The symptoms of myasthenia gravis vary depending on the muscles involved. First, eye muscle involvement, it will cause some eye symptoms, such as eyelid drooping, narrow lid fissure, some patients even feel unable to open their eyes, and diplopia, etc. Second, throat muscle involvement, throat muscle involvement patients appear swallowing difficulties, hoarse voice, low voice, serious patients can not eat, need to insert a gastric tube. Third, facial muscle involvement, which can be manifested as a dull and numb facial expression, or even no expression, some patients smile more than crying, also known as a bitter smile. Fourth, the shoulder muscles are involved, which can be manifested as the inability to lift the neck and the inability to swing the neck normally. Fifth, the involvement of the limbs, such as the inability to lift the hands and walk.