The clinical etiology of dermatomyositis is not clear, mostly related to viral infection, immune abnormality, heredity and tumor. 1. Viral infection: studies have proved that patients with genetic susceptibility are susceptible to immune-mediated dermatomyositis after viral infection, and most patients have a history of influenza viruses A and B, coxsackie viruses, and other infections prior to the disease. 2. Immune abnormality: if the patient has autoantibody production, inflammatory cell infiltration, will mediate the immunogenic reaction, for patients with genetic susceptibility, it is easy to induce into dermatomyositis. 3. Heredity: patients with family heredity are more likely to suffer from the disease; the occurrence of the disease may be related to certain susceptibility genes. 4. Tumors: Studies have shown that patients who are genetically susceptible to the disease are susceptible to dermatomyositis when they have tumors. When patients suffer from dermatomyositis, it is recommended to go to the hospital immediately to clarify the cause of the disease, and under the guidance of specialists to carry out treatment.