Juvenile dermatomyositis is a rare multi-system auto-immune disease, particularly causing inflammation of skin and muscles of children. The diagnosis is based on the clinical picture with typical cutaneous lesions, which frequently are the first signs of the disease in contrast to muscle involvement. Muscular MRI is nowadays the first line investigation to diagnose myositis. Recently specific auto-antibodies have been detected allowing a better understanding of the disease and being important prognostic factors. An early diagnosis and aggressive treatment is crucial to induce remission of the disease, especially restore muscular function and to prevent severe complications such as calcinosis and lipodystrophy, which are difficult to treat as well as vital organ dysfunction.