{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,6,6]],"date-time":"2025-06-06T04:25:59Z","timestamp":1749183959576,"version":"3.41.0"},"reference-count":0,"publisher":"MJH Life Sciences","issue":"3904","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2025,5,6]]},"abstract":"<jats:p>Immune checkpoint inhibitors (ICIs) are increasingly used in the treatment of advanced malignancies, but they can cause a wide range of adverse effects, including inflammatory arthritis. Severe ICI-induced inflammatory arthritis (ICI-IA) is rare, and its distinguishing clinical features are not defined. We present a patient with metastatic urothelial carcinoma who developed severe, polyarticular inflammatory arthritis while being treated with an ICI. Arthrocentesis of native and prosthetic joints revealed a significantly elevated white blood cell (WBC) count with a neutrophil predominance. Antibiotics were discontinued when the extensive infectious workup remained negative, and the patient was diagnosed with ICI-IA. This presentation of ICI-IA had overlapping features with septic arthritis, resulting in high diagnostic uncertainty. We comprehensively reviewed all published literature on the clinical features of severe ICI-IA. In the literature, synovial fluid findings revealed variable WBC counts but consistently have a neutrophil predominance. Although severe cases are rare, 9 previously reported cases shared similarities, including polyarticular presentation, elevated inflammatory markers, and absence of other rheumatic disease. Severe ICI-IA appears to have significant clinical overlap with culture-negative septic arthritis. This case report and literature review emphasize that ICI-IA should not be ruled out based on the presence of synovial fluid with elevated WBC with a neutrophil predominance. Early steroid use should be considered.\n\nKeywords: checkpoint inhibitor, inflammatory arthritis, immune-related adverse effects<\/jats:p>","DOI":"10.46883\/2025.25921041","type":"journal-article","created":{"date-parts":[[2025,5,22]],"date-time":"2025-05-22T20:36:32Z","timestamp":1747946192000},"page":"148-152","source":"Crossref","is-referenced-by-count":1,"title":["Synovial Fluid in Checkpoint Inhibitor\u2013Induced Inflammatory Arthritis"],"prefix":"10.46883","member":"25947","published-online":{"date-parts":[[2025,5,16]]},"container-title":["ONCOLOGY"],"original-title":[],"language":"en","deposited":{"date-parts":[[2025,5,22]],"date-time":"2025-05-22T20:36:32Z","timestamp":1747946192000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.cancernetwork.com\/view\/synovial-fluid-in-checkpoint-inhibitor-induced-inflammatory-arthritis"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,5,6]]},"references-count":0,"issue-title":["May 2025"],"journal-issue":{"issue":"3904","published-online":{"date-parts":[[2025,5,13]]},"published-print":{"date-parts":[[2025,5,6]]}},"URL":"https:\/\/doi.org\/10.46883\/2025.25921041","relation":{},"ISSN":["0890-9091"],"issn-type":[{"value":"0890-9091","type":"print"}],"subject":[],"published":{"date-parts":[[2025,5,6]]}}}