Review: immune thrombocytopenic purpura: an update for immunohematologists.

Immune thrombocytopenic purpura (ITP) is an acquired disease in which autoantibodies to platelets cause their sequestration and destruction by mononuclear macrophages, principally in the spleen. If increased production of platelets by megakaryocytes does not compensate for platelet destruction, the number of circulating platelets decreases (thrombocytopenia), resulting in a characteristic bleeding tendency (purpura). While most children with the disease experience a relatively short and benign clinical course, ITP in adults often lasts more than 6 months (chronic ITP) and is resistant to conventional treatment (corticosteroids, intravenous immune globulin, or splenectomy). The goal of medical management is to increase the platelet count to a safe level, without the risks of bacterial infections associated with splenectomy or toxicity from prolonged corticosteroid therapy. Splenectomy increases platelet counts in hours to days in most patients with acute ITP, but nearly 50 percent experience recurrent thrombocytopenia by 5 years postsplenectomy.