[Juvenile dermatomyositis--acute recidivism or sepsis?]

A 22-year-old male with juvenile dermatomyositis presented with fever up to 40 degrees C and acute pain in his right thigh accompanied by muscle weakness, a skin rash and a tender swelling. Serum aspartate aminotransferase (AST) and aldolase were mildly elevated. C-reactive protein (CRP) and fibrinogen were markedly increased. The differential white blood cell count revealed relative lymphopenia. Radiography showed diffuse calcifications particularly around the thighs and knees of both legs. Magnetic resonance imaging (MRI) demonstrated inflammatory infiltrates in the right thigh. The lesions were identified as phlegmone by immunoszintigraphy with 99mTc-labelled antigranulocyte antibodies. On the 10th day of treatment Staphylococcus aureus was cultured from blood. Patients with juvenile dermatomyositis and calcinosis may develop bacterial infections of soft tissue which sometimes mimic a disease flare. For differential diagnosis plain radiographs, CT scans and MRI are of limited value. Immunoszintigraphy is able to differentiate between infiltrates caused by granulocytes and lymphocytes.