Myasthenia gravis classification
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Charmaine Patel, M.D. [2]
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Overview
Classification
Myasthenia gravis may be classified into 3 subtypes based on presence of autoantibodies.
Pure ocular form
Ocular symptoms are the initial symptom in most of the MG cases. In about 15 percent of these patients this initial symptom will not progress to generalized disease after 2 years and they will classify as pure ocular form of the Myasthenia gravis. In approximately 50 percent of these patients we can’t detect antibodies by classical assay and we need to detect them through cell-based assay.[1]
Generalized form with anti-AChR antibodies
About 85 percent of MG patients develop generalized disease with autoantibody against AchR.[2] These antibodies are IgG1 and IgG3 subclasses which can bind to complement.[3] Thymic abnormalities are more common in this group, especially thymic follicular hyperplasia.[4] this subtype can be further divided into 2 groups:
- Early onset myasthenia gravis (onset of the disease before the age of 50 (EOMG)): In this group we have female predominance with the ratio of 3/1. Thymic follicular hyperplasia is more common in this group and is believed to be related to deregulation of sex hormones and their receptors on thymic cells.[5][6] These patients can have other autoimmune diseases like Hashimoto’s disease.[7]
- Late onset myasthenia gravis (onset of the disease after the age of 50 (LOMG)): Patients with this type of the disease can present with thymoma, a tumor of thymic epithelial cells.[8] In almost 50 percent of them we can find other antibodies like anti-ryanodine antibody, anti-titin antibody and anti-striated muscle antibody.[9] most of the patients in this group have severe symptoms like bulbar involvement.[10]
The forms without classical anti-AChR antibodies
this subtype can be further divided into 3 groups
- The form with anti-anti-MuSK antibodies: About 5 percent of MG patients, especially females has this antibody which belongs to IgG4 subclasses and cannot bind to complement.[11][12] their symptoms are mostly sever and involves facial, bulbar and respiratory muscles but spares ocular and thymic abnormalities.[11][13] In these patients both presynaptic and postsynaptic components of NMJ are affected and the severity of the disease is related to the amount of antibodies.[14][15]
- The form with anti-LRP4 antibodies:
- The form with clustered AChR antibodies:
Neonatal MG
References
- ↑ Leite MI, Jacob S, Viegas S, Cossins J, Clover L, Morgan BP, Beeson D, Willcox N, Vincent A (July 2008). "IgG1 antibodies to acetylcholine receptors in 'seronegative' myasthenia gravis". Brain. 131 (Pt 7): 1940–52. doi:10.1093/brain/awn092. PMC 2442426. PMID 18515870.
- ↑ Vincent A, Newsom-Davis J (December 1985). "Acetylcholine receptor antibody as a diagnostic test for myasthenia gravis: results in 153 validated cases and 2967 diagnostic assays". J. Neurol. Neurosurg. Psychiatry. 48 (12): 1246–52. PMC 1028609. PMID 4087000.
- ↑ Verschuuren JJ, Huijbers MG, Plomp JJ, Niks EH, Molenaar PC, Martinez-Martinez P, Gomez AM, De Baets MH, Losen M (July 2013). "Pathophysiology of myasthenia gravis with antibodies to the acetylcholine receptor, muscle-specific kinase and low-density lipoprotein receptor-related protein 4". Autoimmun Rev. 12 (9): 918–23. doi:10.1016/j.autrev.2013.03.001. PMID 23535160.
- ↑ Berrih S, Morel E, Gaud C, Raimond F, Le Brigand H, Bach JF (January 1984). "Anti-AChR antibodies, thymic histology, and T cell subsets in myasthenia gravis". Neurology. 34 (1): 66–71. PMID 6228745.
- ↑ Eymard B, Berrih-Aknin S (January 1995). "[Role of the thymus in the physiopathology of myasthenia]". Rev. Neurol. (Paris) (in French). 151 (1): 6–15. PMID 7676132.
- ↑ Nancy P, Berrih-Aknin S (May 2005). "Differential estrogen receptor expression in autoimmune myasthenia gravis". Endocrinology. 146 (5): 2345–53. doi:10.1210/en.2004-1003. PMC 1839841. PMID 15661863.
- ↑ Klein R, Marx A, Ströbel P, Schalke B, Nix W, Willcox N (September 2013). "Autoimmune associations and autoantibody screening show focused recognition in patient subgroups with generalized myasthenia gravis". Hum. Immunol. 74 (9): 1184–93. doi:10.1016/j.humimm.2013.06.020. PMID 23792059.
- ↑ Marx A, Pfister F, Schalke B, Saruhan-Direskeneli G, Melms A, Ströbel P (July 2013). "The different roles of the thymus in the pathogenesis of the various myasthenia gravis subtypes". Autoimmun Rev. 12 (9): 875–84. doi:10.1016/j.autrev.2013.03.007. PMID 23535159.
- ↑ Suzuki S, Utsugisawa K, Nagane Y, Suzuki N (2011). "Three types of striational antibodies in myasthenia gravis". Autoimmune Dis. 2011: 740583. doi:10.4061/2011/740583. PMC 3139883. PMID 21785709.
- ↑ Romi F, Aarli JA, Gilhus NE (June 2007). "Myasthenia gravis patients with ryanodine receptor antibodies have distinctive clinical features". Eur. J. Neurol. 14 (6): 617–20. doi:10.1111/j.1468-1331.2007.01785.x. PMID 17539937.
- ↑ 11.0 11.1 Evoli A, Tonali PA, Padua L, Monaco ML, Scuderi F, Batocchi AP, Marino M, Bartoccioni E (October 2003). "Clinical correlates with anti-MuSK antibodies in generalized seronegative myasthenia gravis". Brain. 126 (Pt 10): 2304–11. doi:10.1093/brain/awg223. PMID 12821509.
- ↑ McConville J, Farrugia ME, Beeson D, Kishore U, Metcalfe R, Newsom-Davis J, Vincent A (April 2004). "Detection and characterization of MuSK antibodies in seronegative myasthenia gravis". Ann. Neurol. 55 (4): 580–4. doi:10.1002/ana.20061. PMID 15048899.
- ↑ Leite MI, Ströbel P, Jones M, Micklem K, Moritz R, Gold R, Niks EH, Berrih-Aknin S, Scaravilli F, Canelhas A, Marx A, Newsom-Davis J, Willcox N, Vincent A (March 2005). "Fewer thymic changes in MuSK antibody-positive than in MuSK antibody-negative MG". Ann. Neurol. 57 (3): 444–8. doi:10.1002/ana.20386. PMID 15732104.
- ↑ Le Panse R, Berrih-Aknin S (October 2013). "Autoimmune myasthenia gravis: autoantibody mechanisms and new developments on immune regulation". Curr. Opin. Neurol. 26 (5): 569–76. doi:10.1097/WCO.0b013e328364d6cd. PMID 23995274.
- ↑ Bartoccioni E, Scuderi F, Minicuci GM, Marino M, Ciaraffa F, Evoli A (August 2006). "Anti-MuSK antibodies: correlation with myasthenia gravis severity". Neurology. 67 (3): 505–7. doi:10.1212/01.wnl.0000228225.23349.5d. PMID 16894117.