an autoimmune disorder (see autoimmunity) in which the body produces antibodies against acetylcholine receptors, causing faulty transmission of nerve impulses at neuromuscular junctions. Affected muscles—initially those of the face and neck—are easily fatigued and may become paralyzed temporarily (e.g., muscles involved in eating may fail to function normally toward the end of a meal, speech may become slurred after a period of talking). The disease is progressive, eventually affecting muscles throughout the body.