Poor esophageal motility, dilatation and retention of barium in the pyriform fossa are the digestive symptoms of dermatomyositis and polymyositis, which are currently considered to be autoimmune diseases, PM has no skin damage, and the etiology and pathogenesis of DM and PM are still unknown. Poor peristaltic dilatation of the esophagus and retention of barium in the pyriform fossa may be related to the following factors: 1. Infection: A variety of infections (bacterial, viral, protozoan, etc.) have been found to be associated with this disease. The more certain is JDM, before the onset of the upper respiratory tract infection, anti-streptococcal “O” value is elevated, so it is thought to be related to bacterial infection after the metabolic reaction. A variety of virus-like particles were found in the nuclei of myocytes, the cytoplasm and nuclei of vascular endothelial cells, perivascular histiocytes and fibroblasts, and elevated antibodies to viruses, especially paramyxoviruses, were detected in the serum of some patients. The Jo-1 (histidyl-tRNA synthetase) antigen is unique to PM, and the Jo-1 antigen is similar in protein sequence to some viral antigens, so whether it has a “molecular mimicry” effect needs to be further investigated. 2, tumor: the disease is associated with a high incidence of malignant tumors, especially DM, some reports up to 43%. Removal of the tumor lesion can make the disease remit, and the intradermal test with the patient’s tumor raised fluid was positive, and the passive metastasis test was also positive. Antibodies against the tumor were found in the patient’s serum. There is cross-antigenicity between the tumor tissue and the normal muscle fibers, tendon sheaths, blood vessels, and connective tissues of the body, and these normal tissues can also react as antigens with anti-tumor antibodies, causing lesions in these tissues. However, there is also a contrary view that the incidence of DM/PM patients with malignant tumors is not significantly higher compared to the normal population. 3. Immunity: Although the lesioned organs of DM and PM are mainly muscles, it is not known so far what are the muscle-specific autoantigens.