Myasthenia gravis has a prevalence of 0.5-5/100,000 in the general population and can occur at any age, but is predominant in young women and older men. The first peak is at the age of 20, the second peak is about 50, and the ratio of men to women is 1:2, while in young patients this ratio reaches 1:4. Transverse muscle weakness, fatigue, lightness in the morning and heaviness in the evening, aggravated by activity and reduced by rest are the main symptoms of this disease. Myasthenia gravis attacks have daily or even hourly ups and downs. Myasthenia gravis can come on gradually or rapidly, and can be fully recovered or partially recovered. The muscle weakness of the extremities is mostly symmetrical, with the proximal muscle groups being heavier than the distal ones and the upper extremities heavier than the legs. Individual patients have symptoms of muscle weakness with single muscle asymmetry. Deep tendon reflexes are present, but may disappear temporarily with repeated stimulation. Patients often complain of nonspecific sensation but have normal sensation on examination. Autonomic nervous system changes manifest as pupillary changes, bladder weakness and hyperhidrosis but the above symptoms are uncommon. Occasionally found with cone fasciculation signs, manifesting as hyperactive tendon reflexes in the extremities, which can cause pathological reflexes. Mental stress, symptoms come on suddenly or gradually. Myasthenia gravis manifests as intractable muscle weakness after anesthesia or the use of muscle relaxants. Internationally, a modified Osserman typing is usually used as follows: Type I: signs and symptoms of ocular muscles only, no mortality. Type IIA: Mild generalized muscle weakness with slow onset, often involving the ocular muscles, gradually affecting the myelinated and medullary muscles. No respiratory distress, poor response to drugs. Activity is limited and mortality is minimal. IIB: Moderate generalized muscle weakness involving the medullary muscles, with good respiration and poor response to drugs. Activity is limited and mortality is low. Type III: acute fulminant attacks, early involvement of respiratory muscles, severe damage to the medulla oblongata and myelomeningocele, and the highest detection rate of thymoma. Activity is limited and poorly responsive to medication, but mortality is low. Type IV: late severe generalized myasthenia gravis. It reaches this level at least 2 years after the onset of type I or II symptoms and can occur gradually or suddenly. Thymoma is found at the 2nd highest rate. Poor response to medications and poor prognosis. Myasthenia gravis has different clinical symptoms at various ages: Juvenile myasthenia 4 % of all myasthenia cases develop before the age of 10 years and 24 % of cases have an attack before the age of 20 years, with a female predominance (4:1). This type, in contrast to the infantile type, has a relatively small genetic component, and it is mainly the immune mechanism that plays a role in the pathogenesis. The course of the disease is slow to progress with marked ups and downs. Thymoma is rare. Adult myasthenia gravis 75% of adult myasthenia gravis cases have thymic hyperplasia, which is more common in young adults; 10-15% of cases have thymoma, which is common in the elderly. Male patients have a faster onset, lower remission rate and higher mortality than females. The clinical course has a distinct exacerbation and remission phase. Patients with 3/4 ocular muscle involvement develop generalized myasthenia in the first 3 years, with damage to the pharyngeal muscles and, in the most severe cases, an asymmetric combination of symptoms with multiple muscle groups involved. The majority of patients who survive become chronically migrated, with fewer episodes and reduced symptoms.