What is immune thrombocytopenic purpura (ITP)?

Updated: Jun 28, 2019
  • Author: Craig M Kessler, MD, MACP; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Answer

Immune thrombocytopenic purpura (ITP)—also known as idiopathic thrombocytopenic purpura and, more recently, as immune thrombocytopenia—is a clinical syndrome in which a decreased number of circulating platelets (thrombocytopenia) manifests as a bleeding tendency, easy bruising (purpura), or extravasation of blood from capillaries into skin and mucous membranes (petechiae).

In persons with ITP, platelets are coated with autoantibodies to platelet membrane antigens, resulting in splenic sequestration and phagocytosis by mononuclear macrophages. The resulting shortened life span of platelets in the circulation, together with incomplete compensation by increased platelet production by bone marrow megakaryocytes, results in a decreased platelet count.

Peripheral blood smear from a patient with immune Peripheral blood smear from a patient with immune thrombocytopenic purpura (ITP) shows a decreased number of platelets, a normal-appearing neutrophil, and normal-appearing erythrocytes. ITP is diagnosed by excluding other diseases; therefore, the absence of other findings from the peripheral smear is at least as important as the observed findings. This smear demonstrates the absence of immature leukocytes (as in leukemia) and fragmented erythrocytes (as in thrombotic thrombocytopenic purpura) and no clumps of platelets (as in pseudothrombocytopenia).

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