Idiopathic thrombocytopenic purpura pathophysiology: Difference between revisions
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In many cases, the cause is not actually [[idiopathic]] but [[autoimmune]],<ref>{{cite journal |author=Coopamah M, Garvey M, Freedman J, Semple J |title=Cellular immune mechanisms in autoimmune thrombocytopenic purpura: An update |journal=Transfus Med Rev |volume=17 |issue=1 |pages=69–80 |year=2003 |pmid=12522773}}</ref> with [[antibodies]] against platelets being detected in approximately 60% of patients. Most often these antibodies are against platelet membrane [[glycoprotein]]s IIb-IIIa or Ib-IX, and are of the [[IgG]] type. The famous [[Harrington–Hollingsworth Experiment]] established the immune [[pathogenesis]] of ITP.<ref name="pmid18046034">{{cite journal |author=Schwartz RS |title=Immune thrombocytopenic purpura--from agony to agonist |journal=N. Engl. J. Med. |volume=357 |issue=22 |pages=2299–301 |year=2007 |pmid=18046034 |doi=10.1056/NEJMe0707126}}</ref> | In many cases, the cause is not actually [[idiopathic]] but [[autoimmune]],<ref>{{cite journal |author=Coopamah M, Garvey M, Freedman J, Semple J |title=Cellular immune mechanisms in autoimmune thrombocytopenic purpura: An update |journal=Transfus Med Rev |volume=17 |issue=1 |pages=69–80 |year=2003 |pmid=12522773}}</ref> with [[antibodies]] against platelets being detected in approximately 60% of patients. Most often these antibodies are against platelet membrane [[glycoprotein]]s IIb-IIIa or Ib-IX, and are of the [[IgG]] type. The famous [[Harrington–Hollingsworth Experiment]] established the immune [[pathogenesis]] of ITP.<ref name="pmid18046034">{{cite journal |author=Schwartz RS |title=Immune thrombocytopenic purpura--from agony to agonist |journal=N. Engl. J. Med. |volume=357 |issue=22 |pages=2299–301 |year=2007 |pmid=18046034 |doi=10.1056/NEJMe0707126}}</ref> | ||
The cause of ITP is thought to be related to chronic infections such as HIV, hepatitis C and H. Pylori. The mechanism involved is thought to be MOLECULAR MIMICRY, that is, 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; this is 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. | The cause of ITP is thought to be related to chronic infections such as HIV, hepatitis C and H. Pylori. The mechanism involved is thought to be MOLECULAR MIMICRY, that is, 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; this is 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]]. | ||
The antibodies also appear to damage megakaryocytes, preventing them from releasing | The antibodies also appear to damage [[megakaryocytes]], preventing them from releasing [[platelet]]s. Autoantibody-mediated phagocytosis of platelets has long been thought to be the primary mechanism of the disease. Platelet kinetic studies show that platelet production is normal or reduced rather than increased in about two thirds of ITP patients. Also, [[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. | Ultrastructural studies of the bone marrow in ITP show increased signs of megakaryocyte [[apoptosis]] and reduced platelet shedding. | ||
ITP has a strong association with immune thyroid disease. | ITP has a strong association with immune thyroid disease. | ||
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[[Category:Hematology]] | [[Category:Hematology]] | ||
[[Category:Dermatology]] | [[Category:Dermatology]] | ||
[[Category: | [[Category:Needs overview]] | ||
Revision as of 15:11, 4 March 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Pathophysiology
In many cases, the cause is not actually idiopathic but autoimmune,[1] with antibodies against platelets being detected in approximately 60% of patients. Most often these antibodies are against platelet membrane glycoproteins IIb-IIIa or Ib-IX, and are of the IgG type. The famous Harrington–Hollingsworth Experiment established the immune pathogenesis of ITP.[2]
The cause of ITP is thought to be related to chronic infections such as HIV, hepatitis C and H. Pylori. The mechanism involved is thought to be MOLECULAR MIMICRY, that is, 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; this is 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.
The antibodies also appear to damage megakaryocytes, preventing them from releasing platelets. Autoantibody-mediated phagocytosis of platelets has long been thought to be the primary mechanism of the disease. Platelet kinetic studies show that platelet production is normal or reduced rather than increased in about two thirds of ITP patients. Also, 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.
ITP has a strong association with immune thyroid disease.
Recent evidence 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.
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.