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.
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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.
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:
Your doctor will ask about your symptoms and medical history. A physical exam will be done. You will likely need to see a neurologist. This type of doctor is an expert in diseases of the nervous system. Tests may include:
Imaging tests to see internal bodily structures may be done with:
Treatment is focused on managing MG symptoms. Talk with your doctor about the best treatment plan for you. Options may include one or more of the following:
Your doctor may prescribe the following:
Plasmapheresis is a procedure that cleans the blood of the abnormal antibodies. This process may need to be repeated at certain intervals.
Thymectomy is a surgical procedure to remove the thymus gland. Surgery may improve symptoms or bring remission in some people.
This may only be needed if breathing is severely impaired. This can happen during an episode of myasthenic crisis.
Therapy does not generally alter the course of the disease. It may be needed to help the person cope with changes in muscle strength. It may also help with learning alternative ways to approach daily activities.
Avoid medications that may worsen MG. Some examples include:
There are no current guidelines to prevent MG.
Myasthenia Gravis Foundation of America
National Institute of Neurological Disorders and Stroke
Myasthenia Gravis Association of BC
Public Health Agency of Canada
Gronseth GS, Barohn RJ. Practice parameter: Thymectomy for autoimmune myasthenia gravis (an evidence-based review): Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2000;55(1):7-15.
Myasthenia gravis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated June 27, 2014. Accessed August 21, 2014.
Myasthenia gravis fact sheet. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/myasthenia_gravis/detail_myasthenia_gravis.htm. Updated April 16, 2014. Accessed August 21, 2014.
What is myasthenia gravis (MG)? Myasthenia Gravis Foundation of America website. Available at: http://www.myasthenia.org/WhatisMG.aspx. Accessed August 21, 2014.
11/9/2015 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Kuo CF, Grainge MJ, Valdes AM, et al. Familial aggregation of systemic lupus erythematosus and coaggregation of autoimmune diseases in affected families. JAMA Intern Med. 2015;175(9):1518-1526.
Last reviewed August 2015 by Rimas Lukas, MD Last Updated: 11/9/2015