What causes myasthenia gravis is a breakdown in the communication between nerve impulses and muscles. The condition arises when the body’s immune system blocks or destroys muscle receptor sites for acetylcholine, a neurotransmitter that delivers instructions for the muscle to contract. Antibodies, that normally defend the body from infection, instead attack the neuromuscular junction where nerve cells and muscle tissue join, disrupting nerve impulses.
Doctors also believe the thymus gland plays a role in myasthenia gravis that is not yet completely understood. In early life, the gland contributes to the development of the immune system that shrinks with age eventually replaced by fat. Adults with myasthenia gravis have an enlarged thymus gland with indications of an immune system problem. It is possible that the thymus gland causes myasthenia gravis by issuing distorted instructions to immune cells, leading to the production of antibodies that damage the acetylcholine receptors.