Julia R. Nunley, MD

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

Case Report

A 41-year-old man with no dermatologic history presented for a skin examination. During a full-body skin examination, a lesion was identified on the right third toe that was partially visible underneath the nail plate. The patient stated that the lesion had been present for many years and did not appear to be growing but did cause occasional pain. On examination a 1-cm verrucous, hyperkeratotic, tan papule was noted at the distal end of the nail bed causing partial onycholysis (Figure 1). It was not tender to palpation.

A shave biopsy was obtained of the visible portion of the lesion, which revealed hyperkeratosis, acanthosis, and a population of dermal spindle cells in a myxoid stroma that could not be definitively identified. Special stains were nondiagnostic. The patient was referred to dermatologic surgery for rebiopsy of the lesion after removal of the nail plate. Mature bone was seen embedded in the dermis (Figure 2), and a diagnosis of subungual exostosis was made. Radiography of the digit confirmed a bony excrescence from the tuft of the toe, and the patient was referred to orthopedic surgery for definitive excision. There was no evidence of recurrence at 1-year follow-up.

Comment

Subungual exostosis is an uncommon benign bone tumor located beneath or adjacent to the nail bed on the dorsal aspect of the distal phalanx.¹ Although it can occur on any digit, 70% to 80% of cases have arisen on the distal phalanx of the hallux.² Both sexes are equally susceptible. The majority of lesions occur during the second or third decades of life and usually are asymptomatic unless there is trauma or infection. Growth of the lesion over time can cause lifting or deformity of the nail plate and can cause slight discomfort while walking if located on the great toe.³ Common differential diagnoses include osteochondroma, wart, fibroma, paronychia, myositis ossificans, and pyogenic granuloma.^3,4 Diagnosis can be confirmed with radiography, which should be performed prior to any biopsy or invasive procedure. In our patient, initial radiography could have obviated the need for 2 biopsies prior to definitive excision. Histopathologic evaluation typically reveals mature trabecular bone (Figure 2) surrounded by a fibrocartilage cap.

Subungual exostosis begins as an area of proliferating fibrous tissue with cartilaginous metaplasia located beneath or adjacent to the nail bed on the dorsal aspect of the distal phalanx.¹ This cartilage undergoes enchondral ossification and is converted to trabecular bone. As the lesion grows and matures, the cartilaginous cap blends imperceptibly with the nail bed and comes into continuity with the underlying distal phalanx.^1,3 This process continues until the lesion fuses completely with the distal phalanx.¹ Although the cause of subungual exostosis has not been clearly established, chronic irritation, trauma, and chronic infections are considered causative factors of fibrocartilaginous metaplasia.⁴

Conclusion

Subungual exostosis is a benign bony tumor of the distal phalanx that can cause pain and onycholysis. Radiography of the affected digit is a noninvasive way to confirm the diagnosis and should be part of the initial workup of any suspicious subungual tumor. Once identified, complete removal of the exostosis by excision has been shown to be an effective treatment with few complications.

Case Report

A 41-year-old man with no dermatologic history presented for a skin examination. During a full-body skin examination, a lesion was identified on the right third toe that was partially visible underneath the nail plate. The patient stated that the lesion had been present for many years and did not appear to be growing but did cause occasional pain. On examination a 1-cm verrucous, hyperkeratotic, tan papule was noted at the distal end of the nail bed causing partial onycholysis (Figure 1). It was not tender to palpation.

A shave biopsy was obtained of the visible portion of the lesion, which revealed hyperkeratosis, acanthosis, and a population of dermal spindle cells in a myxoid stroma that could not be definitively identified. Special stains were nondiagnostic. The patient was referred to dermatologic surgery for rebiopsy of the lesion after removal of the nail plate. Mature bone was seen embedded in the dermis (Figure 2), and a diagnosis of subungual exostosis was made. Radiography of the digit confirmed a bony excrescence from the tuft of the toe, and the patient was referred to orthopedic surgery for definitive excision. There was no evidence of recurrence at 1-year follow-up.

