Platelet aggregation defect in megakaryoblastic leukemia.

Platelet aggregation induced in vitro with ADP, adrenalin and ristocetin was tested in 7 patients with megakaryoblastic leukemia (MKL). All patients had normal or high platelet counts and presented with hemorrhagic diathesis including purpura ecchymosis and epistaxis. Platelet morphology was grossly abnormal and electron microscopy revealed few, or absence of, alpha-granules. Platelet aggregation was reduced in all the cases with at least one aggregating agent. Our studies confirm that MKL is often accompanied by a thrombocytopathy which should be taken into account in the management of these patients.