Dermatomyositis (DM) is a long-term inflammatory autoimmune disorder which affects the skin and the muscles. Its symptoms are generally a skin rash and worsening muscle weakness over time. These may occur suddenly or develop over months. Other symptoms may include weight loss, fever, lung inflammation, or light sensitivity. Complications may include calcium deposits in muscles or skin.
Dermatomyositis is an autoimmune disorder featuring both humoral and T-cell autoimmune processes. Dermatomyositis may develop as a paraneoplastic syndrome associated with several forms of malignancy. It is known to be associated with several viruses, especially coxsackievirus, but no definitive causal link has been found. Dermatomyositis is considered a type of inflammatory myopathy. Diagnosis is typically based on some combination of symptoms, blood tests, electromyography, and muscle biopsies. Eighty percent of adults and sixty percent of children with juvenile dermatomyositis have a myositis-specific antibody (MSA).