Rapid exacerbation of bilateral hip osteoarthritis induced by immune checkpoint inhibitor therapy: A case report

Immune checkpoint inhibitors (ICIs) have revolutionised cancer therapy but are associated with immune-related adverse events, including musculoskeletal symptoms. We report a case of rapid exacerbation of bilateral hip osteoarthritis (OA) induced by nivolumab. A 56-year-old woman with a history of developmental hip dysplasia and malignant melanoma was treated with nivolumab. Following nivolumab administration, she developed severe bilateral hip pain and polyarthralgia, necessitating drug discontinuation. Despite cessation of the ICI, her symptoms persisted, accompanied by elevated C-reactive protein levels. Imaging showed end-stage OA with joint space narrowing and increased 18F-fluorodeoxyglucose uptake in both hip joints. She underwent staged bilateral total hip arthroplasty. Intraoperative pathology showed marked synovial hyperplasia. Immunohistochemical analysis showed diffuse positivity for CD68, tumour necrosis factor-α, interleukin-6, programmed cell death protein 1, and programmed death-ligand 1, findings consistent with an immune-mediated inflammatory process superimposed on degenerative changes. Postoperatively, her hip pain and associated symptoms gradually improved, accompanied by normalisation of inflammatory markers during follow-up. Histological evidence suggests that programmed cell death protein 1/programmed death-ligand 1 blockade may locally amplify inflammation within the osteoarthritic joint. Clinicians must be vigilant regarding the potential for ICIs to rapidly worsen underlying joint disease, warranting timely surgical intervention when conservative management fails.