Immune thrombocytopenia (ITP), also known as immune thrombocytopenic purpura, is defined as an autoimmune hematologic disorder characterized by isolated thrombocytopenia in the absence of an identifiable cause.
Typically found in children often with a preceding viral illness and an abrupt onset. There is a female preponderance among adults, who may present with thrombocytopenia with or without bleeding.
Petechiae occur primarily on the lower limbs, but can appear anywhere on the body (including mucosal membranes), particularly if thrombocytopenia is severe. Bruising is common. Mucosal bleeding may also occur in more severe cases. Intracranial bleeding is reported in less than 1% of adults and less than 0.5% of children.
Complete blood count and peripheral blood smear show isolated thrombocytopenia.
Treatment is based on platelet count and bleeding symptoms. Patients with life-threatening bleeding, regardless of platelet count, can be considered for combination therapy with corticosteroids, intravenous immune globulin (IVIG), and platelet transfusion.
Initial treatment of patients with newly diagnosed ITP includes observation, a corticosteroid, and/or IVIG depending on platelet count and bleeding symptoms. Rho D immune globulin can also be considered in those who are rhesus-positive and nonsplenectomized. Subsequent treatment with mycophenolate, thrombopoietin receptor agonists, rituximab, fostamatinib (adults only), or splenectomy can be considered in patients who are unresponsive to, or intolerant of, initial treatment.
Prognosis is good in children, with up to 80% achieving a spontaneous remission. Mortality is higher in older patients and in those unresponsive to several lines of treatment.
Primary immune thrombocytopenia (ITP) is a hematologic disorder characterized by isolated thrombocytopenia (platelet count <100 × 10³/microliter) in the absence of an identifiable cause.  The thrombocytopenia is secondary to an autoimmune phenomenon and involves antibody destruction of peripheral platelets. 
Secondary ITP includes all forms of ITP where associated medical conditions or precipitants can be identified. The distinction between primary and secondary ITP is clinically relevant because of their different natural histories and distinct treatments, including the need to treat the underlying condition in secondary ITP.  The focus of this topic is primary ITP.
University College London Hospitals
MS has received honoraria from Novartis. MS is the author of a paper cited in this topic.
Dr Marie Scully would like to gratefully acknowledge Professor Francesco Rodeghiero and Dr Marco Ruggeri, previous contributors to this topic.
Director of Benign Hematology
KM declares that he has no competing interests.
Division of Oncology-Hematology
Department of Internal Medicine
University of Nebraska Medical Center
SKR declares that he has no competing interests.
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