Myasthenia Gravis Causes

Neuromuscular Junction - Click to see a larger image

Myasthenia Gravis is caused by a breakdown in the communication between nerves and muscles, usually because of an immunological problem. When the nerve sends signals to the muscles to contract a chemical called acetylcholine is released by the nerves. This chemical binds to a specific receptor on the muscle fibers called the acetylcholine receptor.  In myasthenia Gravis a person begins making antibodies against the acetylcholine receptor which destroys these receptors. Therefore the signals to move travel down the nerve but the muscle cannot respond to the acetylcholine. Rare cases of myasthenia gravis can begin in childhood or even in newborns and in these cases there is an inherited defect in part of the acetylcholine release by the nerve and the binding and response at the acetylcholine receptor.
In some cases Myasthenia Gravis can be associated with disorders of other glands including the thymus and the thyroid. All patients diagnosed with myasthenia should have tests done to look at the function of these glands.

The disease should be suspected in anyone with muscle weakness, particularly if there is drooping of the eyes or double vision. The disease is diagnosed by doing blood tests to look for antibodies against the acetylcholine receptor. A new antibody has been discovered as well called the MUSK antibody, which causes a disease identical to Myasthenia Gravis.  EMG/NCS can also be performed to help confirm the diagnosis.