Thrombocytopathy in Preleukaemia: Association with a Defect of Thromboxane A2 Activity

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Abstract
Platelet aggregation and the platelet prostaglandin pathway were investigated in 2 patients with preleukemic states who had a hemorrhagic tendency but a normal platelet count. In both patients platelet aggregation induced by collagen ADP and arachidonic acid (AA) were abnormal. Malonyldialdehyde (MDA) production from exogenous AA was normal in both patients, thus excluding cyclo-oxygenase deficiency. The platelet aggregating and rabbit aorta contracting activities of thromboxane A2 (TxA2) were very low in both patients. Production of thromboxane B2 (TxB2) assessed by TLC separation of the metabolites of [1-14C]AA and by radioimmunoassay, was normal. These abnormalities of platelet function appear to be due to the production of TxA2 with a low biological activity.