Many people think that dermatomyositis and polymyositis are one skin disease, but this is not true. Like SLE, this disease is an autoimmune disease with multi-tissue, multi-organ and multi-system damage. Western medicine refers to those with skin damage as “dermatomyositis” and those without skin damage as “polymyositis”. The incidence in China is about 2 in 10,000; males account for 20% and females for 80%; the disease can develop at any age, and is more common at ages 5-15 and 40-60. The main pathological changes are extensive muscle fiber degeneration and chronic inflammatory cell infiltration. Interstitial myositis is associated with swelling or atrophy of muscle fibers. Laboratory tests reveal electromyographic changes as well as elevated serum glutamate transaminase, creatine phosphokinase and lactate dehydrogenase, and serum rheumatoid factor and antinuclear antibodies are positive in approximately 60% or more of patients, but not in high titers. The clinical manifestations of dermatomyositis and polymyositis are as follows 1. Muscle symptoms: symmetrical, progressive muscle weakness in the proximal extremities, especially in the pelvic girdle and thigh muscles, difficulty in walking up and down stairs, squatting or rising, and walking; inability to comb the head or lift objects when the shoulder and arm muscles are damaged, or inability to lift both arms; drooping of the human head when the neck muscles are damaged; difficulty in swallowing when the throat and esophageal muscles are damaged; difficulty in swallowing when the vocal cord muscles are damaged Hoarseness. These symptoms are similar to those of myasthenia gravis, except that polymyositis is rare in which the respiratory and ophthalmic muscles are damaged and the tendon reflexes are normal. Instead, there is spontaneous muscle pain or muscle tenderness and grip pain. 2. Skin symptoms: About 40% of patients have purple erythema in the skin around the eyelids, nose, cheeks, forehead and nails. In addition, red rashes can be seen on the chest and the backs of the joints on the extremities. Some rashes may have persistent itching, and there are varying degrees of capillary dilation, pigment loss or hyperpigmentation, and a few pediatric patients have skin calcifications. In patients with fulminant forms, orbital and periorbital edema can be seen. 3. Cardiac and pulmonary symptoms: inflammation or necrosis of myocardial fibers, about 25% of patients may have abnormal ECG, about 5% of patients have heart failure, and more than 60% of those who die have myocardial damage. About 10% of cases have interstitial pulmonary fibrosis, so there is cough and dyspnea, due to respiratory dysfunction, coupled with myocardial damage and decreased body resistance, susceptible to microbial infection, often leading to aspiration pneumonia, life-threatening. 4, kidney damage: about 25% of patients have kidney damage after high fever due to infection, mainly interstitial nephritis, which can lead to renal failure due to repeated infection (cold) producing myoglobulinuria and increased urinary creatine, often life-threatening. 5, joint symptoms: about 30% of patients have joint pain and morning stiffness; about 20% of patients have Raynaud’s phenomenon such as purple, numbness and pain when the palm and fingers are cold.