Juvenile dermatomyositis (JDM) is an important subtype of dermatomyositis characterized by inflammation of muscle, skin and gastrointestinal tract. A 14-year-old girl, with a history of fever, joint pain, easy fatigability and a rash since the age of 3 years is described. Physical examination, laboratory evaluation, electromyography (EMG) and muscle biopsy were suggestive of a chronic inflammatory process involving the muscles, most likely dermatomyositis. The report highlights the importance of a muscle biopsy as the gold standard for diagnosing dermatomyositis.