Myasthenia gravis is an autoimmune disease affecting the neuromuscular junction and producing weakness of voluntary muscles. It is a chronic disease. The disorder mostly happen between the ages of 20 and 50, with women developing symptoms younger and men developing symptoms later. The weakness is called by a defect in the transmission of nerve impulses to muscles. The disease is seldom fatal, though it can be life-threatening when muscle weakness interferes with respiration. MG often involves muscles that control eye and eyelid movement, facial expression, chewing, talking, and swallowing. 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. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction – the place where nerve cells connect with the muscles they control. Some factors can make myasthenia gravis worse, including fatigue, illness, stress, extreme heat, and some medications, such as beta blockers, calcium channel blockers, quinine and some antibiotics. MG may be associated with other autoimmune diseases. Patients with family members who suffer from disorders such as rheumatoid arthritis, scleroderma, and lupus may have an increased risk for myasthenia gravis.
Some people find their symptoms disappear spontaneously and don’t return for many years. Just how weak the muscles are when symptoms do persist also varies from person to person.
Signs and symptoms may include:
* Facial muscle weakness, including drooping eyelids
* Double vision
* Difficulty in breathing, talking, chewing or swallowing
* Muscle weakness in your arms or legs
* Fatigue brought on by repetitive motions
A very specific test for MG is a blood test to look for serum antibodies to acetylcholine receptor. Eighty percent of all patients with MG have abnormally elevated serum levels of these antibodies, but positive test results are less likely in patients with mild or purely ocular forms. The chance of receiving a falsely positive test result from a reputable laboratory is small, although borderline tests should be repeated.
Some medications improve neuromuscular transmission and increase muscle strength, and some suppress the production of abnormal antibodies. Steroids and other immuno-suppressive drugs are often very effective and produce remission of symptoms by suppressing the body’s immune system. Unfortunately these drugs can also have serious effects, especially after prolonged use.
Thymectomy, the surgical removal of the thymus gland, improves symptoms in certain patients and may cure some individuals, possibly by re-balancing the immune system.