Melanonychia due to hydroxyurea therapy

Hydroxyurea (HU) is a cytostatic agent which is widely used in the treatment of myeloproliferative disorders, in particular chronic myeloid leukemia. HU inhibits DNA synthesis through its action on ribonucleoside diphosphate-reductase, which catalyses the reduction of ribonucleotides. Its antitumor effect mainly consists of a decrease in white blood cell count, an increase in hemoglobin to normal values, a decrease of thrombocytosis and a reduction of splenomegaly. Long-term HU therapy causes hematologic side effects, including marrow suppression and megaloblastosis. Cutaneous adverse reactions are frequently described, and consist mainly of atrophy of the skin, leg ulcers, erythema of the face and hands, alopecia, hyperpigmentation of the skin and nail abnormalities. A 77-year-old woman with chronic myeloid leukemia was treated with oral HU (2 g/day) for 15 months. She complained of an ulcer of the left malleolar area, but the physical examination was also remarkable for diffuse and longitudinal nail hyperpigmentation of all the nails of both hands and feet. A diagnosis of HU-induced ulcer and melanonychia was made and HU was discontinued. The patient started a therapy with oral imatinib mesylate (400 mg/day) and oral pentoxifylline (400 mg/day). Two months later, the leg ulcer resolved and the hyperpigmented bands on the fingernails were lighter.