PROGRESS IN HEMATOLOGY Pathophysiology and management of thrombocytopenia: Possible clinical application of TPO receptor agonists Pathophysiology and management of primary immune thrombocytopenia

Primary immune thrombocytopenia, or idiopathic thrombocytopenic purpura (ITP), is an autoimmune disorder characterized by isolated thrombocytopenia due to accelerated platelet destruction and impaired platelet production. Autoantibodies against platelet surface glycoproteins, such as GPIIb/IIIa and GPIb/IX complexes, play major roles in both platelet destruction and impaired platelet production, although autoantibody-independent mechanisms, such as T cell-mediated cytotoxicity, may also be involved in its pathogenesis. Recent advances in the localization of autoantigenic epitopes and the characterization of T cell functional abnormalities in ITP patients have improved our understanding of the pathophysiology of this disease. Although corticosteroids and splenectomy remain central to the treatment of ITP, a new class of drugs, i.e., thrombopoietin receptor agonists (TPO-RAs) and rituximab, have substantially broadened the therapeutic options for refractory ITP patients. Moreover, the success of TPO-RAs in ITP patients shows that reduced platelet production caused by impaired megakaryocytopoiesis plays a greater role in ITP than previously recognized.