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Doctors Note Progress Against Muscle-Wasting Disease

New treatments for myasthenia gravis offer people the prospect of a full life

WEDNESDAY, June 23, 2004 (HealthDayNews) -- You feel your eyelids drooping as the day goes on, or perhaps find your speech slurring in the afternoon or evening.

Your arms and limbs become difficult -- if not impossible -- to move. You can't chew properly, or swallow, or even draw a good breath.

These are the symptoms of myasthenia gravis, an autoimmune disease that affects an estimated one of every 5,000 Americans and can become life-threatening without treatment.

Myasthenia gravis occurs when the body's immune system begins attacking the neuromuscular junction, the point where nerve impulses are transferred to muscles. This causes the muscles to misfire and grow weaker and weaker with continued use.

"The disease can become so severe that it can affect a patient's breathing process to the point where they need to be put on a breathing machine," said Dr. Henry Kaminski, director of the Myasthenia Gravis Center at the University Hospitals of Cleveland.

With June designated as Myasthenia Gravis Awareness Month, neurologists are working to spread the word about the unusual nerve disease.

Most important, they want people to know that while the disease is called myasthenia gravis -- the Greek and Latin words meaning grave muscular weakness -- it no longer should be a fatal disease.

"It really used to be myasthenia gravis -- it put people in the grave," Kaminski said. "But now we can say with modern treatment that patients can enjoy a normal life span."

Normally when impulses travel down the nerve, the nerve endings release a neurotransmitter substance called acetylcholine, according to the National Institute of Neurological Disorders and Stroke. The substance travels through the neuromuscular junction and binds to special receptors, activating them and causing a muscle contraction.

In myasthenia gravis, antibodies interfere with the receptors for acetylcholine at the neuromuscular junction, and that prevents the muscle contraction from occurring.

This leads to the hallmark of myasthenia gravis -- muscle weakness that increases during periods of activity and improves after periods of rest.

The thymus gland is believed to be linked to myasthenia gravis. The gland, which lies in the upper chest area beneath the breastbone, plays an important role in the development of the immune system in early life. In adults with myasthenia gravis, the thymus gland is abnormal, and some people with myasthenia gravis develop thymomas, or tumors on the thymus gland.

The relationship between the thymus gland and myasthenia gravis is not yet fully understood. Scientists believe the thymus gland may give incorrect instructions about the production of the acetylcholine receptor antibodies, thereby setting the stage for the attack on neuromuscular transmission.

Anyone, regardless of age, race or gender, can become afflicted with myasthenia gravis. The disorder is not directly inherited nor is it contagious, although it occasionally may occur in more than one member of the same family.

The degree of muscle weakness involved in myasthenia gravis varies greatly among patients, according to doctors.

In most cases, the first noticeable symptom is weakness of the eye muscles, which can cause blurred or double vision or a drooping of one or both eyelids. In others, difficulty in swallowing and slurred speech may be the first signs.

Other symptoms include:

  • An unstable or waddling gait;
  • Weakness in arms, hands, fingers, legs and neck;
  • A change in facial expression;
  • Shortness of breath.

The most serious health threat from the disorder comes when it causes the voluntary muscles that control breathing to stop working, in what is known as a "myasthenia failure."

The death rate associated with myasthenia gravis steadily declined during the 20th century, said Dr. James Howard Jr., a professor of neurology with the University of North Carolina.

In the 1930s and 1940s, more than 80 percent of people with the disease died, Howard said. By the middle of the century, that number had declined to about 50 percent.

It wasn't until the 1970s that doctors knew enough about the disease to effectively treat it, he said.

"Originally it was thought that the nerve did not release enough chemical transmitter," Howard said. But breakthrough research discovered that the nerve was healthy, but under constant attack from the body's immune system.

"Now, today, no one should die of myasthenia gravis," Howard said. "Everyone should live."

There are several therapies now available to help reduce and improve muscle weakness. Medications used to treat the disorder include drugs such as neostigmine and pyridostigmine, which help improve neuromuscular transmission and increase muscle strength.

Immunosuppressive drugs such as prednisone, cyclosporine and azathioprine also may be used. These medications improve muscle strength by suppressing the production of abnormal antibodies, but must be taken with careful medical follow-up because they may cause major side effects, experts say.

Thymectomy, the surgical removal of the thymus gland, has been found to improve symptoms in more than 50 percent of patients. Other treatments for myasthenia gravis include plasmapheresis, a process in which abnormal antibodies are removed from the blood, and high-dose intravenous immune globulin, which temporarily modifies the immune system and supplies the body with normal antibodies from donated blood, according to the National Institute of Neurological Disorders and Stroke.

More information

For more information, visit the Myasthenia Gravis Foundation of America.

SOURCES: Henry Kaminski, M.D., director, Myasthenia Gravis Center, University Hospitals of Cleveland; James Howard Jr., M.D., professor, neurology, University of North Carolina, Chapel Hill
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