Myasthenia gravis (my-uhs-THEE-ne-uh GRA-vis) is an autoimmune disease that causes weakness in the voluntary muscles (the ones you can control).

More to Know

Myasthenia gravis (MG) can affect anyone at any time but is most often diagnosed in women between the ages of 20-40 and men over 50. It's uncommon in children.

With MG, a person develops antibodies that attack a muscle's nerve receptors. These receptors are what give muscles the signal to work. When messages from the nerve to the muscles get blocked by antibodies, weakness results.

Common symptoms of MG are a droopy eyelid; blurred vision; and muscle fatigue in the arms, neck, and legs. Shortness of breath; facial paralysis; and difficulty speaking, chewing, or swallowing also may occur. When MG patients can no longer breathe on their own, they are in "crisis" and need emergency care.

A variety of medications can help treat MG, as can therapies that help purify the blood (like plasmapheresis and IVIG infusion through an intravenous catheter). Having the thymus gland surgically removed, especially if a tumor is present, usually improves symptoms.

Keep in Mind

Myasthenia gravis is a serious condition that is difficult to diagnose. Once identified, however, the prognosis for most MG patients is quite good. Symptoms usually can be controlled and long-term remission is possible.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.