It is caused by a malfunction in communication between nerves and muscles. The disease is manifested mostly by weakness in the muscles, most often the muscles that control swallowing and eye movement, less frequently the muscles of the arms and legs. Symptoms include double vision, droopy eyelids, difficulty chewing, smiling, talking, swallowing and breathing. Other muscles that are sometimes affected include the forearms, neck, legs and shoulders. The disease is usually localized and does not cause generalized muscle fatigue.
Symptoms usually increase during activity and decrease during rest periods.
Although incurable, myasthenia gravis can be successfully treated so that the patient goes into remission and can live a relatively normal lifestyle. When myasthenia gravis affects the breathing, the patient may need to be hospitalized and placed on machines that assist breathing. The disease usually reaches its peak in the early years of onset and is not then continuously progressive. There is however wide variation in symptoms throughout a typical day, with fatigue progressing throughout. The stress of surgery or radiation therapy can make MG worse.