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EDITORIAL COMMENTARY
Year : 2020  |  Volume : 23  |  Issue : 1  |  Page : 6
 

Grave prognosis of the musclespecific kinase (MuSK)-positive myasthenia gravis (MG): A false prejudice


Department of Neurology, Kuala Lumpur Hospital, Kuala Lumpur, Malaysia

Date of Submission06-Nov-2019
Date of Acceptance06-Nov-2019
Date of Web Publication21-Jan-2020

Correspondence Address:
Dr. Fu Liong Hiew
Physician and Neurologist, Department of Neurology, Kuala Lumpur Hospital, Jalan Pahang, 50586, Wilayah Persekutuan, Kuala Lumpur
Malaysia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/aian.AIAN_579_19

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How to cite this article:
Hiew FL. Grave prognosis of the musclespecific kinase (MuSK)-positive myasthenia gravis (MG): A false prejudice. Ann Indian Acad Neurol 2020;23:6

How to cite this URL:
Hiew FL. Grave prognosis of the musclespecific kinase (MuSK)-positive myasthenia gravis (MG): A false prejudice. Ann Indian Acad Neurol [serial online] 2020 [cited 2020 Feb 26];23:6. Available from: http://www.annalsofian.org/text.asp?2020/23/1/6/272645




A widely held clinical and immune pathomechanism concern among clinicians are muscle-specific kinase (MuSK)-positive Myasthenia gravis (MG), wherein patients often have more severe presentation based on its distinctive phenotype of predominant cranial and bulbar weakness with occurrence of muscle atrophy, poor response to standard immunotherapies including IV immunoglobulin, and higher rate of life-threatening crisis.[1],[2] Anti-MuSK antibodies are predominantly of IgG4 subclass, which differs from the classical acetylcholine receptor (AChR) antibodies in terms of mode of action, primarily due to its inability to activate complement and is unable to induce antigenic modulation.[3],[4]

In this issue of AIAN, Samal and colleagues presented their experience on MG patients with different antibody status, comparing the clinical characteristics, treatment response to immunosuppressants, longterm prognosis, and quality of life.[5] The study included 23 patients with MuSK+ve, 55 with AChR+ve, and 9 with doubleseronegative myasthenia. They did not find any significant difference in all clinical parameters and outcomes. Comparable good response to treatment was observed in MuSK+ve MG with conventional immunosuppressant drugs (azathioprine and mycophenolate mofetil) similar to AChR+ve MG. Consequently, MuSK+ve MG has a nonsignificant increase in odds of developing the severe disease (adjusted odds ratio [OR] 1.27, CI 0.72–2.24) or poor outcome (adjusted OR 1.93, CI 0.69–5.42) compared with AChR+ve MG.

Collectively, results by Samal et al. and previously published studies demonstrated similar long-term outcomes between MuSK+ve and AChR+ve MG.[6],[7] These series of analyses provided additional reassurance that the findings on the overall treatment outcome of MuSK+ve MG patients are consistent. Therefore, the use of aggressive therapy, for example, rituximab should only be started in patients' refractory or intolerance to conventional immunosuppressants, and not based on their antibody status. Certainly, treatment plan and prognosis should be based on overall clinical response and not guided by immune biomarkers alone.



 
   References Top

1.
Evoli A, Alboini PE, Damato V, Iorio R, Provenzano C, Bartoccioni E, et al. Myasthenia gravis with antibodies to MuSK: An update. Ann N Y Acad Sci 2018;1412:82-9.  Back to cited text no. 1
    
2.
Gilhus NE, Tzartos S, Evoli A, Palace J, Burns TM, Verschuuren JJGM. Myasthenia gravis. Nat Rev Dis Primers 2019;5:30.  Back to cited text no. 2
    
3.
Gilhus NE, Skeie GO, Romi F, Lazaridis K, Zisimopoulou P, Tzartos S. Myasthenia gravis – autoantibody characteristics and their implications for therapy. Nat Rev Neurol 2016;12:259-68.  Back to cited text no. 3
    
4.
Koneczny I, Stevens JA, De Rosa A, Huda S, Huijbers MG, Saxena A, et al. IgG4 autoantibodies against muscle-specific kinase undergo Fab-arm exchange in myasthenia gravis patients. J Autoimmun 2017;77:104-15.  Back to cited text no. 4
    
5.
Samal P, Goyal V, Singh MB, Srivastava P. MuSK (Muscle Specific Kinase) positive myasthenia: Grave prognosis or undue prejudice? Ann Indian Acad Neurol 2019. doi: 10.4103/aian.AIAN_302_19.  Back to cited text no. 5
    
6.
Deymeer F, Gungor-Tuncer O, Yilmaz V, Parman Y, Serdaroglu P, Ozdemir C, et al. Clinical comparison of anti-MuSK- vs anti-AChR-positive and seronegative myasthenia gravis. Neurology 2007;68:609-11.  Back to cited text no. 6
    
7.
Guptill JT, Sanders DB, Evoli A. Anti-MuSK antibody myasthenia gravis: Clinical findings and response to treatment in two large cohorts. Muscle Nerve 2011;44:36-40.  Back to cited text no. 7
    




 

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