Abstract

A 57-year-old Fitzpatrick type V female was evaluated in the Dermatology clinic for an asymptomatic monodactylous longitudinal melanonychia with focal distal onycholysis, splinter hemorrhages, and a small Hutchinson sign of the right index finger. She noticed these nail changes after removing polish from a manicure three weeks earlier. The clinical differential diagnosis included pigmented onychopapilloma, pigmented nail unit Bowen disease, and nail unit melanoma. A lateral longitudinal excision demonstrated broad regions of acantholysis and occasional dyskeratotic keratinocytes. Melan-A and MART-1 stains did not show a melanocytic proliferation. Fontana stained sections highlighted pigmentation in the epithelium. Subungual acantholytic dyskeratomas are rare, benign nail unit tumors first described in 2009; we report the first case of a pigmented variant. Various inciting agents including infection, immunologic factors, and trauma have been proposed and we hypothesize trauma from her recent manicure was the cause  in this patient.