Hemostatic Complications Research Articles

A hitherto undescribed defect of platelet coagulant activity in polycythaemia vera and essential thrombocythaemia

A recently described platelet coagulant activity (factor X activating activity) was studied in two patients with essential thrombocythaemia and ten with polycythaemia vera. It was markedly reduced in the five patients with bleeding tendency, and also reduced in one patient with a history of peripheral ischaemia. It was either normal or increased in patients with no haemostatic complications. In the two subjects with lowest activity (five and thirteen percent) and most serious bleeding, chemotherapy resulted in normalisation of the platelet count and of platelet coagulant activity and in disappearance of the bleeding episodes. Our results suggest an association between bleeding tendency and reduced platelet coagulant activity. These findings may be of relevance to 1) the pathogenesis of abnormal bleeding in patients with myeloproliferative disorders and 2) the understanding of the role of platelet coagulant activities other than platelet factor 3 in disturbed haemostasis.