Acquired amegakaryocytic thrombocytopenic purpura with humoral inhibitory factor for megakaryocyte colony formation.

A 67-year-old man with thrombocytopenia, and amegakaryocytic but otherwise normal bone marrow, was evaluated. Antibody against thrombocytes was negative and the half-life of thrombocytes was normal. In vitro clonal culture of the patient's bone marrow cells yielded no megakaryocyte colony with normal granulocyte-macrophage and erythroid colony formation. Megakaryocyte colony formation of the control bone marrow cells was significantly suppressed by the addition of the patient's serum to the culture, suggesting the existence of humoral inhibitory factor(s) for megakaryocyte colony formation. Therapeutic trials with plasma exchange, cyclosporine, prednisolone, and cyclosporine plus prednisolone were all unsuccessful, but serious bleeding has been absent.