Acquired Melanonychia in Chilean Patients with Essential Thrombocythemia Treated with Hydroxyurea: A Report of 7 Clinical Cases and Review of the Literature

Longitudinal melanonychia has been associated with a range of drugs, especially chemotherapeutic agents. We report 7 cases of melanonychia associated with the use of hydroxycarbamide for essential thrombocythemia. Of a patient population of 27, 7 (26%) developed melanonychia over a period of 2–7 years, and was not dose dependent. The high incidence of melanonychia in Chilean patients may be in part due to their Hispanic descent or to the high levels of UV radiation found in Santiago. 1. Introduction We present 7 cases, five men and two women, all with a diagnosis of essential thrombocythemia, who presented with longitudinal dark pigmentation of the nails after a period of 3 to 5 years of treatment with hydroxyurea. Acquired longitudinal melanonychia is characterized by the presence of longitudinal brown or black lines in the nail plate as a result of increased melanin deposits. They originate in the nail matrix and are the result of an increased production of melanin by matrix melanocytes or of an increased number of melanocytes in the nail matrix. 2. Patients Of 27 patients currently being followedup for essential thrombocythemia and being treated with hydroxycarbamide, 7 (26%) patients have developed melanonychia. The clinical details of the 7 patients are shown in Table 1, with a mean age of years, and all the patients were treated with hydroxyurea for essential thrombocythemia for a median time of 5 years (range 2–7 years) and a median dose of 1,500？gm/day (range 500–2500？mg/day). Table 1: Clinical features of nail pigmentation. All patients did not have significant comorbidities and the use of other drugs was limited to aspirin 100？mg and in four patients the use of allopurinol 100？mg/day. Nail examination (Figures 1(a) and 1(b)) showed a dark brown pigmentation distributed in well-defined longitudinal lines of varying width, and the nail was smooth and shiny. The lesions themselves were asymptomatic and Hutchinson’s sign was negative. With time, the lines occupied the full length of the nail. In two patients, there was a generalized hyperpigmentation of the skin. The number of nails affected was variable as was between nails of the hands and feet. There was no relation between the duration of hydroxycarbamide therapy or the dose used to control the essential thrombocythemia. Figure 1: (a) Close of longitudinal melanonychia. (b) Melanonychia of the thumb nail. 3. Controls (a)Seven patients (6 men and 1 woman) with polycythemia rubra vera and treated with venesection for a median of 5 years were evaluated for melanonychia, and none of the 7 patients