Primary Thrombocythemia in Japan: A Survey of 225 Patients.

Data on 225 Japanese patients with primary or essential thrombocythemia (ET) were analyzed in an attempt to characterize the clinical and laboratory features in subgroups with thrombosis (T), hemorrhages (H), thrombohemorrhagic events (TH) or a non-thrombohemorrhagic (O) group, and in order to examine survival and the incidence of blastic transformation in the entire group and in the different subgroups. Higher platelet and leukocyte counts were related to hemorrhage (H and TH), prolonged activated partial thromboplastin times and high LDH levels to H while elevated FDP levels were more frequently linked to T. Increased spontaneous platelet aggregation (SPA) was noted in 80.3% of the entire group, independent of whether there was a tendency for thrombohemorrhagic events or not. Bleeding time, as measured by the Duke method, and hemoglobin levels were not different in the various subgroups. Transformation occurred in 11 patients (1.9% per year); seven developed acute leukemia (myeloblastic 4, lymphoblastic 2, megakaryoblastic 1) at a rate of 1.2% per year; and 4 developed other types of chronic myeloproliferative disorders. Nineteen patients died (3.3% per year), six from leukemia (32%), 4 from bleeding (21%) and 9 from unrelated diseases (47%). Survival was estimated to be 65% at ten years, and was significantly longer in females, younger individuals, and the groups with lower leukocyte counts, but did not differ between the subgroups when platelet count and hemoglobin level were considered. Survival was similar in patients with platelet counts between 700-1000 × 10(9)/L and in those with an even higher platelet count. These findings suggest that (1) young female patients with low leukocyte counts may survive longer, (2) SPA is not indicative of either a thrombotic or an hemorrhagic tendency and (3) the limit of the platelet count for establishing the diagnosis of this disorder could perhaps be lowered to 700 × 10(9)/L.