October 28, 2011
Dear Mayo Clinic:
My husband is 82 and has been diagnosed with myasthenia gravis and is now on medication. What is the progression of this immune disorder? How is it treated?
I hope your husband is responding well to his medication. Treatment can manage the symptoms of myasthenia gravis very effectively.
Myasthenia gravis affects nerves' ability to control muscle activity. The disorder causes some muscles to lose strength, usually worsening with repeated or sustained use and improving with rest. In most people with myasthenia gravis, muscle weakness is temporary and reversible, and tends to wax and wane over time. Because the disorder doesn't lead to progressive loss of function or paralysis, the description progressive disease does not really apply. Rather, it's a disease of fluctuating weakness.
A rare condition, myasthenia gravis can occur at any age but is most common in adults. Although the disease is not directly inherited, there is often a personal or family history of other autoimmune diseases. Myasthenia gravis can range from mild to severe. In some cases, symptoms are so minimal that no treatment is necessary. Even in moderately severe cases, with treatment, most people can continue to work and live independently. Life expectancy is normal except in rare cases.
As you note, myasthenia gravis is an immune disorder. In this and other autoimmune diseases, generally, the immune system functions well, fighting infection and other foreign invaders to the body. But it also mistakenly attacks some of the body's own tissue — in this case the neuromuscular junction, where nerve endings release chemical transmitters that stimulate the muscle to contract.
The muscles that control the eyelids and movement of the eyes are most commonly affected, although the disease does not lead to loss of eyesight. In about 10 percent of myasthenia gravis cases, only the eye muscles are affected. In most people, however, symptoms start in the eyes then spread to other muscles, which can include those that control speech, chewing, swallowing or breathing (bulbar muscles), or those of the neck, trunk or limbs.
The effects of myasthenia gravis tend to vary over time. The disease is often directly affected by a person's general health, including physical condition, sleep patterns, hormonal changes, other diseases, medications and even emotional state. Stress and lack of rest are common culprits in aggravating myasthenia gravis symptoms. Maintaining a healthy lifestyle is key to managing the disorder.
Treatment with medications can correct the defective communication between nerves and muscles, thus improving strength. One type of medication boosts the neurochemical communication directly for several hours after each dose. If symptom relief is not adequate, then medications directed at suppressing or modulating immune function may be used. These treatments can involve some medical risks, so they are used only if symptoms are severe. In most cases, the symptoms of muscle weakness are not harmful. In cases where the ability to breathe or swallow safely is compromised, aggressive rescue treatments are available.
About 10 percent of people with myasthenia gravis have a tumor of the thymus gland (located behind the breastbone) that should be surgically removed. Normally, the thymus is active in programming the immune system during early development, and then the gland shrinks during childhood and into adulthood. Reactivated or persisting thymus activity (thymic hyperplasia, seen in 70 percent of patients) may cause or aggravate myasthenia gravis. In some people, particularly those younger than 60 who have generalized disease, removing the thymus gland may reduce disease activity or trigger remission.
No one-size-fits-all treatment program exists for myasthenia gravis. Many options are available, and treatment is tailored to each person. Researchers are looking for a cure or preventive treatment for myasthenia gravis, including a possible vaccine. Fortunately, current treatments control symptoms of this disorder very effectively, and the outlook for a long and productive life is excellent.
— Kathleen McEvoy, M.D., Ph.D., Neurology, Mayo Clinic, Rochester, Minn.