Dermatomyositis is a life-threatening inflammatory connective tissue disease involving mainly skin and muscle, with muscle involvement without skin involvement called “polymyositis” or “polymyositis”; it is a category of autoimmune diseases. In addition to skin and muscle involvement, the disease can also involve other organs, especially the lungs, especially the acute form of interstitial lung disease is the most important cause of death in a short period of time. The etiology of the disease is unclear, with approximately 1/3 of adult dermatomyositis associated with malignancy and childhood dermatomyositis or polymyositis often triggered by infection. The disease can develop in all age groups, but it is most common between 40 and 60 years old, and the ratio of male to female prevalence is about 1:2. Because the disease is not a common disease, it is often not diagnosed early and the best time for treatment is lost, causing difficulties in treatment; and because the process of the disease is long, it does not work in the short term and has a high recurrence rate, so it is important to adhere to long-term, regular and reasonable treatment to achieve the best results and even complete recovery. The first thing you should do is to cooperate with your physician to carefully evaluate the organs involved in the disease; carefully look for the cause of the disease, especially if there is a malignant tumor. 2. Glucocorticoids are still effective and low-cost drugs for the treatment of the disease, and must be applied under the guidance of physicians. 3, although the disease has a high mortality rate, most patients can recover; the course of treatment is long, generally needing more than two years. 4.It is advisable to choose a diet with high protein, high vitamin, low salt and low fat; prevent colds, maintain optimism, live a regular life and avoid strain. 5, muscle strength should be gradually restored after the exercise, to walk on flat ground, do not be too hasty. 6.People with heavy skin damage should avoid sun exposure, wear a hat or umbrella and long-sleeved clothes when going out. 7. Regular outpatient follow-up, adjust the dosage and type of medication.