Drooping eyelids, double vision, and unexplained muscle weakness in the arms and legs are classic warning signs of myasthenia gravis. However, recent medical research indicates that other autoimmune conditions frequently appear long before these neuromuscular symptoms manifest—occurring at more than twice the rate of the general population over a ten-year span, and spiking to more than four times as high in the two years immediately preceding diagnosis.
Samsung Medical Center announced that these findings were published in the September 8 issue of the international medical journal Neurology. The study was supervised by corresponding author Professor Min Ju-hong of Samsung Medical Center, with Professor Kwon Soon-wook of Inha University Hospital serving as first author, alongside Professor Han Kyung-do of Soongsil University.
A Fourfold Increase in the Two Years Before Diagnosis
Autoimmune diseases occur when the body’s immune system mistakenly attacks its own healthy tissues. Conditions such as systemic lupus erythematosus, Sjogren syndrome, and autoimmune thyroid disease fall into this category. Myasthenia gravis operates similarly, causing immune-mediated disruption in signal transmission between nerves and muscles, which leads to drooping eyelids, double vision, extremity weakness, and difficulty swallowing.
The research team analyzed National Health Insurance Service (NHIS) claims data from 2010 to 2021, tracking 8,355 myasthenia gravis patients aged 20 and older alongside a control group of 83,550 age- and sex-matched individuals from the general population.
Over the ten-year period prior to diagnosis, the overall incidence of autoimmune diseases among myasthenia gravis patients was 2.12 times higher than that of the control group. When narrowing the timeframe to the two years directly before diagnosis, the incidence rate rose to 4.27 times higher.
Looking at specific conditions over the ten-year pre-diagnosis window, systemic lupus erythematosus occurred 4.87 times more frequently, Sjogren syndrome 4.75 times more frequently, and autoimmune thyroid disease 3.66 times more frequently. Seropositive rheumatoid arthritis was 2.45 times as common. Conversely, the analysis found no statistically significant link between myasthenia gravis and inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease, though researchers noted that the small number of cases requires cautious interpretation.
Shared Genetics and Immune Dysregulation
Researchers attribute this clinical clustering to shared genetic traits that make the immune system generally more prone to targeted self-attack. Individuals carrying these underlying genetic traits may be inherently vulnerable to developing multiple autoimmune conditions—ranging from systemic disorders like lupus to neuromuscular conditions like myasthenia gravis.
Furthermore, when immune responses are improperly regulated, the body produces autoantibodies that directly interfere with acetylcholine receptors or related proteins at the neuromuscular junction, blocking signal transmission and triggering symptom onset.
"If a patient with an existing autoimmune condition, such as lupus or autoimmune thyroid disease, repeatedly experiences drooping eyelids or decreasing muscle strength, they should keep myasthenia gravis in mind and promptly seek evaluation from a specialist," said Professor Min Ju-hong.
While myasthenia gravis is a chronic condition, medical experts emphasize that it generally responds well to therapeutic management. In South Korea, it is classified under the National Health Insurance special copayment program for rare diseases. Once a diagnosis is confirmed and registered, patient out-of-pocket costs for covered medical care are capped at 10%. Following a decision by the Ministry of Health and Welfare's Health Insurance Policy Deliberation Committee, that copayment rate will drop to 7% starting in December, and further decrease to 5% in the first half of 2028.
