A severe systemic presentation of pigmented villonodular synovitis in a child with underlying Chediak-Higashi syndrome.

Pigmented villonodular synovitis (PVNS), a condition of synovial hyperproliferation that mostly affects large joints, is rare in children and conventionally lacks systemic symptoms. This report describes a complex paediatric patient who underwent bone marrow transplantation to control the accelerated phase of the Chediak-Higashi syndrome. Diffuse PVNS developed in one knee 2.75 years later. Progression of PVNS was accompanied by the development of severe systemic symptoms, which resolved rapidly following subtotal surgical debridement. The patient remains well with minimal elevation of inflammatory marker levels 10.5 years later. As PVNS and Chediak-Higashi syndrome are both very rare diseases we propose a potential unifying hypothesis for this combination.