Comment

Subungual exostosis is an uncommon benign bone tumor located beneath or adjacent to the nail bed on the dorsal aspect of the distal phalanx.¹ Although it can occur on any digit, 70% to 80% of cases have arisen on the distal phalanx of the hallux.² Both sexes are equally susceptible. The majority of lesions occur during the second or third decades of life and usually are asymptomatic unless there is trauma or infection. Growth of the lesion over time can cause lifting or deformity of the nail plate and can cause slight discomfort while walking if located on the great toe.³ Common differential diagnoses include osteochondroma, wart, fibroma, paronychia, myositis ossificans, and pyogenic granuloma.^3,4 Diagnosis can be confirmed with radiography, which should be performed prior to any biopsy or invasive procedure. In our patient, initial radiography could have obviated the need for 2 biopsies prior to definitive excision. Histopathologic evaluation typically reveals mature trabecular bone (Figure 2) surrounded by a fibrocartilage cap.

Subungual exostosis begins as an area of proliferating fibrous tissue with cartilaginous metaplasia located beneath or adjacent to the nail bed on the dorsal aspect of the distal phalanx.¹ This cartilage undergoes enchondral ossification and is converted to trabecular bone. As the lesion grows and matures, the cartilaginous cap blends imperceptibly with the nail bed and comes into continuity with the underlying distal phalanx.^1,3 This process continues until the lesion fuses completely with the distal phalanx.¹ Although the cause of subungual exostosis has not been clearly established, chronic irritation, trauma, and chronic infections are considered causative factors of fibrocartilaginous metaplasia.⁴

Conclusion

Subungual exostosis is a benign bony tumor of the distal phalanx that can cause pain and onycholysis. Radiography of the affected digit is a noninvasive way to confirm the diagnosis and should be part of the initial workup of any suspicious subungual tumor. Once identified, complete removal of the exostosis by excision has been shown to be an effective treatment with few complications.

Case Report

A 41-year-old man with no dermatologic history presented for a skin examination. During a full-body skin examination, a lesion was identified on the right third toe that was partially visible underneath the nail plate. The patient stated that the lesion had been present for many years and did not appear to be growing but did cause occasional pain. On examination a 1-cm verrucous, hyperkeratotic, tan papule was noted at the distal end of the nail bed causing partial onycholysis (Figure 1). It was not tender to palpation.

A shave biopsy was obtained of the visible portion of the lesion, which revealed hyperkeratosis, acanthosis, and a population of dermal spindle cells in a myxoid stroma that could not be definitively identified. Special stains were nondiagnostic. The patient was referred to dermatologic surgery for rebiopsy of the lesion after removal of the nail plate. Mature bone was seen embedded in the dermis (Figure 2), and a diagnosis of subungual exostosis was made. Radiography of the digit confirmed a bony excrescence from the tuft of the toe, and the patient was referred to orthopedic surgery for definitive excision. There was no evidence of recurrence at 1-year follow-up.

Comment

Subungual exostosis is an uncommon benign bone tumor located beneath or adjacent to the nail bed on the dorsal aspect of the distal phalanx.¹ Although it can occur on any digit, 70% to 80% of cases have arisen on the distal phalanx of the hallux.² Both sexes are equally susceptible. The majority of lesions occur during the second or third decades of life and usually are asymptomatic unless there is trauma or infection. Growth of the lesion over time can cause lifting or deformity of the nail plate and can cause slight discomfort while walking if located on the great toe.³ Common differential diagnoses include osteochondroma, wart, fibroma, paronychia, myositis ossificans, and pyogenic granuloma.^3,4 Diagnosis can be confirmed with radiography, which should be performed prior to any biopsy or invasive procedure. In our patient, initial radiography could have obviated the need for 2 biopsies prior to definitive excision. Histopathologic evaluation typically reveals mature trabecular bone (Figure 2) surrounded by a fibrocartilage cap.

Subungual exostosis begins as an area of proliferating fibrous tissue with cartilaginous metaplasia located beneath or adjacent to the nail bed on the dorsal aspect of the distal phalanx.¹ This cartilage undergoes enchondral ossification and is converted to trabecular bone. As the lesion grows and matures, the cartilaginous cap blends imperceptibly with the nail bed and comes into continuity with the underlying distal phalanx.^1,3 This process continues until the lesion fuses completely with the distal phalanx.¹ Although the cause of subungual exostosis has not been clearly established, chronic irritation, trauma, and chronic infections are considered causative factors of fibrocartilaginous metaplasia.⁴

Conclusion

Subungual exostosis is a benign bony tumor of the distal phalanx that can cause pain and onycholysis. Radiography of the affected digit is a noninvasive way to confirm the diagnosis and should be part of the initial workup of any suspicious subungual tumor. Once identified, complete removal of the exostosis by excision has been shown to be an effective treatment with few complications.