Hyperpigmented forearms and nail: a quiz.

A 75-year-old woman with a history of hydroxychloroquinetreated cutaneous lupus erythematosus presented with a bilateral sharply demarcated macular hyperpigmentation on both forearms (Fig. 1) and a partial melanonychia of the right thumb nail. This pigmentation disorder developed gradually over a 6-month period. No retinal pigmentation and no systemic disorder were revealed. Dermoscopy of the nail plate and nail bed showed pigment deposition. Histological examination of a skin biopsy showed basal hyperpigmentation of the epidermis and a diffuse deposition of hemosiderin and melanin in the dermis. Abundant hemosiderin deposits were clearly indicated by iron staining (Fig. 2).