Hydroxyurea (HU) has been used in patients with essential thrombocythemia (ET) to reduce the frequency and severity of thrombotic complications of the disease. It acts by causing bone marrow depression, resulting in a decrease in platelet and leukocyte counts and in anemia with megaloblastosis. Herein we report a case of an 80-year-old man with ET who developed severe hemolytic anemia requiring multiple packed RBC transfusions while being treated with HU. The hemolysis persisted until discontinuation of the drug. This case suggests hemolysis as a potential side effect of HU and raises the clinical concern that not all HU-induced anemia is secondary to erythropoiesis depression. With the increasing use of HU in the management of ET, hemoglobinopathy, and other diseases, the importance of monitoring for hemolysis must be further emphasized in these patients.
2004 Wiley-Liss, Inc.