Linear melanonychia due to subungual keratosis of the nail bed: a report of two cases

Longitudinal melanonychia displaying features of keratinized acanthoma is d escribed in two patients. In both cases, a pigmented band consisting of a s ubungual keratinized epithelial ridge originated in the nail bed. We have b een able to show, using the clinical and histological findings, that the or igin of the pigment is linked to its synthesis within the acanthoma of the nail bed. These lesions are reminiscent of pigmented seborrhoeic keratosis. The horny cysts are replaced, because of the special physiological longitu dinal arrangement of the ridges in the nail bed, by a single, prominent, lo ngitudinal, keratinized and pigmented mass.