Fungal melanonychia.

Fungal melanonychia is a relatively rare nail disorder caused by nail infection that produces brown-to-black pigmentation of the nail unit. The number of organisms implicated as etiologic agents of fungal melanonychia is increasing, and the list currently tops 21 species of dematiaceous fungi and at least 8 species of nondematiaceous fungi. These superficial infections may clinically mimic subungual melanoma and are often not responsive to traditional antifungal therapy. This article reviews the literature on fungal melanonychia and the role of fungal melanin in infection.