Myasthenia gravis is an autoimmune disorder characterized by muscle weakness. The disease tends to strike women more often than men (ratio of about 3 to 2, respectively), usually affecting women between the ages of 20 and 40 (Beers 2005). After about age 50, both sexes tend to be equally affected (Phillips 1994).
Myasthenia gravis is progressive and can affect any muscle group; however, people afflicted with the disease often have weakness of face, tongue, and neck. This muscle weakness might result in double vision or drooping eyelids, which along with difficulty chewing, swallowing, and talking, are characteristic symptoms of myasthenia gravis.