What is the pathology that causes myasthenia gravis?

Autoantibodies...: Myasthenia gravis is characterized by weakness / fatigue of muscles under voluntary control. It is caused by abnormal communication between nerves and muscles. In mg, the immune system makes autoantibodies that block or destroy many of a muscles' receptor sites for a neurotransmitter called acetylcholine. With fewer receptor sites, your muscles receive fewer nerve signals resulting in weakness.