[Megakaryocytes and platelets in congenital thrombopathies].

Different HT have been studied with the electron microscope and the findings compared to those in the literature. Five patients with thrombasthenia and three with Willebrand's diseases showed various disorders, usually anisocytosis and hypertrophic open canalicular system, in relation to regenerative states. Thirteen young children with 21-trisomy (2 with leukemia) and 13/15 trisomy (1 case) had enlarged platelets with abnormalities of membranes and vacuoles indicating some metabolic disorders and necrotic lesions. One child with Cooley's anemia showed a few granules and necrotic lesions. All these symptoms were related to regenerative or primitive megakaryocytopathias. The lesion of these latter cell appears in other HT: aberrations of membranes in giant platelets syndroms (J. Bernard and J. P. Soulier syndrome), disorders in membranes and/or granules in thrombopenic thrombopathias, the short platelet life span in May-Hegglin anomaly, storage pool disease in Hermansky-Pudlak syndrome. Finally the ultrastructural abnormalities of the platelets mainly help to distinguish several diseases of megakaryocytes.