Syncope as a Presenting Symptom of MuSK-Associated Myasthenia Gravis

October 2024

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Abstract

Objective

N/A.

Background

Of the different myasthenia gravis (MG) subtypes, dysautonomia has best been characterized in the thymoma group. Cardiac dysfunction and other abnormalities have also been attributed to co-existing autoimmune disorders such as autonomic ganglionopathy. However, further investigation shows qualitative and quantitative evidence of dysautonomia in multiple subgroups without co-existing antibodies. We draw special attention to MuSK-MG where clinical autonomic complaints are often prevalent.

Design/Methods

Cases: We present two cases of recurrent syncope. The first describes a 58-year-old male who develops syncopal episodes and subclinical symptoms of MG following a prostatectomy. He has several hospital visits for syncope before he is hospitalized for a severe orthostatic episode worsened by what is later determined to be a severe myasthenic crisis. He experiences apnea and cardiac arrest. Following stabilization, his MuSK-MG is treated with multiple rounds of steroids and azathioprine before he is able to make a full recovery. The second case is of a 20-year-old female who experiences a year of vasovagal symptoms and tachycardia. She is eventually admitted for respiratory infection triggered respiratory failure in the setting of what is found to be MuSK-MG. She requires rounds of IVIG for stabilization; family declines alternative therapies.

Results

N/A.

Conclusions

In both cases, additional paraneoplastic and autoimmune antibody testing is negative, as well as investigation for a thymoma. These cases underscore the diagnostic complexity of dysautonomia in MG, particularly in MuSK antibody-positive neuromuscular disease. Autonomic instability in these cases may be related to the unique role of MuSK on the formation and maintenance of the neuromuscular junction. There is still much to be elucidated about the role of MUSK and its antibodies. It challenges the conventional diagnostic framework for neuromuscular disease and emphasizes the usefulness of consideration for MuSK in cases of unexplained syncope followed by mild or atypical symptoms of neuromuscular disease.