Pigmented villonodular synovitis: Four pediatric cases and brief review of literature

Pigmented villonodular synovitis (PVNS) is a rare benign disorder of a joint which affects its synovium, tendon sheaths and bursas. While most cases of PVNS are adult patients aged between 20-50 years, few afflicted children have also been reported. Clinical signs of PVNS are insidious and non-specific. Pain, swelling and stiffness are the major symptoms. Magnetic Resonance Imaging (MRI) is the best radiological method for diagnosis of PVNS, as the initial X-ray is normal in early phase of disease in most cases. Therefore, diagnosis is often delayed or confused with mechanical disorders, haemophilic arthropathy, tuberculosis, juvenile idiopathic arthritis (JIA), and other disorders. Four paediatric PVNS cases are being reported in this case series with the aim to highlight that PVNS should be considered in the differential diagnoses of chronic monoarthritis. Two of our cases were initially misdiagnosed as JIA and the remaining two as Familial Mediterranean fever (FMF). They did not respond to conventional anti-inflammatory treatment and eventually only benefited from surgery. These four cases emphasize that the radiologist and clinician should collaborate carefully while managing any child with monoarthritis to ensure that the diagnosis of PVNS is not missed.