Myasthenia Gravis



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


The root cause of MG is unknown. It occurs when the body’s immune system attacks receptors in muscle. Normally, these receptors respond to the chemical acetylcholine (ACh). This chemical allows nerve signals to prompt the muscles to move. When the immune system prevents these 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. Immune proteins called antibodies are produced there. It is these antibodies that may target the ACh receptors. It is still not clear why the thymus begins to produce these.
The Thymus Gland
si2141 97870 1 thymus gland
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Infants of mothers with MG are more likely to develop a temporary form. It is called neonatal MG. The mother’s abnormal antibodies enter the baby’s bloodstream. When the baby is born, there may be muscle weakness. The abnormal antibodies are often cleared from the baby in about 2 months. This will end the baby’s symptoms.

Risk Factors

MG is most common in women less than 40 years old and in men over 60 years old. People with a family history of systemic lupus erythematosus are also at an increased risk.


Symptoms may grow more severe over time. MG may cause the following:
  • Muscle weakness that increases with muscle use/exercise, and improves after resting those muscles
  • Drooping eyelids
  • Double and/or blurred vision
  • Difficulty swallowing
  • Difficulty speaking
  • Difficulty walking
  • Weakness of the hand muscles
  • Difficulty breathing

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