|In myasthenia gravis, muscle weakness often first appears in the muscles of the face, neck and jaw. The arm and leg muscles are affected later.|
Myasthenia gravis (MG) is an autoimmune disease — a disease that occurs when the immune system attacks the body’s own tissues. In MG, that attack interrupts the connection between nerve and muscle — the neuromuscular junction.
The disease first appeared in medical reports in 1672, but didn’t earn its name, which literally means “grave muscular weakness,” until the 1880s.
MG causes weakness in muscles that control the eyes, face, neck and limbs. Symptoms include partial paralysis of eye movements, double vision and droopy eyelids, as well as weakness and fatigue in neck and jaws with problems in chewing, swallowing and holding up the head.
Muscle weakness in MG gets worse with exertion and improves with rest. For more, see Signs and Symptoms .
The cause of MG is unclear. Researchers suspect viruses or bacteria might trigger the autoimmune response; the thymus gland also seems sometimes to play a role in the disease.
Although MG is not hereditary, genetic susceptibility appears to play a role in it and other autoimmune diseases. For more, see Causes/Inheritance .
MG affects women more often then men and tends to begin earlier. The average age of onset in women is 28; the average age of onset in men is 42. In about 10 percent of cases, MG begins in childhood (juvenile onset), which tends to progress slowly and has a high incidence of remission.
MG is treatable with drugs that suppress the immune system or boost the signals between nerve and muscle. Surgeries and other procedures are also helpful in many cases. Most people with the disease are able to manage their symptoms and lead active lives, and a few experience remission lasting many years.
MDA-supported scientists in countries around the world are working to reveal numerous facets of MG, from identifying possible causes and triggers  to the disease's molecular underpinnings to specific treatment strategies. For more, see Research .