Polyarticular pigmented villonodular synovitis in a child.

Pigmented villonodular synovitis is rare in the younger child. Polyarticular involvement in this condition, regardless of patient age, is distinctly uncommon. The authors describe a case of pigmented villonodular synovitis involving multiple joints in a young boy who also had congenital anomalies of the genitourinary tract. Although rare, pigmented villonodular synovitis should be considered in the differential diagnosis of multiple joint swellings in children with congenital anomalies.