Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disease that affects the connection between the nerves and skeletal muscles. This can cause progressive muscle weakness.

MG is most common in women less than 40 years old and in men over 60 years old. Infants of mothers with MG are more likely to develop a temporary form.

Myasthenia Gravis Causes

MG occurs when the body’s immune system attacks receptors in muscle. Normally, these receptors respond to a specific chemical, which allows nerve signals to prompt the muscles to move. When the immune system prevents the receptors from working well, the muscles cannot respond to nerve signals.

The thymus is thought to play a role in some cases of MG. The thymus is an organ behind the breastbone that produces immune proteins called antibodies. It is these antibodies that may target the receptors.


Symptoms may grow more severe over time. MG may cause the following:

  • Muscle weakness that increases with muscle use/exercise and improves with rest
  • Drooping eyelids
  • Double and/or blurred vision
  • Difficulty swallowing
  • Difficulty speaking
  • Difficulty walking
  • Weakness of the hand muscles
  • Difficulty breathing


Diagnostic tests may include:

  • Blood tests
  • Electromyography (EMG) tests
  • Repetitive nerve stimulation
  • Pulmonary function testing
  • CT and MRI scans


While there is no cure for MG, we focus treatment on managing your symptoms.


This procedure cleans the blood of the abnormal antibodies. This process may need to be repeated at certain intervals.


A thymectomy removes the thymus gland, which may improve symptoms or bring remission in some patients.

Mechanical Ventilation

You may only need this if breathing is severely impaired during an episode of myasthenic crisis, which occurs when the muscles you use to breathe stop working.

Physical and Occupational Therapy

Therapy does not generally alter the course of the disease, but can help you cope with changes in muscle strength and learn alternative ways to approach daily activities.

Avoiding Medicines That May Worsen Symptoms

Medications that worsen MG include:

  • Beta-blockers
  • Certain antibiotics
  • Certain medications used to treat psychiatric conditions


Content was created using EBSCO’s Health Library. Edits to original content made by Rector and Visitors of the University of Virginia. This information is not a substitute for professional medical advice.