Abstract

Acanthosis nigricans (AN) is a velvety darkening and thickening of the skin, typically in intertriginous areas. It is often associated with underlying conditions, notably insulin resistance and diabetes mellitus. Microscopically it is characterized by epidermal papillomatosis, hyperkeratosis and variable but usually inconspicuous pigmentation. Exceptionally, AN may occur “ectopically” in donor-skin of intertriginous origin used as grafts at distant sites. We describe the case of a 10-year-old boy with darkening of inguinal skin grafted to his hands for management of burn scar contracture. At one year of age the patient sustained deep partial and full-thickness burns to the ulnar and palmar aspects of both hands. Subsequent scar contractures were managed with excision and full-thickness skin grafts harvested from the inguinal crease. Physical examination revealed marked hyperpigmentation of the skin grafts which proved refractory to topical steroid and hydroquinone therapy. Recurrent contractures of the three ulnar digits and web creep of the third and fourth web spaces were evident bilaterally with ongoing hand growth. He underwent excision of the prior skin grafts, with advancement flap reconstruction, webspace deepening, and full thickness skin grafts from the ulnar forearm. On microscopy, the excised skin graft showed epidermal papillomatosis, hyperkeratosis, and mild basal pigmentation consistent with “ectopic AN.” The phenomenon of “ectopic AN” suggests a donor site-specific sensitivity of skin at certain sites to particular growth factors, and persistence of that property when the skin is transplanted to a different site.

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