Henry J. Kaminski, MD, FAAN, responds

Thanks to advances in diagnosis and treatment, many people with myasthenia gravis, a rare autoimmune neuromuscular disorder, can expect to lead a normal or near-normal life.

The condition is most often caused by antibodies that block the acetylcholine receptor on the muscle and prevent it from effectively generating an adequate muscle contraction. Antibodies also may affect a protein known as muscle-specific kinase (MuSK), which similarly results in impaired communication at the neuromuscular junction, the structure at which nerves make contact with muscles. In some cases, myasthenia gravis can be associated with disorders or tumors of the thymus gland, a small organ behind the breastbone that plays an important function in the immune and endocrine systems.

One of the hallmarks of the disorder is muscle weakness that worsens after activity and improves with rest. Symptoms and disease progression vary widely among patients, but common characteristics include a droopy eyelid, double vision, trouble swallowing or speaking, and weak arm and leg muscles. Treatment includes these options:

Cholinesterase inhibitors. Pyridostigmine (Mestinon) and other cholinesterase inhibitors help prevent the breakdown of acetylcholine. By boosting the signal to the muscle to contract, these drugs improve strength in some people. Side effects include upset stomach, diarrhea, nausea, and excessive salivation and sweating.

Corticosteroids. Corticosteroids such as prednisone reduce the production of antibodies. However, extended use of steroids could lead to serious side effects including bone thinning, weight gain, diabetes, and an increased risk of some infections.

Immunosuppressants. These drugs—including azathioprine (Imuran), mycophenolate mofetil (Cellcept), cyclosporine (Sandimmune), methotrexate (Trexall), and tacrolimus (Astrograf XL, Prograf)—inhibit the immune system to stop it from damaging the neuromuscular junction. Immunosuppressants can be prescribed with corticosteroids and may take months to take effect.

Around 10 percent of patients are resistant to standard treatment and require more aggressive therapies with more serious side effects. Among these alternate treatments are:

Monoclonal antibodies. Intravenous infusions of rituximab (Rituxan) target B cells, which are involved in autoimmune disorders like myasthenia gravis. In clinical trials, rituximab has been shown to increase the time between relapses. Eculizumab (Soliris) is approved for patients whose disease is positive for the anti-acetylcholine receptor antibody. Side effects for both drugs include fever, chills, aches, nausea, fatigue, diarrhea, and cold symptoms. A more serious side effect with eculizumab is meningococcal disease; patients must be immunized with meningococcal vaccines at least two weeks beforehand.

Plasmapheresis. Sometimes patients can experience a myasthenic crisis—extreme muscle weakness, especially in the diaphragm and chest muscles, which leads to severe breathing problems that require a ventilator. In such cases, doctors may initiate plasmapheresis, a process that involves removing the blood—which also removes the antibodies that block signals from activating the muscle. The antibody-free blood is then transfused back into the patient. The treatment can be effective but can cause a drop in blood pressure, bleeding, muscle cramps, and infections from the catheters used.

Intravenous immunoglobulin. This therapy is used to treat severe or rapidly worsening symptoms, including myasthenic crisis. Patients receive antibodies from healthy donors that block the abnormal antibodies that cause myasthenia gravis. It is also administered before surgery or as a bridge between medications. Side effects include chills, dizziness, and headaches.

Surgery. In patients with tumors on their thymus gland, physicians recommend removing the gland. Such surgery may be effective even for people who don't have a tumor but for whom standard treatments have not worked. In either case, surgery can take months to be effective and patients may still need to take medication.

In addition to medication, neurologists recommend patients get regular exercise and follow a healthy diet. For patients on corticosteroids, doctors suggest daily exercise to prevent bone thinning and a low-salt diet to reduce the risk of weight gain and diabetes. Since prednisone can produce or worsen osteoporosis, patients on the drug should take vitamin D and calcium.

Dr. Kaminski is chairman of the department of neurology at the George Washington University School of Medicine & Health Sciences in Washington, DC.