Myositis, a group of autoimmune diseases mainly characterized by muscle weakness and muscle inflammation, includes dermatomyositis, polymyositis, inclusion body myositis and childhood dermatomyositis, etc. The clinical manifestations, treatment and prognosis of different subtypes vary greatly. There is no data on the average survival rate of myositis patients in China, but myositis is one of the more dangerous diseases among rheumatic diseases because it can be combined with important organ damage and malignant tumors. Available research data show that most patients with dermatomyositis and polymyositis respond well to glucocorticoid therapy, and with systematic and standardized glucocorticoid therapy, combined with immunosuppressive drugs, the disease can be effectively controlled and the survival rate is high. However, for patients of advanced age, patients with important organ complications such as lung and heart and malignant tumors, their conditions are more critical and prone to co-infection, with a certain mortality rate and poor prognosis. In addition, some patients may be controlled or fear the adverse effects of treatment drugs, reduce or stop their own drugs, resulting in relapse of the disease. These patients are often prone to multiple organ damage after relapse and have a poor prognosis if they are not treated actively. Therefore, for patients with myositis, early diagnosis, systematic and standardized treatment is the key to keep the disease stable and improve survival rates.