Myasthenia gravis is an autoimmune disease that affects the contact point between nerves and muscles. For some unknown reason, the body's immune system, which normally helps fight infections, attacks the acetylcholine receptors found on muscles.
These receptors normally receive a chemical called acetylcholine, which is released by the nerves at the neuromuscular junction (the point of contact between nerve and muscle) and signals the muscles to contract. Once these receptors are damaged or processes involved with the receptors are altered, the muscles cannot respond to the nerve signals and the muscles become weak.
Myasthenia gravis is almost twice as common in women as in men. It is most commonly diagnosed in women under 40 and men over 50 but it can occur at any age. Children are very unlikely to suffer from this disease. People from all continents are equally susceptible.
A closely related disease called congenital myasthenic syndrome is genetically inherited. Myasthenia gravis itself probably has a genetic component, but the children of people with this condition are only slightly more likely than average to suffer from autoimmune disease.
Myasthenia gravis is a serious condition, but not usually life-threatening. Most people with myasthenia gravis have a life expectancy that is the same as for someone without it. People affected with myasthenia gravis have reduced physical activities, reduced quality of life, and spend more days being sick. In severe cases, the chest muscles can become so weak that patients have trouble breathing on their own and may require a ventilator for a few days to a few weeks.