Myasthenia gravis is a neuromuscular disease which affects the muscles and the nerves that control them. It is characterized by weakness and fatigability of skeletal muscles. Myasthenia gravis is an autoimmune disorder in which immune cells, which normally attack foreign microorganisms, target and attack the body's own healthy cells instead. Thus, the autoimmune response produces antibodies that block the muscle cells from receiving nerve impulses from neurons (nerve cells) necessary for the contraction of the muscle fibers. In other words, myasthenia gravis occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control. Normally when impulses travel down the nerve, the nerve endings release a neurotransmitter called acetylcholine. Acetylcholine travels from the neuromuscular junction and binds to acetylcholine receptors which are activated and generate a muscle contraction.
The cause of myasthenia gravis, as well as others autoimmune diseases, is unknown. In some cases, myasthenia gravis may be associated with tumors of the thymus (an organ of the immune system). Patients with myasthenia gravis have a higher risk of having other autoimmune disorders, such as thyrotoxicosis, rheumatoid arthritis, and systemic lupus erythematosus (lupus). Myasthenia gravis can affect people at any age. It is most common in young women and older men. There is no cure for myasthenia gravis, but treatment can help relieve signs and symptoms — such as weakness of arm or leg muscles, double vision, drooping eyelids, and difficulties with speech, chewing, swallowing and breathing. While myasthenia gravis can affect people of any age, it's more common in women younger than 40 and in men older than 60.
Myasthenia Gravis (Video)