I believe that many patients do not know what myositis and dermatomyositis are exactly one disease. Here is a general introduction to the two diseases. Polymyositis and dermatomyositis are a group of immune diseases caused by immune disorders, mainly involving the muscles of the extremities. They manifest as muscle weakness in the proximal extremities over a period of weeks to months, and are often accompanied by systemic manifestations such as weakness, anorexia, weight loss, and fever. Skeletal muscle involvement Symmetrical proximal muscle weakness is a characteristic manifestation of the disease, involving the muscles of the upper extremities, which may result in inability to lift the hands, comb the hair, dress and bathe oneself. If the muscles of the lower extremities are involved, it may be difficult to go up and down stairs or to stand up after sitting down. Some patients have neck weakness, which is manifested by difficulty in raising the head when lying down, and the head is often tilted back. Manifestations of skin involvement In addition to muscle involvement, patients with dermatomyositis have characteristic manifestations of skin involvement. Common skin lesions include:j Periocular rash (heliotroperash): This is a characteristic skin lesion of dermatomyositis and presents as an edematous purplish rash on the upper eyelid or around the orbit, either unilaterally or bilaterally, aggravated by light. This rash may also appear on both cheeks, the bridge of the nose, the neck, the V-shaped area of the anterior chest, and the back of the shoulders (called the shawl sign). kGottron rash: a red or purplish maculopapular rash appearing on the extensor surfaces of joints, especially the metacarpophalangeal, interphalangeal, or elbow joints, with irregular margins or fused into patches, often accompanied by skin atrophy, capillary dilation, and hyperpigmentation or hypopigmentation. lPerineal lesions: at the nail root crease Capillary dilated erythema or petechiae may be seen, with irregular thickening of the nail crease and nail bed, and localized hyperpigmentation or depigmentation. “Mechanic’s hand”: hyperkeratosis, cracks and roughness of the skin on the palm and lateral surfaces of the fingers, resembling the hands of skilled individuals who have been engaged in manual work for a long time, hence the name “mechanic’s hand”. Pulmonary involvement: Interstitial pneumonia, pulmonary fibrosis, and pleurisy are the most common pulmonary manifestations of myositis and dermatomyositis, and can occur at any time during the course of the disease. They manifest as chest tightness, shortness of breath, cough, sputum, dyspnea, and cyanosis. 2. Gastrointestinal tract involvement: myositis and dermatomyositis involving the pharynx and upper transverse esophagus are more common and manifest as dysphagia, choking and coughing when drinking, and fluid flow from the nostrils. Weak and dilated peristalsis of the lower esophagus and small intestine can cause acid reflux, esophagitis, dysphagia, epigastric distention and absorption disorders. Of course, some patients may also present with heart, kidney and joint involvement. When the above symptoms appear, it is necessary to consider the possibility of myositis and dermatomyositis, and it is recommended to go to the rheumatology department of a large local hospital for a clear diagnosis and further standardized treatment. In terms of treatment, there are many immunosuppressive drugs that can effectively control the disease, but a rheumatologist needs to reasonably match the drugs to effectively control the disease without toxicity or side effects. Therefore, once the diagnosis is confirmed, patients need to adhere to regular medication and gradually adjust the drugs, myositis and dermatomyositis can be effectively controlled and completely relieved.