Dermatomyositis is a disease with muscle inflammation accompanied or not by skin lesions. Polymyositis is an autoimmune disease and responds to immunosuppressive drugs. The disease can appear at any age, usually in adolescence (10-15 years old) and middle age (45-60 years old), women are more affected than men. The incidence of polymyositis in the community is estimated at 5-10 cases/1 million people.

Idiopathic inflammatory myopathies are a group of chronic autoimmune diseases that primarily affect the proximal muscles. Of these, inclusion body myositis is the most common form. Inclusion body myositis is an idiopathic, slowly progressive inflammatory myopathy that typically occurs in middle-aged men.

Inflammatory myopathies is a less common autoimmune disease than systemic lupus erythematosus, scleroderma, and polyarteritis nodosa. Typical symptoms of the disease are dermatitis, myositis, and muscle weakness. The disease usually appears in middle-aged people between 40 and 60 years old. However, children under 10 years old can also have inflammatory myopathies.