Which comorbid autoimmune diseases may be present in patients with myasthenia gravis (MG)?

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

MG is an autoimmune disorder, and other autoimmune diseases are known to occur more frequently (13%–22%) in patients with MG than in the general population. Some autoimmune diseases that occur at higher frequency in MG patients are hyperthyroidism, SLE, rheumatoid arthritis, scleroderma, ulcerative colitis, Addison disease, pernicious anemia, red cell aplasia, Sjogren's syndrome, and sarcoidosis. Both acute and chronic inflammatory demyelinating polyneuropathies have been reported in patients with concurrent MG. [35, 36]

Various autoimmune channelopathies, autonomic neuropathy with and without encephalopathy concomitant with the MG and thymoma has also been reported. [37]

MG and inflammatory myopathy is seen in in 5% of cases. Most of these patients have a thymoma with or without myocarditis. Histopathology reveals a giant cell or granulomatous myositis. Elevated CK (not usually seen in MG alone) is commonly found. [38]

MG and thymoma are also reported to have been associated with acquired neuromyotonia or Isaac’s syndrome, rippling muscle disease, and stiff-person syndrome. [39, 40]

A thorough skin and joint examination may help diagnose any of these coexisting diseases. Tachycardia or exophthalmos point to possible hyperthyroidism, which may be present in up to 10-15% of patients with MG. This is important because in patients with hyperthyroidism, weakness may not improve if only the MG is treated.


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