People with myasthenia gravis (MG) were more likely to have certain autoimmune diseases in the years before their MG diagnosis, with the greatest difference occurring within the two years immediately preceding diagnosis, according to a large population-based study from South Korea published recently in Neurology.
“However, the temporal relationship between autoimmune diseases and MG remains unclear,” the study’s authors said.
These findings suggest that MG may develop as part of a broader pattern of autoimmune activity, although they do not establish that another autoimmune disease causes MG.
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Researchers used health insurance records from South Korea from 2010 through 2021. They compared 8,355 adults with MG with 83,550 people of similar age and sex who did not have MG. The average age of the people in the study was 53.7 years, and 44.1% were men. Researchers looked at whether people had any of eight other autoimmune diseases during the 10 years before their MG diagnosis.
Overall, people with MG were more than twice as likely to have had another autoimmune disease during the 10 years before their MG diagnosis compared with people who did not have MG. The difference was even greater in the two years immediately before an MG diagnosis.
Read more about MG causes and risk factors
During that period, people with MG were more than four times as likely to have had another autoimmune disease. This suggests that autoimmune diseases may occur together more often around the time MG develops or is diagnosed.
Importantly, the study does not show that having another autoimmune disease causes MG.
The strongest connections were seen with lupus, Sjögren’s disease, autoimmune thyroid disease and rheumatoid arthritis. People with MG were nearly five times as likely to have lupus or Sjögren’s disease, more than three times as likely to have autoimmune thyroid disease and more than twice as likely to have rheumatoid arthritis during the 10 years before their MG diagnosis. Psoriasis and type 1 diabetes were also more common among people with MG, but this was seen only during the two years immediately before the MG diagnosis.
Crohn’s disease and ulcerative colitis were not associated with MG in the analysis. The researchers cautioned that the study relied on administrative health insurance claims, which can lack detailed clinical information and may introduce limitations in how diseases are identified.
For patients, the findings reinforce that having an autoimmune disease does not mean MG will necessarily develop. However, people with autoimmune conditions who develop symptoms consistent with MG, such as fluctuating muscle weakness, drooping eyelids or difficulty swallowing, should discuss those symptoms with a health care professional. The study may also help researchers better understand how autoimmune diseases overlap and how MG develops.
Learn more about autoimmune disease: “What is the role of the immune system in myasthenia gravis?”
