Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by varying degrees of weakness of the skeletal muscles of the body, which are responsble for breathing and moving parts of the body. In myasthenia gravis, the immune system--which normally protects the body from foreign organisms--mistakenly attacks itself. Symptoms vary in type and intensity. The hallmark of myasthenia gravis is muscle weakness that increases during periods of activity and improves after periods of rest. Certain muscles that control eye and eyelid movements, facial expression, chewing, talking, and swallowing are often, but not always, involved. The muscles that control breathing and neck and limb movements may also be affected. Myasthenia gravis is caused by a defect in the transmission of nerve impulses to muscles. Normally when impulses travel down the nerve, the nerve endings release a neurotransmitter substance called acetylcholine. In myasthenia gravis, antibodies produced by the body's own immune system block, alter, or destroy the receptors for acetylcholine. The first noticeable symptoms of myasthenia gravis may be weakness of the eye muscles, difficulty in swallowing, or slurred speech. Other symptoms may include blurred or double vision, drooping eyelid(s), and weakness in the arms, hands, fingers, legs, and neck. Myasthenia gravis is not directly inherited nor is it contagious.
Myasthenia gravis can generally be controlled. Some medications improve neuromuscular transmission and increase muscle strength. These medications must be used with careful medical follow up because they may cause major side effects. Thymectomy, the surgical removal of the thymus gland (which often is abnormal in those with myasthenia gravis), improves symptoms in certain individuals Other therapies include plasmapheresis, a procedure in which abnormal antibodies are removed from the blood, and high-dose intravenous immunoglobulin, which temporarily modifies the immune system and provides the body with normal antibodies from donated blood. However, their effectiveness usually lasts only a few weeks to months.
With treatment, most individuals with myasthenia can significantly improve their muscle weakness. Some case of myasthenia gravis may go into remission temporarily, and muscle weakness may disappear so that medications can be discontinued. In a few cases, the severe weakness of myasthenia gravis may cause respiratory failure, which requires immediate emergency medical care.
New drugs are being tested, either alone or in combination with existing drug therapies, to see if they are effective in treating the disease. Studies are investigating the use of therapy targeting the B cells that make antibodies, (rituximab) or the process by which acetylcholine antibodies injure the neuromuscular junction (eculizumab). The drugs have shown promise in initial clinical trials. Other reseachers are trying to find better ways to diagnose and treat this disorder. For example, NINDS-funded researchers are exploring the assembly and function of connections between nerves and muscle fibers to understand the fundamental processes in neuromuscular development. Other investigators are developing new tools to diagnose people with undetectable antibodies and identify potential biomarkers (signs that can help diagnose or measure the progression of a disease) to predict an individual’s response to immunosuppressive drugs. Information from the National Library of Medicine’s MedlinePlusMyasthenia Gravis
Information sourced through CNF’s partnership with The National Institute of Neurological Disorders and Stroke (NINDS), US National Institutes of Health.