Q. My brother-in-law was diagnosed with myasthenia gravis. Could you do one of your columns on this subject so everyone in our family can understand it?

Myasthenia gravis (MG) is a muscle disease. The name comes from Greek and Latin words meaning grave muscle weakness. Myasthenia gravis (my-us-THEEN-ee-uh GRAV-us) affects the muscles that control the eyes, face, breathing, chewing, talking, swallowing and limbs.

MG usually strikes adult women under the age of 40 and men over the age of 60. However, MG can affect people of any age and ethnic group. MG is not contagious and is not inherited.

The cause of MG is a breakdown in the communication between nerves and muscles. This breakdown causes muscle fatigue and weakness, which worsens with repeated use of the muscle. Symptoms usually improve with rest. Treatment can help MG symptoms, but there is no cure for the disease.

The following are some specific signs of MG: drooping eyelids, double or blurred vision, difficulty speaking/swallowing/chewing, inability to smile, shortness of breath, and a change in your stride.

When MG strikes, the immune system produces antibodies that interfere with the muscles' ability to receive nerve signals. This interference causes weakness.

There's a theory that the thymus gland, a part of your immune system located under the breastbone, may be responsible for making these antibodies. The thymus gland is abnormal in most MG cases.

MG symptoms can be intensified by stress, illness, fatigue, extreme heat and drugs such as beta blockers, calcium channel blockers, quinine and some antibiotics.

Myasthenic crisis is a life-threatening condition that occurs when the muscles that control breathing become too weak. Emergency treatment is necessary to recover the ability to breathe properly.

People with MG are more likely to have the following additional problems: a malfunctioning thyroid gland; lupus, a chronic inflammatory disease, and rheumatoid arthritis, an immune-system disorder.

Drugs for treating MG include cholinesterase inhibitors, corticosteroids and immunosuppressants.

Cholinesterase inhibitors enhance communication between nerves and muscles. Corticosteroids inhibit the immune system, limiting antibody production. Immunosuppressants alter your immune system.

Among the therapies for MG are plasmapheresis and intravenous immune globulin. In plasmapheresis, blood is routed through a machine that removes the antibodies interfering with nerve signals to the muscles. Intravenous immune globulin gives your body normal antibodies, which alters your immune-system response.

A thymectomy is the surgical removal of the thymus gland. This surgery is done for people with MG who have tumors, as well as for some who don't have tumors. The surgery improves symptoms in most MG patients.

There are other ways to deal with MG:

Ÿ If you have double vision, use an eye patch. To avoid eyestrain, periodically switch the patch from one eye to the other.

Ÿ Save physical energy by using appliances such as electric toothbrushes and screwdrivers.

Ÿ Eat slowly and rest between bites. More frequent, smaller meals may be easier to handle. Also, try soft foods and avoid sticky foods that require lots of chewing.

Ÿ Install grab bars or railings in places where you may need support, such as next to the bathtub.

MG was first described in detail in the late 19th century, when the outlook for patients was dark. Many died of respiratory failure.

In the 1930s, the nature of MG was better understood; cholinesterase inhibitors became a standard treatment for MG. In the 1960s, researchers discovered the autoimmune nature of MG, and began attacking the disease at its roots using immunosuppressant drugs.

Today the mortality rate of MG is less than 5 percent.

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