Idiopathic thrombocytopenic purpura pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Pathophysiology
- In most cases, the cause of ITP is autoimmune .[1]
- Auto antibodies against platelets being detected in approximately 60% of cases .
- Most often these antibodies are against platelet membrane glycoproteins IIb-IIIa or Ib-IX, and IgG type.[2]
- Other cause of ITP is due to chronic infections such as HIV, hepatitis C and H. Pylori. It,s due to molecular mimicry, antibody is formed against the infection and this cross-reacts with platelets. Autoantibodies in ITP react with platelet IIb/IIIa glycoprotein, less commonly with GPIb/IX. Lymphocytes in the spleen make the antiplatelet antibody; that,s why splenectomy works so well. There is a correlation between a platelet's short survival and high turnover rate and the subsequent excellent response to splenectomy.
- Platelet kinetic studies show that platelet production is normal or reduced rather than increased in about two thirds of ITP patients.
- autoantibodies from patients with ITP inhibit megakaryocyte growth in vitro.
- IgG from ITP-plasma inhibits megakaryocyte production.
- Ultrastructural studies of the bone marrow in ITP show increased signs of megakaryocyte apoptosis and reduced platelet shedding.
- Recent studies suggests that the stimulus for autoantibody production in ITP is due to abnormal T helper cells reacting with platelet antigens on the surface of antigen presenting cells.[3] This important finding suggests that therapies directed towards T cells may be effective in treating ITP.[4]
References
- ↑ Coopamah M, Garvey M, Freedman J, Semple J (2003). "Cellular immune mechanisms in autoimmune thrombocytopenic purpura: An update". Transfus Med Rev. 17 (1): 69–80. PMID 12522773.
- ↑ Schwartz RS (2007). "Immune thrombocytopenic purpura--from agony to agonist". N. Engl. J. Med. 357 (22): 2299–301. doi:10.1056/NEJMe0707126. PMID 18046034.
- ↑ Semple JW, Freedman J (1991). "Increased antiplatelet T helper lymphocyte reactivity in patients with autoimmune thrombocytopenia". Blood. 78 (10): 2619–25. PMID 1840468.
- ↑ Zufferey A, Kapur R, Semple JW (February 2017). "Pathogenesis and Therapeutic Mechanisms in Immune Thrombocytopenia (ITP)". J Clin Med. 6 (2). doi:10.3390/jcm6020016. PMC 5332920. PMID 28208757.