• Dermatology
• Magnetic Resonance Imaging
• Paediatrics
• Rheumatology

A 4-year-old girl presented with a 2-year history of rashes on both hands, trunk and knees and an inability to move the right knee with difficulty in walking. On examination, multiple hypopigmented confluent macules were present on the trunk (figure 1A), extensor surfaces of knees (figure 1B), on elbows (figure 1C) and dorsal surface of bilateral metacarpophalangeal and interphalangeal joints (figure 1D). The bulk of the right thigh and calf was increased compared with the left side and reflexes were 2+ throughout. Blood tests revealed an elevated level of creatine kinase (CK) (320 U/L), erythrocyte sedimentation rate was raised (30 mm/hour) and C reactive protein (CRP) was elevated. Total leucocyte count was also elevated (18 000/mm³). An MRI of the knee (figure 2) showed diffuse subcutaneous oedema with ill-defined T2/short tau inversion recovery (STIR) hyperintensity in the right leg muscles with increased bulk (figure 2C). A skin biopsy was performed (near the right knee) which showed multifocal inflammatory infiltrates in a perivascular distribution. Juvenile dermatomyositis was suspected.