Dermatomyositis is a rare autoimmune disease that can cause damage to various internal organs and can only affect the skin or muscles. Its main features include unique skin lesions such as edematous purplish red spots, purplish red papules on the extended side of the finger joint (i.e. one side of the back of the hand), and skin discoloration, as well as muscle weakness. Dermatomyositis can occur in any age group, with two peaks of onset: childhood and 40-60 years old. According to clinical manifestations, dermatomyositis can be divided into the following types: polymyositis, adult dermatomyositis, dermatomyositis or polymyositis with malignant tumors, pediatric dermatomyositis, dermatomyositis or polymyositis with other connective tissue diseases (such as overlap syndrome), and myopathic dermatomyositis. Among them, polymyositis is mainly seen in adults, rare in children, and more in females than males. There are several common causes of dermatomyositis, including four common causes. 1. Abnormal autoimmune system. The immune system recognizes errors and attacks normal skin and muscle tissue. 2. Infection. Children with dermatomyositis often have a history of upper respiratory tract infection before onset, and some patients may be related to EB virus or small RNA virus infection. 3. Malignant tumors. Dermatomyositis can be combined with malignant tumors, such as nasopharyngeal carcinoma, breast cancer, ovarian cancer, lung cancer, stomach cancer, etc. 4. Genetics. Dermatomyositis has a certain degree of familial inheritance, and if someone in the family suffers from dermatomyositis, the probability of individual illness will be relatively high. The main symptoms of dermatomyositis are skin damage and muscle damage. ★ Skin damage 1. Purple red spots on the eyelids. Edematous purplish red patches centered on the upper eyelids can affect the "V" - shaped area of the forehead, scalp, cheeks, and chest, with high diagnostic specificity. 2. Gottlong papules. Flat purplish red papules on the extended side of the finger joint and metacarpophalangeal joint, mostly symmetrically distributed, with bran like scales attached to the surface. After the skin lesion subsides, skin atrophy, capillary dilation, and decreased pigmentation may remain. 3. Skin discoloration. On the basis of erythema and scales, the face, neck, and upper chest gradually show brown pigmentation, punctate depigmentation, punctate keratinization, mild skin atrophy, and capillary dilation. Patients with muscle damage often exhibit symmetrical muscle weakness, pain, and tenderness. The most common muscle groups invaded by dermatomyositis are the proximal limb muscle group, scapular girdle muscle group, neck and throat muscle group. Patients may experience difficulties in raising their hands, squatting, going upstairs, lifting their head, and swallowing. During the acute phase, affected muscles may experience swelling, and in severe cases, they may become bedridden with complete loss of autonomous movement. What should patients pay attention to? They need to pay attention to sun protection. Because skin damage is more sensitive to sunlight, it is important to wear sun protection clothing or apply sunscreen when going out. Passive training should be performed on the affected limb to prevent muscle atrophy. Under the guidance of a physical therapist, engage in moderate exercise to maintain and improve muscle strength and flexibility. It is advisable to eat foods high in vitamins and protein. If the chewing and swallowing function is gradually impaired, it is necessary to adjust the dietary structure and focus on foods that are easy to swallow. It is necessary to observe the extent of skin damage, color changes, muscle weakness, and degree of muscle pain in daily life. Regularly perform serum muscle enzyme profiling, such as testing for serum myoglobin and creatine. How to recognize early signals in patients with dermatomyositis? The main focus in the early stages is on the skin