The ultrastructure of the megakaryocytes in idiopathic thrombocytopenic purpura (ITP) in relation to thrombokinetics.

The ultrastructure of megakaryocytes was examined in eight patients with idiopathic thrombocytopenic purpura (ITP) and the results were compared with those obtained from controls and with data obtained from platelet kinetic studies. Platelet production was significantly increased in (ITP) and related to the megakaryocyte number and volume. In all cases of ITP megakaryocytes containing tubular demarcation membranes were found. The granular content and the distribution of the demarcation membrane system in these megakaryocytes from cases of ITP were similar to those features seen in normal cells of the same degree of maturity. In three cases of ITP an increased content of a dilated demarcation membrane system was found in promegakaryocytes and granular megakaryocytes, in one of these cases with the additional formation of large membrane complexes. The ultrastructural findings lend support to the results obtained from the thrombokinetic studies namely that the megakaryocytes in the bone marrow react to thrombocytopenia with an increased production of platelets.