Myasthenia Gravis
Source: MedlinePlus Health Topics, U.S. National Library of Medicine
What is myasthenia gravis? Myasthenia gravis, sometimes called MG, is a chronic (long-lasting) disease that causes weakness in your voluntary muscles. The voluntary muscles are the ones that you can control. They include the muscles you use for: Eye and eyelid movement Facial expressions Chewing Talking Swallowing Breathing Moving your arms and legs You can also have weakness in other muscles. This weakness gets worse with activity, and better with rest. Myasthenia gravis is a type of autoimmune disease. In autoimmune diseases , your immune system attacks the healthy cells of your organs and tissues by mistake. What causes myasthenia gravis? Myasthenia gravis is caused by an error in how nerve signals are sent to muscles. These signals get blocked at the nerve-muscle junction. This junction is the place where the nerve endings connect with the muscles they control. Normally, this is how the signals work: The signals travel down a nerve that controls movement in the muscle The nerve endings release a substance called acetylcholine Acetylcholine binds to the muscle tissue at the nerve-muscle junction This causes the muscle to contract (move) But in someone with myasthenia gravis, the body's own immune system makes antibodies that block the binding of acetylcholine to the muscle. This makes the muscles weaker. The thymus gland, which is part of your immune system, may play a role in myasthenia gravis. Normally, your thymus gland is active and growing when you are a child. It makes white blood cells to fight infections. At puberty, it starts getting smaller and is replaced by fat. It is usually small by the time you are an adult. But in many adults with myasthenia gravis, the thymus gland stays large. And some people with myasthenia gravis can get thymomas, which are tumors of the thymus. The are usually benign (not cancer), but they can sometimes become cancerous . Who is more likely to develop myasthenia gravis? Although myasthenia gravis can affect people of any age,