DefinitionMyasthenia gravis is a neuromuscular disorder. Neuromuscular disorders involve the muscles and the nerves that control them.Alternative NamesNeuromusclar disorder - myasthenia gravis Causes, incidence, and risk factorsMyasthenia gravis causes weakness of the voluntary (skeletal) muscles. These are the muscles that create movement and are normally under your conscious control. The involuntary muscles, on the other hand, are not under conscious control (such as the muscles of your heart and many other internal organs).In myasthenia gravis, weakness occurs because the nerve that activates a particular muscle does a poor job of stimulating that muscle. This problem occurs because immune cells (which normally attack foreign invaders) target and attack the body's own healthy cells. Thi