Localised intraarticular pigmented villonodular synovitis in an adolescent patient: a case-based review of the literature

Abstract Introduction Pigmented villonodular synovitis (PVNS) is a rare, locally aggressive subtype of tenosynovial giant cell tumours that affect the synovium of the joints and tendons, occurring either focally or diffusely associated with the deposition of hemosiderin into the involved joint(s) and soft tissues. Although PVNS is historically considered an inflammatory process, recent evidence suggests the possibility of a neoplastic transformation. In addition, despite being typically found as a monoarticular knee disorder, other large and small joints can also be affected. The disease is rarely reported in African children, with most reported cases not histologically confirmed. We, therefore, present the first histologically proven case of localised intraarticular PVNS in an African teenager who presented with unilateral left knee swelling and pain. Method/Setting We report the case of a 16-year-old male teenager who presented to the rheumatology clinic with a nine-month history of non-traumatic anterior left knee swelling and pain that increased over time with associated difficulty walking and standing without aid. After clinical examination and relevant investigations, Magnetic Resonant Imaging (MRI) was done to confirm our suspicion of PVNS. Findings/Treatment Examination revealed a tender, swollen knee with a fluctuant palpable infrapatellar mass. Knee arthrocentesis yielded about 200mls of non-clotted hemorrhagic effusions. The patient had an open synovectomy following MRI, which was highly suggestive of pigmented villonodular synovitis with extensive suprapatellar bursitis. Specific histological findings (below) further confirmed the diagnosis. He commenced early physiotherapy, and symptoms resolved without recurrence of swelling eleven months after surgery. Conclusion This case highlights the visual presentation of an uncommon joint disorder and suggests it is considered a differential diagnosis of non-traumatic monoarticular pain and swelling in our rheumatology clinic set-up and among teenagers in whom juvenile rheumatoid arthritis would have been the first differential. Key words: Pigmented villonodular synovitis, Synovectomy, Multinucleated giant cells Contribution statement: AA conceived the idea to write the case report, draft the first manuscript, and manage the patient. YA, HO and AF edited the manuscript, while AIL interpreted the histological findings. All the authors approved the final version of the manuscript. Disclosure statement: None declared. Ethics and patient consent: This case report adheres to the Helsinki declaration, and the patient’s parents gave written consent to publish the details of the information. Additional information: Any institution did not fund this publication. Acknowledgements: We thank Dr Isaac Akanbi and Dr Bukar for interpreting the MRI and performing the surgery.