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All about myasthenia gravis causes of myasthenia gravis risk factors for myasthenia gravis thymus gland signs and symptoms of myasthenia gravis diagnosis of myasthenia gravis myasthenia gravis treatment myasthenic crisis myasthenia gravis and pregnancy prognosis of myasthenia gravis

What causes myasthenia gravis?

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. Normally when impulses travel down the nerve, the nerve endings release a

neurotransmitter substance called acetylcholine. Acetylcholine travels through the neuromuscular junction and binds to acetylcholine receptors which are activated and generate a muscle contraction.

In myasthenia gravis, the immune system attacks a receptor on the surface of muscle cells. This prevents the muscle from receiving the nerve impulses that normally make it respond. Myasthenia gravis affects "voluntary" muscles, which are those muscles under conscious control responsible for movement. It does not affect heart muscle or the "smooth" muscle found in the digestive system and other internal organs.

During fetal development, the immune system generates many B cells that can make autoantibodies, but B cells that could harm the body's own tissues are screened out and destroyed before birth. It is possible that the stage is set for myasthenia gravis when some of these cells escape detection. Genes controlling other parts of the immune system, called MHC genes, appear to influence how susceptible a person is to developing autoimmune disease. Infection may trigger some cases of myasthenia gravis. When activated, the immune system may mistake portions of the acetylcholine receptor for portions of an invading virus, though no candidate virus has yet been identified conclusively. About 10% of those with myasthenia gravis also have thymomas, or benign tumors of the thymus gland. The thymus is a principal organ of the immune system, and researchers speculate that thymic irregularities are involved in the progression of myasthenia gravis.

In myasthenia gravis, antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction which prevents the muscle contraction from occurring. These antibodies are produced by the body's own immune system. Thus, myasthenia gravis is an autoimmune disease because the immune system - which normally protects the body from foreign organisms - mistakenly attacks itself.

More information on myasthenia gravis

What is myasthenia gravis? - Myasthenia gravis is a disorder of neuromuscular function due to the presence of antibodies to acetylcholine receptors at the neuromuscular junction.
What causes myasthenia gravis? - Myasthenia gravis is caused by a defect in the transmission of nerve impulses to muscles. Deficiency of acetylcholine at the neuromuscular junctions causes myasthenia gravis.
What're the risk factors for myasthenia gravis? - Myasthenia gravis commonly affects young adult women and older men. Myasthenia gravis may be associated with other autoimmune diseases.
What's the role of the thymus gland? - The thymus gland plays an important role in the development of the immune system in early life. In most adults with myasthenia gravis, the thymus gland is abnormal.
What're the signs and symptoms of myasthenia gravis? - Symptoms of myasthenia gravis include fatigue and exhaustion of the muscular system with a tendency to fluctuate in severity without sensory disturbance or atrophy.
How is myasthenia gravis diagnosed? - Myasthenia gravis is often diagnosed accurately by a careful medical history and a neuromuscular exam, but several tests are used to confirm the diagnosis.
What's the treatment for myasthenia gravis? - The treatment of myasthenia gravis depends on several factors, including age, overall health, severity of disease, and rate of disease progression.
What's a myasthenic crisis? - A myasthenic crisis occurs when weakness affects the muscles that control breathing. Plasma exchange may be performed to treat myasthenic crisis.
Does myasthenia gravis affect pregnancy? - Pregnant women with myasthenia gravis often have more weakness and fatigue because of the added weight and effort of pregnancy.
What's the prognosis of myasthenia gravis? - Myasthenia gravis is a chronic disease. With treatment, patients with myasthenia gravis will have significant improvement of their muscle weakness.
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