Thrombocytopenia is common in patients with paroxysmal nocturnal hemoglobinuria (PNH) and is often severe enough to cause death. We describe a patient with paroxysmal nocturnal hemoglobinuria and severe thrombocytopenia in whom the latter condition was successfully treated with vincristine.

A 51-year-old man was referred to us in March 1982 because of nocturnal hemoglobinuria and general fatigue. Lactate dehydrogenase levels were 1844 IU/L (isozymes I and II dominant pattern); the erythrocyte count was 3.91 million cells/µL; the hemoglobin level was 8.6 g/dL; the platelet count was 40 000 cells/µL; and the leukocyte count was 7600 cells/µL, with normal differentials. The serum acetylcholinesterase level was decreased to 0.5 U (normal range, 1.8 to 2.2 U), and results of Ham and sucrose-water tests were positive. The patient's condition was diagnosed as PNH. Administration of prednisolone (60 mg/d) and mepitiostane (45 mg/d) was effective. The patient was followed without any medication until March 1994, when purpura and mucosal bleeding appeared. His platelet count was 3000 cells/µL, but coagulation profiles were normal. CD59 was decreased on the cell surface of erythrocytes and granulocytes [1]. The PIG-A gene [2] of bone marrow cells was found to be nonfunctional. Vincristine, 1.2 mg, was intravenously administered weekly beginning on 3 May 1992 after informed consent was obtained. The patient's platelet count increased to 111 000 cells/µL by 21 May. Reticulocytes also increased from 1.4% to 7%, and the patient's hemoglobin level gradually returned to normal. Vincristine therapy was discontinued after 7 doses on 21 July, and platelet counts remained normal without maintenance therapy for more than 14 months.

Vinca alkaloids often increase platelet counts in patients with immune thrombocytopenic purpura or thrombotic thrombocytopenic purpura [3, 4]. Because an autoimmune process has been reported as a cause of thrombocytopenia in patients with PNH [5], it may explain the effectiveness of vincristine. Vincristine seems worthwhile for the treatment of severe thrombocytopenia in PNH, given that no effective treatment exists for this disorder.