here, other reported presentations include erythema multiforme–like and exudative erythema reactions.^9,10

Contact dermatitis lesions from black henna dye can be treated with topical corticosteroids. Patients may develop residual postinflammatory hyperpigmentation or hypopigmentation, leukoderma, keloids, or scars.^1,11,12