The one-nail brown band: macro- and micro-morphology.

The nail matrix contains melanocytes in the epidermal basal layer, but pigment is not visible in the gross anatomy of the nail plate in Caucasians. Hyperpigmentation due to an increase in melanogenesis, and subsequently melanin pigment, in the nail may be induced by certain drugs, tumours or endocrinological diseases (1-5). The whole nail may be affected, whilst some drugs or tumours produce longitudinal or vertical bands (3). Importantly, longitudinal pigmented bands are a normal finding in subjects of darker pigmented races (6). We wish to report a case of benign melanonychia striata due to chemotherapy that was confirmed by histological examination.