Causes of Myasthenia Gravis
In myasthenia gravis, antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction. This prevents the muscle contraction from occurring. Myasthenia gravis is considered an autoimmune disease, in which the body's immune system turns against itself and attacks its own tissues. Research scientists are still trying to understand why the immune system attacks the acetylcholine receptors.
Myasthenia Gravis and Who It Affects
It is estimated that the number of people who are affected by myasthenia gravis is between 5 to 14 people out of 100,000. Myasthenia gravis occurs in men and women of all ethnic groups, and although myasthenia gravis most commonly affects women under 40 and men over 60, it can occur at any age.
Myasthenia gravis is not directly inherited, nor is it contagious. However, if a woman with myasthenia gravis becomes pregnant, the baby may acquire antibodies from the mother and have
myasthenia gravis symptoms for a few weeks or months after birth. This is called neonatal myasthenia. In rare cases, myasthenia gravis is caused by a defective gene and appears in infants born to mothers who do not have myasthenia gravis. This type of myasthenia gravis is called congenital myasthenia.
Myasthenia Gravis and the Thymus Gland
The thymus gland, which is found in the upper chest area beneath the breastbone, is a part of the body's normal immune system. The thymus gland is abnormal in most adults with myasthenia gravis. Some people with myasthenia gravis develop thymomas, which are tumors of the thymus gland. Generally, thymomas are benign, but they can become malignant (cancerous). The relationship between the thymus gland and myasthenia gravis is not yet fully understood.
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