OHSU

Myasthenia Gravis

What is Myasthenia Gravis?

Myasthenia gravis is a neuromuscular (nerve and muscle) disorder. It causes weakness of voluntary muscles (muscles you can control). The weakness often gets better with rest and worse with activity. Myasthenia gravis is an immune system disorder.

Symptoms of Myasthenia Gravis

Symptoms of myasthenia gravis include:

Vision changes:

  • Double vision     
  • Difficulty maintaining steady gaze    
  • Eyelid drooping

Other symptoms of weak muscles:     

  • Swallowing difficulty, frequent gagging or choking     
  • Weakness or paralysis (may get worse with effort later in the day)     
  • Muscles that function best after rest     
  • Drooping head     
  • Difficulty climbing stairs     
  • Difficulty lifting objects     
  • Need to use hands to get up from sitting   
  • Difficulty talking     
  • Difficulty chewing

Additional symptoms that may be associated with myasthenia gravis:       

  • Hoarseness or changing voice      
  • Fatigue      
  • Paralyzed face muscles      
  • Drooling      
  • Breathing difficulty

Causes of Myasthenia Gravis

Your nerves send signals that tell muscles to start moving, or to keep moving once they're active. In myasthenia gravis, these nerve signals do not reach enough of the muscle cells. They are blocked when your immune cells produces antibodies that attach to affected areas, preventing muscle cells from receiving chemical signals (neurotransmitters) from the nerve cell.

Doctors don't yet know what causes immune system disorders such as myasthenia gravis. Some people with myasthenia gravis also have tumors of the thymus (an organ of the immune system). If you have myasthenia gravis, you have a higher risk of other autoimmune disorders such as rheumatoid arthritis or systemic lupus erythematosus.

Myasthenia gravis affects about 3 of every 10,000 people. It can affect people at any age, but is most common in women younger than 40 and men older than 60.