Fungal Leukonychia and Melanonychia: a Review

Fungal leukonychia is a common condition in immunosuppressed patients; the most common clinical forms are white superficial and proximal white superficial onychomycosis. It is frequently associated with Trichophyton mentagrophytes var. interdigitale and with Trichophyton rubrum. The diagnosis can be easily made by direct examination and culture. Fungal melanonychia is the nail plate pigmentation caused by fungal infections. The most frequently isolated fungi is T. rubrum and melanized molds like Neoscytalidium dimidiatum. The main differential diagnosis is malignant melanoma, although other causes include subungueal hematomas, exogenous pigmentation, and bacterial infection. If homogeneous pigmentation in lines or structureless discoloration, and the absence of melanin inclusions are seen by dermoscopy, diagnosis must be complemented with KOH preparations and cultures.