What Is Myasthenia Gravis?

Myasthenia gravis (MG) is a chronic, autoimmune neuromuscular disease that causes varying degrees of weakness of the skeletal (voluntary) muscles of the body. The name is derived from Greek and Latin and literally means “grave muscle weakness.”

MG is caused by a disorder in the transmission of nerve impulses to the muscles you consciously control. The body’s own antibodies attack the receptors for a neurotransmitter called acetylcholine. Destruction of these receptors interferes with the body’s normal communication between nerves and muscles, causing muscle weakness.

This condition occurs in all ethnic groups and both genders, but most commonly in women under age 40 and men over age 60. It is not directly inherited or contagious. Although a fetus can temporarily get myasthenia gravis from its mother, the symptoms usually disappear within two to three months after birth.

Myasthenia gravis causes progressive muscle weakness during periods of activity. The symptoms then diminish during periods of rest. Most often, the disease affects the muscles that control:

  • Eyes
  • Eyelids
  • Facial expressions
  • Talking
  • Swallowing
  • Chewing

Muscles that control neck, limb movements and breathing can also be affected. In fact, any voluntary muscle can be impacted by this disorder.