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Causes
By Mayo Clinic staffThe exact cause of ITP isn't known. For that reason it's referred to as idiopathic — meaning "of unknown cause." It is known, however, that in people with idiopathic thrombocytopenic purpura, the immune system malfunctions and begins attacking platelets as if they were foreign substances.
Antibodies produced by your immune system attach themselves to the platelets, marking the platelets for destruction. The spleen, which helps your body fight infection, recognizes the antibodies and removes the platelets from your system. The result of this case of mistaken identity is a lower number of platelets than normal.
Ordinarily, you have anywhere from 150,000 to 450,000 platelets per microliter of circulating blood. As the number of platelets decreases, your risk of bleeding increases. The greatest risk is when your platelet count falls very low — below 10,000 platelets per microliter. At this point, internal bleeding may occur despite a lack of any injury, although this is rare.
In most children with ITP, the disorder follows a viral illness, such as the mumps or the flu. It may be that an infection sets off the immune system, triggering it to malfunction. But ITP in adults isn't linked to infections.
- ITP: Idiopathic thrombocytopenic purpura. American Academy of Family Physicians. http://familydoctor.org/online/famdocen/home/common/blood/113.html. Accessed July 31, 2008.
- What is idiopathic thrombocytopenic purpura? National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/Itp/ITP_WhatIs.html. Accessed July 31, 2008.
- George JN. Treatment and prognosis of idiopathic thrombocytopenic purpura in adults. http://www.uptodate.com/home/index.html. Accessed July 31, 2008.
- Rodeghiero F. Idiopathic thrombocytopenic purpura: An old disease revisited in the era of evidence-based medicine. Haematologica. 2003; 88(10):1081-1087.
- Stasi R, et al. Management of immune thrombocytopenic purpura in adults. Mayo Clinic Proceedings. 2004;79(4):504-522. http://www.mayoclinicproceedings.com/pdf%2F7904%2F7904r.pdf.
- Bussel JB, et al. Eltrombopag for the treatment of chronic idiopathic thrombocytopenic purpura. New England Journal of Medicine. 2007;357(22):2237-2247. http://content.nejm.org/cgi/content/abstract/357/22/2237. Accessed July 31, 2008.
- Rodeghiero F. First-line therapies for immune thrombocytopenic purpura: Re-evaluating the need to treat. European Journal of Haematology. 2008; 80(69)(suppl):19-26.
- Newland A. Emerging strategies to treat chronic immune thrombocytopenic purpura. European Journal of Haematology. 2008;80(69)(suppl):27-33.
