MYASTHENIA GRAVIS

Myasthenia gravis is a disease, which causes progressive fatigue and weakness of the skeletal muscles, especially those of the face, neck, arms, and legs. Muscle weakness occurs when the nerve impulses do not reach the muscle cells to tell them to contract. It is thought that myasthenia gravis is caused by the body having an autoimmune response which blocks the transmission of nerve impulses to muscles. An autoimmune response is when the body produces antibodies against itself.

The cause of the autoimmune response is not known. For some people, it may be due to a tumor of the thymus (a tissue of the immune system). It also may occur with other immune disorders. In many cases, the cause of myasthenia gravis is unknown.

Myasthenia gravis produces weakness in the muscles. The muscles easily tire with use throughout the day or with work. The symptoms are sporadic but get worse over time. The symptoms also get worse with exercise or repeated movements. The muscles of the head, face, and throat are most often involved, but it can affect any muscle group. The disease follows an unpredictable course, sometimes getting worse or ceasing for a while. Drug therapy has improved the lives of persons with myasthenia gravis.

The disease is three times more common in women and first appears most commonly between ages 20 and 40. After age 40 it is equally common in both sexes. About one-quarter of patients have long periods without symptoms.

The onset may be sudden or slow. People often first notice that their muscles tire more quickly. They may have drooping eyelids, double vision, trouble chewing or swallowing, and a weak voice. Usually the affected muscles are strongest in the morning but weaken during the day. Short rest periods help.

As time goes on, more and more muscles become weak. Some may lose function entirely. The symptoms tend to get worse during a woman's period, or with emotional stress, prolonged exposure to sunlight or cold, or infections. If chest muscles are weakened, breathing may be difficult.

The best way to test for myasthenia gravis is by injecting the patient with a certain drug. A rapid improvement within seconds is a positive indication of myasthenia gravis. Special electrical studies of the muscles may also be used for diagnosis. Therapy with medications will counteract symptoms, but they often lose their benefits over time. Some people with myasthenia gravis develop tumors in the thymus gland. Removal of the thymus may help the disease.

An important part of treatment is teaching the person how to cope with the disease. This includes being alert for an approaching crisis, careful timing of medications, and making the most of energy peaks.

For more information, contact the Myasthenia Gravis Foundation of America at (800) 541-5454 or visit their website at www.myasthenia.org.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

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