What is it?
Myasthenia Gravis (MG) is a chronic autoimmune neuromuscular disorder that is characterized by fluctuating weakness of the voluntary muscle groups. The muscles frequently involved are the ones that control eye movements, eyelids, chewing, swallowing, coughing and facial expression. Muscles that control breathing and movements of the arms and legs also may be affected. An estimated 20 in 100,000 Americans live with MG. However, the disorder probably is under diagnosed and the number may be higher.

What causes it?
The voluntary muscles of the entire body are controlled by nerve impulses that arise in the brain. These nerve impulses travel down the nerves to the place where the nerves meet the muscle fibers. Nerve fibers do not actually connect with muscle fibers. There is a space between the nerve ending and muscle fiber; this space is called the neuromuscular junction.

When the nerve impulse originating in the brain arrives at the nerve ending, it releases a chemical called acetylcholine. Acetylcholine travels across the space to the muscle fiber side of the neuromuscular junction where it attaches to many receptor sites. The muscle contracts when enough of the receptor sites have been activated by the acetylcholine. In MG, there is as much as an 80% reduction in the number of these receptor sites. The reduction in the number of receptor sites is caused by an antibody that destroys or blocks receptor sites more rapidly than the body can replace them. Muscle weakness occurs when acetylcholine cannot activate enough receptor sites at the neuromuscular junction.

How does it affect my job?
Muscle weakness and generalized fatigue are significant factors for persons in the workplace who have MG. Because the symptoms and effects of MG vary among individuals, the workplace experience also is varied. For example, some individuals may not be able to work in certain jobs; other individuals may need accommodations such as altered work schedules or telecommuting arrangements; and some individuals may experience no effect on their jobs from MG. Another consequence of MG on one’s job is caused by the fact that the disease is not always apparent to others. As a result, co-workers often do not realize that the person with MG is suffering from weakness, fatigue or other symptoms, and they may misinterpret the MG affected co-worker’s behavior as a failure to be a “team player” or share the workload.

Can it be prevented or treated?
There is no known cure for MG, but there are effective treatments that allow many, but not all people with MG, to lead full lives. Common treatments include medications, thymectomy (surgical removal of the thymus gland) and plasmapheresis (plasma exchange). Spontaneous improvement, even remission, may occur without specific therapy.

Current treatments for MG are sufficiently effective that most patients will have significant improvement in their muscle weakness. In some cases, MG may go into remission for a time period when no treatment is necessary. Research plays an important role in finding new answers and treatments for MG.