What causes MG?
With MG, normal communication between the nerve and muscle is stopped at the place where nerve endings connect with the muscles they control—the nerve-muscle junction. Normally, the nerve endings release a substance called acetylcholine (uh-SET-uhl-KOH-LEEN), which binds to the muscle tissue at the nerve-muscle junction, causing the muscle to contract (move). In someone with MG, the body’s own immune system makes antibodies that block the binding of acetylcholine to the muscle. The thymus gland, part of the immune system, is abnormal in most MG cases. Some people with MG have benign tumors of the thymus gland called thymomas. Doctors do not fully understand the relationship between the thymus gland and MG.
MG is caused by a defect in the transmission of nerve signals to muscles. Normally, nerve endings release a substance called acetylcholine that binds or attaches to receptors on the muscle. This leads to muscle contractions. In MG, the body’s own immune system produces antibodies that block this transmission.
