Osserman classified adult myasthenia gravis into five types according to age of onset, degree and extent of muscle weakness involvement and severity of disease: Type I: simple ocular muscle type, limited to simple ocular muscle paralysis. Type IIa: mild generalized muscle weakness with cranial nerve (extraocular muscles), limb and trunk muscle weakness, but does not affect respiratory muscles, no obvious medullary muscle symptoms, this group of patients respond well to anticholinesterase drugs and have low mortality. Type IIb: there are obvious face droop, diplopia, dysarthria and dysphagia and cervical and limb muscle weakness, some patients have good trunk muscle and limb muscle strength, this group of patients are often insensitive to anticholinesterase drugs, prone to myasthenia gravis crisis, mortality rate is also relatively high, should be paid attention to. Type III: Acute progressive type, often with sudden onset and rapid progression within 6 months, with early respiratory muscle involvement and severe involvement of the medullary, extremity and trunk muscles, with poor response to anticholinesterase drugs, prone to myasthenia gravis and high mortality. It is often associated with thymoma. It is a clinical priority for management. Type IV: Late onset generalized weakness. The symptoms are often aggravated after several years of type I and IIa, with more pronounced generalized muscle weakness, mostly accompanied by thymoma.