The common clinical manifestation of dermatomyositis is muscle weakness, accompanied by muscle pain, which may cause movement disorders and limitation of movement as the disease progresses. Usually, dermatomyositis is characterized by skin damage and the appearance of purplish-red patches of skin with marked edema. The skin on both eyelids first begins to discolor with purplish-red edematous patches but does not interfere with daily movement of the eyes. Skin manifestations are common on the extended surfaces of the metacarpophalangeal joints, elbows, knees, and straddles, as well as on the shoulders and areas prone to friction. It is accompanied by muscle pain, motor dysfunction, joint pain, physical weakness, and eyelid swelling, and muscle involvement is usually bilateral and symmetrical. In the case of cervical flexors, it is difficult to raise the head in a horizontal position, and in a sitting position, there is no ability to tilt the head. If the pharyngeal muscles are involved, there may be difficulty in swallowing, hoarseness, and difficulty in pronunciation, etc. If fluid food is ingested, it may flow out through the nostrils and cause choking and coughing. Heart involvement is relatively mild, such as causing heart rhythm disturbance, palpitations, and arrhythmia. If it progresses to advanced stages, it can lead to congestive heart failure due to myocarditis or myocardial fibrosis. Dermatomyositis should be treated in a timely manner. Depending on the development of the disease and the treatment measures taken, most patients can be relieved or even cured, and a small percentage can show signs of muscle weakness. According to statistics, a significant percentage of patients with dermatomyositis develop concomitant malignant tumors, especially visceral tumors, therefore, patients with dermatomyositis must have a tumor examination or whole-body PET CT during routine examinations to exclude concomitant tumors.