Myasthenia Gravis:

Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by varying degrees of weakness of the skeletal muscles of the body. Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often, but not always, involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.

Myasthenia gravis can affect people of any age, but it's more common in women younger than 40 or older than 70, and in men older than 50. There's no cure for myasthenia gravis, but treatments are available to help control the signs and symptoms of the condition.