Myasthenia Gravis is a chronic disorder characterized by weakness and rapid fatigue of any of the muscles under your voluntary control. It's caused by a breakdown in the normal communication between nerves and muscles.
The disorder affects only the function of your nerves and muscles, and the muscle weakness you experience improves when you rest. In moderate to severe cases, myasthenia gravis may cause difficulties with speech, chewing, swallowing and breathing, as well as weakness of your limbs.
Myasthenia gravis can affect people of any age, but it's more common in women younger than 40 and in men older than 60. Estimates of the number of people with this disorder vary because it can be difficult to diagnose, but it likely affects between two and three people per every 10,000 in the United States.
Myasthenia gravis can affect any of the muscles that you control voluntarily. It most commonly affects certain muscles, including those of the face, eyes, arms and legs, and those muscles involved in chewing, swallowing and talking. Muscles that control breathing and the movement of your arms and legs can also be involved.
The more often a muscle action is repeated, the worse the weakness becomes. In myasthenia gravis, good days may alternate with bad days. Remissions may occur, however, and can last for months. In rare cases, breathing or swallowing problems worsen markedly, requiring emergency medical care.
There's no cure for myasthenia gravis, but treatments are available to help control the signs and symptoms of the condition.