Muscle weakness is mainly manifested as partial or systemic skeletal muscle weakness, easy fatigue, aggravated symptoms after exercise, relieved symptoms after rest, generally serious illness, long course of disease, and refractory. It can occur at all ages, mostly in 15 ~ 35 years old, and the incidence ratio of male to female is about 1:2.5. The onset is urgent and slow, and it is often hidden. Symptoms can be temporarily relieved, alleviated, relapsed and aggravated, often appearing alternately, and can be partially recovered after rest and anticholinesterase drug treatment. Childhood myasthenia gravis refers to the onset from newborn to adolescence. Except for a few cases of generalized myasthenia gravis, most of them are confined to extraocular muscles.