Post-transfusion purpura.

Post-transfusion purpura (PTP) is a rare bleeding disorder caused by alloantibodies specific to platelet antigens. The antibody against the human platelet alloantigen (HPA)-1a is responsible for most of the cases. The majority of affected patients are multiparous women who presumably have been previously sensitized during pregnancy. Blood transfusions rarely have been implicated as the primary cause for alloimmunization in PTP. Thrombocytopenia is usually severe and resolves spontaneously within several weeks. However, patients may develop severe if not fatal bleeding during the course of this disease. The diagnosis is confirmed by demonstrating that the patient's serum contains antibodies to platelet-specific antigens. Treatments for PTP include intravenous immunoglobulin, corticosteroids, and plasmapheresis.