Thrombopoietin and Platelet Production in Chronic Immune Thrombocytopenia

Since 1968, a greater understanding of platelet biology and its regulation by thrombopoietin (TPO) has emerged. It is now recognized that immune thrombocytopenic purpura (ITP) is a disorder of reduced platelet production as well as increased platelet destruction. New therapies for ITP have emerged that have exploited this new pathophysiologic understanding. This article reviews the biology of TPO, the regulation of its circulating level in ITP, the platelet kinetic data supporting inappropriate platelet production in ITP, and the TPO mimetic agents available to treat ITP.