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Pigmented villonodular synovitis and rheumatoid arthritis: diagnostic challenges and therapeutic considerations in a case of knee pain
  1. Nur Barlas1,
  2. Sait Barlas1,
  3. Emre Adalier2 and
  4. Shristi Basnyat3
  1. 1Department of Internal Medicine, Florida State University-Cape Coral Hospital, Cape Coral, Florida, USA
  2. 2Harvey School of Medicine, University of Pavia, Pavia, Lombardia, Italy
  3. 3Department of Rheumatology, Florida State University- Lee Health, Bonita Springs, Florida, USA
  1. Correspondence to Dr Nur Barlas; nur.barlas{at}


We present a case of a woman in her 30s who visited the rheumatology clinic due to her persistent knee pain for 5 years, which spread to multiple joints. She was diagnosed with seropositive rheumatoid arthritis (RA). While most joints responded well to methotrexate and subsequently etanercept, persistent unilateral knee pain prompted further investigation. Imaging revealed synovitis and joint effusion in her knee, prompting arthroscopy and synovial biopsy, revealing pigmented villonodular synovitis (PVNS). Despite initial success with a tricompartmental synovectomy, her disease recurred. The decision was made to pursue medical therapy, with pexidartinib initiated by the oncology team. Our case report highlights the importance of considering other underlying conditions in patients with RA who do not achieve full clinical improvement despite standard treatment. Physicians should remain vigilant for atypical presentations and imaging features in patients with RA, for early recognition of PVNS can significantly impact treatment decisions and patient outcomes.

  • Rheumatoid arthritis
  • Oncology
  • Malignant and Benign haematology

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  • Contributors All the authors have contributed to the conception, design, analysis, interpretation and drafting of this case report. All authors have approved the final version of the manuscript and agree to be accountable for all aspects of the work, ensuring that questions related to the accuracy and integrity of any part of the work are appropriately investigated and resolved. The specific contributions of each author are as follows. NB: conceived and designed the study, collected and interpreted the patient data and drafted the initial manuscript. SB: assisted in data collection, conducted a literature review, contributed to the interpretation of findings and critically revised the manuscript for intellectual content. EA: contributed to the literature review and analysis of related cases. ShB: supervised the overall study, provided guidance throughout the research process and reviewed and edited the manuscript for important intellectual content. Chatgpt V.3.5 was used to aid with grammatical correction.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.