Essential Thrombocythemia : Clinical and Blood Coagulation Studies in Twenty Patients

Essential thrombocythemia (ET) is a myeloproliferative disorder, characterized by megakaryocytic hyperplasia in the bone marrow and persistent thrombocytosis without polycythemia vera, chronic myelogenous leukemia or idiopathic myelofibrosis. Though ET has been considerd to be a rare disease in Japan, we have experienced 20 cases in the last twelve years (1978～1990). The patients were 7 males and 13 females ranging in age from 28 to 91 years with a median age of 59. The platelet count ranged from 824～2773×10^9/l (mean 1484×10^9/l). Spontaneous platelet aggregation (SPA) was noted in 14 patients who had some clinical symptoms. Five SPA-negative patients were asymptomatic and demonstrated thrombocytosis during their medical examimations. As regarding therapy of essential thrombocythemia, active therapy by alkylating and antiplatelet drugs should be undertaken in SPA-positive patients, whereas SPA-negative patients have only to be administered with antiplatelet drugs.