[alpha-Interferon in the treatment of essential thrombocythemia].

Two patients with essential thrombocythemia were successfully treated by administering native alpha-interferon (alpha-IFN). One patient was a 38-year-old man in whom thrombocytosis was found accidentally. His platelet count on admission was 880,000/microliters and megakaryocytes increased. Three million units of alpha-IFN was administered subcutaneously everyday, and the platelet count decreased gradually to about 500,000/microliters within 2 weeks. The other patient was a 66-year-old woman who visited our hospital complaining of tenderness and swelling of the fingertips. Her platelet count was 1,610,000/microliters, and megakaryocytes increased and showed abnormal morphology. Six million units of alpha-IFN was administered subcutaneously every other day. The tenderness and swelling of the fingertips disappeared soon after the beginning of alpha-IFN administration. The platelet count decreased to about 500,000/microliters within 10 days, but she developed itching of the skin over the entire body. Therefore, alpha-IFN treatment was discontinued. It was suggested that alpha-IFN suppresses not only the maturation and proliferation of the progenitors of megakaryocytes but also the production of platelets from megakaryocytes. Administration of alpha-IFN should be considered in treating patients with essential thrombocythemia, because effects appear soon and alpha-IFN does not induce a second malignancy.