This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
Cause of myasthenia gravis 
Select and explain. 
A. Decreased release of Ach at NM junction, B. Loss of muscles fibers, C. Destruction of receptors by antibody, D. Destruction of receptors by autolysis
C: Destruction of receptors by antibody
Answer: C: Destruction of receptors by antibody 
Explanation: Myasthenia gravis is rare autoimmune disease caused by the formation of circulating antibodies to the nicotinic A-ch receptors. These antibodies destroy some of the receptors and bind others to neighboring receptors. The disease is characterized by rapid onset of fatigue with marked generalized weakness of muscles. The most commonly affected muscles are: extraocular muscles, facial, swallowing and mastication muscles.Ref: Textbook of physiology, Dir. Prof. AK Jain, 5th edition.