Myasthenia gravis is a chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles. It occurs when communication between the nerve and muscle is interrupted at the neuromuscular junction, the place where nerve cells connect with the muscles they control. The specific cause of abnormal autoimmune responses in patients with myasthenia gravis is unknown, but it is believed to be caused by an abnormal immune reaction in which the bodys immune defenses inappropriately attack certain proteins in muscles that receive nerve impulses. Factors that can trigger or worsen myasthenia gravis include infection, stress, surgery, or an adverse reaction to medication. There is no cure for myasthenia gravis, but treatment can help with symptoms.