Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by varying degrees of weakness of the skeletal (voluntary) muscles of the body. Myasthenia gravis is an autoimmune disease because the immune system–which normally protects the body from foreign organisms–mistakenly attacks itself. The name myasthenia gravis, which is Latin and Greek in origin, literally means “grave muscle weakness.”
Although myasthenia gravis may affect any voluntary muscle, muscles that control eye and eyelid movement, facial expression, and swallowing are most frequently affected. The onset of the disorder may be sudden and symptoms often are not immediately recognized as myasthenia gravis.
Symptoms vary in type and intensity. The first noticeable symptoms of myasthenia gravis may be weakness of the eye muscles, difficulty in swallowing, or slurred speech. It is known for the muscle weakness that increases during periods of activity and improves after periods of rest. 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.
It 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.
Myasthenia gravis can be controlled. With treatment, most individuals with myasthenia can significantly improve their muscle weakness. Some case of myasthenia gravis may even go into remission temporarily. Medications are known to help, as well as surgical procedures, and other therapies.
Some medications improve neuromuscular transmission and increase muscle strength, and some suppress the production of abnormal antibodies. These medications must be used with careful medical follow up because they may cause major side effects. Muscle weakness may even disappear so that medications can be discontinued.
In adults with myasthenia gravis, the thymus gland remains large and is abnormal. It contains certain clusters of immune cells indicative of lymphoid hyperplasia—a condition usually found only in the spleen and lymph nodes during an active immune response. Some individuals with myasthenia gravis develop thymomas (tumors of the thymus gland). Thymomas are generally benign, but they can become malignant. A Thymectomy, the surgical removal of the thymus gland, may help improve symptoms in certain individuals.
Other therapies include plasmapheresis, a procedure in which abnormal antibodies are removed from the blood, and high-dose intravenous immune globulin, which temporarily modifies the immune system and provides the body with normal antibodies from donated blood.
With current therapies, however, most cases of myasthenia gravis are not as “grave” as the name implies. In fact, most individuals with myasthenia gravis have a normal life expectancy. In a few cases, the severe weakness of myasthenia gravis may cause respiratory failure, which requires immediate emergency medical care.
Myasthenia gravis can occur in all ethnic groups and in both genders. It most commonly affects young adult women, under 40, and older men, over 60, but it can occur at any age. It is not directly inherited nor is it contagious.
For more information concerning Myasthenia gravis, be sure to visit your medical doctor.
