ACQUIRED AMEGAKARYOCYTIC THROMBOCYTOPENIC PURPURA WITH HUMORAL INHIBITORY FACTOR FOR MEGAKARYOCYTE COLONY FORMATION

A 67-year-old man with thrombocytopenia, and amegakaryocytic but other wise normal bone marrow, was evaluated. Antibody against thrombocytes was negative and the half-life of thrombocytes was normal. In vitro cl onal culture of the patient's bone marrow cells yielded no megakaryocy te colony with normal granulocyte-macrophage and erythroid colony form ation. Megakaryocyte colony formation of the control bone marrow cells was significantly suppressed by the addition of the patient's serum t o the culture, suggesting the existence of humoral inhibitory factor(s ) for megakaryocyte colony formation. Therapeutic trials with plasma e xchange, cyclosporine, prednisolone, and cyclosporine plus prednisolon e were all unsuccessful, but serious bleeding has been absent.