Frictional longitudinal melanonychia: a new entity.

Longitudinal melanonychia of the toes initiated by repeated trauma from the footwear is described as a new entity in a clinical study of 12 patients. Its proper recognition should help to rule out the brown streaks due to malignant melanoma. The nail pigmentation appears over the distal bony phalanx where the deep matrix covered by the proximal nail fold is exposed to friction or pressure of the narrowing portion of the tip of the shoe. Histological studies revealed hyperplasia of the matrix, some melanin granules in the upper dermis with increased pigmentation of the basal cell layer of the epithelium, and marked melanotic pigment in the nail plate.