What is the role of anti-muscle-specific kinase (MuSK) antibodies in the evaluation of myasthenia gravis (MG)?

Updated: Aug 27, 2018
  • Author: Abbas Jowkar, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

About half of the patients with negative results for anti-AChR Ab (seronegative MG) may have positive test results for antibody to muscle-specific kinase (MuSK), a receptor tyrosine kinase that is essential for neuromuscular junction development. [46] These patients may represent a distinct group of autoimmune MG, in that they show some collective characteristics that are different from those of anti-AChR–positive patients. [17]

Anti-MuSK–positive individuals tend to have more pronounced bulbar weakness and may have tongue and facial atrophy. They may have neck, shoulder and respiratory involvement without ocular weakness. They are also less likely to respond to acetylcholine esterase (AChE) inhibitors, and their symptoms may actually worsen with these medications. [47, 35]


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