[Pigmented villonodular synovitis with polyarticular presentation].

Pigmented villonodular synovitis (PSV) rarely involves more than one joint, and its occurrence in children is uncommon. One case of PSV with polyarticular involvement in a child is presented, and the differential diagnoses with other polyarthritis are offered. Synovial biopsy of both knees at different ages showed the presence of PSV in a fourteen years old boy with a nine years history of painless swelling of wrist, knees and ankles. Painless polyarticular swelling with few inflammatory signs, negative acute-phase laboratory tests, normal synovial fluid, periarticular soft tissue swelling on plain films and a mandatory synovial biopsy are the diagnostic clues of this rare presentation.