SUNDAY, Aug. 5, 2007 (HealthDay News) -- Myasthenia gravis is chronic weakness -- literally, "grave muscle weakness," according to the term's Greek and Latin roots.
Your eyes droop and can't focus. Walking up stairs or lifting a heavy object become impossible tasks. In worst cases, patients have difficulty breathing or swallowing.
The more you do, the less you can do. The more you exercise, the weaker you get.
No one's sure what causes myasthenia gravis. Worse, there's no solid research that indicates any particular correct way to treat a person with the disease.
"There's a lot of art in the treatment of myasthenia gravis and not a lot of data," said Dr. Michael Benatar, assistant professor of neurology for Emory University, who recently wrote a paper for the American Academy of Neurology reviewing potential therapies for the disease.
Myasthenia gravis is a chronic autoimmune disorder in which the body's own defenses turn on the muscles.
The hallmark of the disease is muscle weakness that increases during periods of activity and improves after periods of rest. The muscles most often involved include those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing, according to the National Institute of Neurological Disorders and Stroke.
Symptoms can include drooping of one or both eyelids and blurred or double vision due to weakness of eye movement muscles -- conditions called ocular myasthenia. Chronic myasthenia can also cause unstable or waddling gait, a change in facial expression, impaired speech and weakness in the arms, hands, fingers, legs, and neck.
"When it affects the swallowing and the breathing muscles, it can be a life-threatening disease if not treated," said Dr. Matthew Meriggioli, an associate professor in the department of neurology at the University of Illinois at Chicago.
A myasthenic crisis occurs when the muscles that control breathing weaken to the point that the patient can't draw in enough oxygen, creating a medical emergency and requiring a respirator for assisted ventilation, according to the National Institutes of Health. The crises happen in patients whose respiratory muscles are weak, and it can be triggered by infection, fever, or a bad reaction to medication.
It is a rare disease. Researchers estimate about 20 people in every 100,000 in the United States have myasthenia gravis, according to the Myesthenia Gravis Foundation of America.
That rarity has worked against those who would cure or find better treatments for the disease, Meriggioli said.
"Getting a drug company to be interested in such a small pool of patients, it's just not cost-effective for them," he said.
The nature of myasthenia gravis also makes it hard to research, Meriggioli said, as the disease's symptoms fluctuate wildly.
"Myasthenia can spontaneously get worse or get better, regardless of treatment," he said. "Trials need to take place over a longer period of time to filter out that randomness, and that is very expensive, especially for a rare disease."
That could explain the results of Benatar's review of research examining treatments for myasthenia gravis.
He looked specifically at whether there were any particular treatments that would alleviate the ocular symptoms of myasthenia gravis, and whether pharmaceutical treatments of symptoms reduced the risk of the disease growing worse.
"There's much less research of adequate quality than you'd expect," Benatar said. "We really turned up empty-handed.
"The most important observation is that there's very little data to steer us toward a best practice," he said. "There's a desperate need for studies to produce better evidence to show how to best treat these people.
Myasthenia gravis can be controlled, even though the evidence is weak for why the treatments work.
Doctors use medications called anticholinesterase agents to help improve neuromuscular transmission and increase muscle strength, according to the National Institute of Neurological Disorders and Stroke. Immunosuppressive drugs may also be used, as they improve muscle strength by suppressing the production of abnormal antibodies. Steroids also have proven useful in suppressing the immune system, Meriggioli said.
The thymus gland is often abnormal in myasthenia gravis patients, and a thymectomy has been shown to reduce symptoms in more than 70 percent of patients and can cure some individuals, possibly by re-adjusting the immune system.
Benatar said he recommends that doctors carefully evaluate the treatments they offer a patient, not always leaping in with the most aggressive tactics.
"Ask yourself to what extent symptoms bother people," he said. "I don't think you need to treat symptoms just because they're there. I would start with the most benign medication, and let the punishment fit the crime.
"But really, we desperately need better quality data to drive therapy," he added.
To learn more, visit the Myasthenia Gravis Foundation of America.