Diffuse pigmented villonodular synovitis in a child – what is the best management?

Abstract

Case A 5 year old boy presented to orthopaedics in 2004 with a 3-4 month history of intermittent left knee pain. As examination was normal he required no specific treatment. In 2007, he attended A&E with a spontaneous left knee effusion with a CRP of 9 mg/l, ESR 9 mm/h, raised platelet count of 559 (10/l) and mild neutrophilia of 9.23 (10/l). Knee x-ray was normal. 20 mls of haemorrhagic fluid was aspirated (cultures negative). 2 months later, he was seen by rheumatologists due to fluctuant swelling, initially responding to oral non-steroidals but later requiring an intra-articular injection (20 mg triamcinolone). MRI imaging suggested PVNS. Synovial biopsy or synovectomy was avoided due to risk of post-op stiffness. JIA was considered after 2 left knee flares following upper respiratory tract infections and transient right knee swelling. However, imaging (2007, 2009, 2012) and aspirate appearances were typical of PVNS. Screening over 5 years revealed no evidence of uveitis. He was ANA negative and there was no history of psoriasis. In 2009, a further intra-articular injection (20 mg triamcinolone) was required. The patient remained well and active with ibuprofen and physiotherapy until a preholiday flare in May 2012. His GP injected the knee, after aspirating blood, with 40 mg triamcinolone with no response. He was referred to our service for review. Repeat MRI (Figure 1) showed progressive changes. As the differential diagnosis includes recurrent haemarthrosis, synovial biopsy has been advised.