Studies on Thrombopoiesis. I. A Factor in Normal Human Plasma Required for Platelet Production; Chronic Thrombocytopenia Due to its Deficiency

1. A case of chronic thrombocytopenic purpura has been presented in which the pathogenesis appears to be due to congenital deficiency of a platelet-stimulating factor. 2. The factor exists in normal plasma and is stable on storage under normal blood banking conditions and on freezing. 3. The factor appears to act by stimulating megakaryocyte maturation and platelet production in an orderly and sequential manner.