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Causes of Myasthenia gravis

Myasthenia gravis is an autoimmune disease caused by abnormal antibodies carried in the blood stream.

Nerves release a chemical called acetylcholine that activates receptors on muscles to trigger contraction. The myasthenia antibodies interfere with this process by binding to specific sites on the surface of the muscles.

The commonest antibodies are directed against the muscle acetylcholine receptor. In 75% of patients, the abnormal antibody production is associated with abnormalities of a gland in the chest called the thymus, which is part of the immune system.

About 10% of patients have a tumour of the thymus (a thymoma) that is usually benign.

There are very rare genetic abnormalities that cause problems similar to myasthenia gravis. These diseases are called congenital or inherited myasthenias and usually present in infants.

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