Myasthenia gravis (MG) is an autoimmune condition that affects the muscles. The muscles are controlled by nerve impulses, or electrical signals sent from the brain. In MG, the body mistakenly attacks the receptors in an area called the neuromuscular junction (the area where nerve signals cross over to the muscle). As more receptor sites are destroyed, the brain is unable to communicate with the muscles, causing muscle weakness in that part of the body.

The exact prevalence of MG isn't known, however it is rare. The Myasthenia Gravis Foundation of America estimates it occurs in up to 20 out of every 100,000 people. About 36,000 to 60,000 Americans are believed to have MG. It can occur in both sexes at any age. However, women tend to be diagnosed before 40, while men are generally diagnosed after 60.

Patients with MG tend to have variable levels of fatigue and weakness. The condition often affects the eyes, leading to a droopy eyelid and blurred or double vision. Other signs may include: problems with speech, difficulty with chewing or swallowing, weakness in the arms, hands, legs or feet, and shortness of breath. In severe cases, breathing may become so difficult the patient needs to be placed on a ventilator (called a myasthenic crisis).

Treating MG

There is no cure for MG. But most patients can be effectively treated well enough to lead productive lives. Medications can improve communication between the nerves and muscles, reduce inflammation and suppress the immune system attack.

In plasmapheresis, the abnormal antibodies are removed from the blood and exchanged with plasma from donors. The effects are temporary because the body will continue making the destructive antibodies. However, plasmapheresis can support the body during times of severe weakness or a crisis.

Another treatment option for some patients is thymectomy, or surgical removal of the thymus gland. Some of the body's immune cells develop in this gland. About 70 percent of patients experience a reduction of symptoms after removal of this gland. In some patients, thymectomy may lead to a remission of MG.

Stem Cell Treatment for MG

Doctors at the University of California, San Diego Medical Center have recently performed an experimental treatment for a patient with severe MG symptoms, called a hematopoietic stem cell transplant. Hematopoietic stem cells are immature cells that develop into blood cells. Some of these blood cells develop into white cells that form part of the immune system.

To perform the transplant, some of the patient's own hematopoietic stem cells are collected. It may take several days to collect enough of the stem cells for the treatment. Specialized CD34 cells are extracted from the blood, purified and stored.

Next, the patient is given chemotherapy to destroy the remaining immune cells. Finally, the purified CD34 cells are reinfused into the body. The cells make their way back to the bone marrow and begin to make new blood cells. Scientists hope new immune cells will not have the memory to attack the body. Thus, the immune system will reset itself, relieving the patient of symptoms.

Transplant Physician Ewa Carrier, M.D., stops short of calling the transplant a cure for MG. He says the disease is believed to be triggered by some type of environmental factor. So, if the patient is exposed to the trigger again, the immune system may once again turn on the body and MG will return. However, investigators are hopeful remission and improved quality of life will last for several years.

Carrier stresses hematopoietic stem cell transplant is very experimental right now. Only a few cases have been done in the U.S. The only other center performing the transplant is Northwestern University in Chicago. A large, national study is needed to confirm the safety/benefits of the treatment for MG patients.

For information on a clinical trial at Northwestern University in Chicago, log onto http://www.clinicaltrials.gov. Type the trial identification number in the search box: NCT00424489.

For general information on myasthenia gravis:

Muscular Dystrophy Association

Myasthenia Gravis Foundation of America

National Institute of Neurological Disorders and Stroke