Immune thrombocytopenia

Immune thrombocytopenia (ITP), also known as immune thrombocytopenic purpura, is defined as an autoimmune haematological disorder characterised 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.

Full 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 immunoglobulin (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. Anti-D immunoglobulin can also be considered in those who are rhesus-positive and non-splenectomised. 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 haematological disorder characterised by isolated thrombocytopenia (platelet count <100 × 10⁹/L [<100 × 10³/microlitre]) in the absence of an identifiable cause.[1]Rodeghiero F, Stasi R, Gernsheimer T, et al. Standardization of terminology, definitions and outcome criteria in immune thrombocytopenic purpura of adults and children: report from an international working group. Blood. 2009 Mar 12;113(11):2386-93. http://bloodjournal.hematologylibrary.org/cgi/content/full/113/11/2386 http://www.ncbi.nlm.nih.gov/pubmed/19005182?tool=bestpractice.com The thrombocytopenia is secondary to an autoimmune phenomenon and involves antibody destruction of peripheral platelets.[2]Cooper N, Bussel J. The pathogenesis of immune thrombocytopaenic purpura. Br J Haematol. 2006 May;133(4):364-74. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2141.2006.06024.x http://www.ncbi.nlm.nih.gov/pubmed/16643442?tool=bestpractice.com

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.[3]Cines DB, Bussel JB, Liebman HA, et al. The ITP syndrome: pathogenic and clinical diversity. Blood. 2009 Jun 25;113(26):6511-21. http://bloodjournal.hematologylibrary.org/cgi/content/full/113/26/6511 http://www.ncbi.nlm.nih.gov/pubmed/19395674?tool=bestpractice.com The focus of this topic is primary ITP.