ISCHEMIC STROKE AS FIRST MANIFESTATION OF ESSENTIAL THROMBOCYTHEMIA -REPORT OF 6 CASES

Background Ischemic stroke as a presenting sign of essential thrombocy themia has been infrequently reported. We describe six patients in who m cerebrovascular disease was the first manifestation of this myelopro liferative disease. A positive endogenous megakaryocyte and/or erythro id colony growth from blood was a diagnostic criterion of essential th rombocythemia in patients with platelets counts lower than 600 x 10(9) /L. Case Descriptions These six patients represented 0.54% of all pati ents with first stroke, 42.8% of all hematologic disorders associated with stroke, and 12.5% of all patients with essential thrombocythemia diagnosed from 1986 to 1992 at our institution. Eleven acute cerebrova scular accidents (6 transient ischemic attacks, 5 definitive cerebral infarcts) were registered. Mean time from ischemic stroke to diagnosis of essential thrombocythemia was 4.5 months (range, 1 to 12 months). The mean platelet count was 597 x 10(9)/L (range, 414 to 760 x 10(9)/L ). Four patients had platelets counts lower than 600 x 10(9)/L. All pa tients had circulating erythroid progenitors, megakaryocytic progenito rs, or both. Conclusions Ischemic stroke as a presenting manifestation of essential thrombocythemia is probably underrecognized. The diagnos is of thrombocythemia should not be excluded on the basis of platelet counts lower than 600 x 10(9)/L. The availability of in vitro culture of hematopoietic progenitors from peripheral blood makes it possible t o diagnose early and atypical cases.