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Myasthenia Gravis

A disease in which antibodies made by a person's immune system prevent certain nerve-muscle interactions. It causes weakness in the arms and legs, vision problems, and drooping eyelids or head.

PubMed Health Glossary
(Source: NIH - National Cancer Institute)

About Myasthenia Gravis

Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by varying degrees of weakness of the skeletal (voluntary) muscles of the body. The name myasthenia gravis, which is Latin and Greek in origin, literally means "grave muscle weakness." With current therapies, however, most cases of myasthenia gravis are not as "grave" as the name implies. In fact, most individuals with myasthenia gravis have a normal life expectancy.

The hallmark of myasthenia gravis is muscle weakness that increases during periods of activity and improves after periods of rest. Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often, but not always, involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.

What causes myasthenia gravis?

Myasthenia gravis is caused by a defect in the transmission of nerve impulses to muscles. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control. Normally when impulses travel down the nerve, the nerve endings release a neurotransmitter substance called acetylcholine. Acetylcholine travels from the neuromuscular junction and binds to acetylcholine receptors which are activated and generate a muscle contraction...Read more about Myasthenia Gravis NIH - National Institute of Neurological Disorders and Stroke

What works? Research summarized

Evidence reviews

Corticosteroids for myasthenia gravis

Myasthenia gravis is caused by the body's antibodies impairing transmission of nerve impulses to muscles, resulting in fluctuating weakness and fatigue. Acute attacks can be life threatening because of swallowing or breathing difficulties. Seven randomised controlled trials which included in all 199 participants are published. None fulfilled the presently accepted standards of a high‐quality trial. All these studies have risks of bias and have a weak statistical power. Limited evidence from randomised controlled trials suggests that corticosteroids offer short‐term benefit compared with placebo (dummy treatment). This supports the conclusions of observational studies and expert opinion. Limited evidence from randomised controlled trials does not show any difference in efficacy between corticosteroids and either azathioprine or intravenous immunoglobulin. All trials had design flaws which limit the strength of the conclusions. Further randomised controlled trials are needed.

Plasma exchange for generalised myasthenia gravis

Myasthenia gravis is caused by antibodies in the blood which attack the junctions between nerves and muscles they stimulate. Plasma exchange removes these circulating auto‐antibodies. Many case series suggest that plasma exchange helps to treat myasthenia gravis. Four randomised controlled trials were identified. In the first one, of 14 participants with moderate or severe myasthenia gravis, the myasthenic muscular score after one month was not significantly different for participants treated with plasma exchange and prednisone than for those treated with prednisone alone but there can be only low statistical confidence in the results of this study because of its small size. A randomised controlled cross‐over trial of only 12 participants reported the same efficacy, after four weeks, of plasma exchange or intravenous immunoglobulins for the treatment of moderate to severe myasthenia gravis, but because of bias and a very weak statistical power the data prevent any conclusion. The third, including 87 participants, showed the same efficacy, after two weeks, of plasma exchange or intravenous immunoglobulins for the treatment of myasthenia gravis exacerbation. The fourth randomised controlled trial involving 35 participants reported a benefit from plasma exchange before thymectomy but this trial was heavily biased. No trial addressed the new subtype with antibodies to a muscle specific kinase. Further research is needed to determine the value of long‐term plasma exchange for treating myasthenia gravis and to compare plasma exchange with alternative short‐term treatments for myasthenic crisis or before thymectomy in both types of autoimmune myasthenia.

A review of the use of drugs that suppress the immune system (immunosuppressants) in myasthenia gravis.

Myasthenia gravis (MG) is caused by antibodies produced by the immune system that impair the transmission of nerve impulses to muscles. This results in muscle weakness that characteristically fluctuates. About one person in every 10 000 ‐ 50 000 develops MG each year. The natural history of the disorder is typically a series of exacerbations and remissions. Severe attacks can be life‐threatening because of weakness of muscles involved in swallowing causing choking, and chest muscles causing difficulty with breathing. In MG, immunosuppressant drugs act mainly by reducing the production of antibodies.

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Summaries for consumers

Corticosteroids for myasthenia gravis

Myasthenia gravis is caused by the body's antibodies impairing transmission of nerve impulses to muscles, resulting in fluctuating weakness and fatigue. Acute attacks can be life threatening because of swallowing or breathing difficulties. Seven randomised controlled trials which included in all 199 participants are published. None fulfilled the presently accepted standards of a high‐quality trial. All these studies have risks of bias and have a weak statistical power. Limited evidence from randomised controlled trials suggests that corticosteroids offer short‐term benefit compared with placebo (dummy treatment). This supports the conclusions of observational studies and expert opinion. Limited evidence from randomised controlled trials does not show any difference in efficacy between corticosteroids and either azathioprine or intravenous immunoglobulin. All trials had design flaws which limit the strength of the conclusions. Further randomised controlled trials are needed.

Plasma exchange for generalised myasthenia gravis

Myasthenia gravis is caused by antibodies in the blood which attack the junctions between nerves and muscles they stimulate. Plasma exchange removes these circulating auto‐antibodies. Many case series suggest that plasma exchange helps to treat myasthenia gravis. Four randomised controlled trials were identified. In the first one, of 14 participants with moderate or severe myasthenia gravis, the myasthenic muscular score after one month was not significantly different for participants treated with plasma exchange and prednisone than for those treated with prednisone alone but there can be only low statistical confidence in the results of this study because of its small size. A randomised controlled cross‐over trial of only 12 participants reported the same efficacy, after four weeks, of plasma exchange or intravenous immunoglobulins for the treatment of moderate to severe myasthenia gravis, but because of bias and a very weak statistical power the data prevent any conclusion. The third, including 87 participants, showed the same efficacy, after two weeks, of plasma exchange or intravenous immunoglobulins for the treatment of myasthenia gravis exacerbation. The fourth randomised controlled trial involving 35 participants reported a benefit from plasma exchange before thymectomy but this trial was heavily biased. No trial addressed the new subtype with antibodies to a muscle specific kinase. Further research is needed to determine the value of long‐term plasma exchange for treating myasthenia gravis and to compare plasma exchange with alternative short‐term treatments for myasthenic crisis or before thymectomy in both types of autoimmune myasthenia.

A review of the use of drugs that suppress the immune system (immunosuppressants) in myasthenia gravis.

Myasthenia gravis (MG) is caused by antibodies produced by the immune system that impair the transmission of nerve impulses to muscles. This results in muscle weakness that characteristically fluctuates. About one person in every 10 000 ‐ 50 000 develops MG each year. The natural history of the disorder is typically a series of exacerbations and remissions. Severe attacks can be life‐threatening because of weakness of muscles involved in swallowing causing choking, and chest muscles causing difficulty with breathing. In MG, immunosuppressant drugs act mainly by reducing the production of antibodies.

See all (11)

Terms to know

Antibodies
A protein produced by the immune system in response to a foreign substance such as a virus or bacterium.
Autoimmune Disease
Disease that results when the immune system mistakenly attacks the body's own tissues. Examples include multiple sclerosis, type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus.
Muscles
Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system.
Nerve Impulse
The signal transmitted along a nerve fibre, either in response to a stimulus (such as touch, pain or heat), or as an instruction (such as causing a muscle to contract).
Nerves
A bundle of fibers that receives and sends messages between the body and the brain. The messages are sent by chemical and electrical changes in the cells that make up the nerves.
Receptors
A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific effect in the cell.

More about Myasthenia Gravis

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Other terms to know: See all 6
Antibodies, Autoimmune Disease, Muscles

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