Immunology => Myasthenia Gravis
Myasthenia Gravis, chronic disease marked by progressive weakness and abnormally rapid fatigue of the voluntary muscles. The muscles affected include those used in walking, breathing, chewing, and talking. A characteristic sign of the disease is drooping eyelids. Myasthenia gravis most often affects women between the ages of 20 and 30, but it can strike anyone after adolescence; after 40, it actually afflicts more men than women.
Myasthenia gravis is one of the noninherited autoimmune diseases, in which the lymphocytes in the blood produce antibodies that destroy muscle-cell sites for the reception of acetylcholine molecules. Acetylcholine normally transmits signals between nerves and muscles, so when its receptors are destroyed it cannot induce muscle contractions. No cure for the disease yet exists, but it can be treated with drugs, called anticholinesterases, that inhibit an enzyme, acetylcholinesterase, that breaks down acetylcholine in the body. The disease may also be relieved by removal of the thymus and by a blood-cleansing process, called plasmapheresis, that removes the destroying antibodies. About 10 per cent of the disease's victims die. For those who survive the first three years, however, there is a chance for stabilization and even for some degree of recovery.