Nail pigmentation caused by hydroxyurea: report of 9 cases.

We report a series of 9 patients, 6 men and 3 women, who presented nail hyperpigmentation arising between 6 and 24 months from the start of hydroxyurea therapy. The most commonly observed clinical pattern was that of longitudinal melanonychia. In only 1 patient, who was affected in all 20 nails, we observed longitudinal melanonychia, diffuse melanonychia, and hyperpigmentation of the skin.