Seronegative Rheumatoid Arthritis Secondary to Immune Checkpoint Inhibitor in a Renal Cell Carcinoma Patient Encountered in a Rural Community-Based Rheumatology Clinic: A Case Report.

Immune checkpoint inhibitors (ICIs) are a widely used class of cancer immunotherapy. Those drugs have improved the treatment of cancer since its introduction in the 2000s. Nivolumab is an ICI that can be used for previously untreated renal cell carcinoma. Immune-related adverse events (irAEs) are a type of adverse event of immunotherapy that is associated with an overreactive immune system. We report a case of a 69-year-old Caucasian man with stage IV renal cell carcinoma who presented to a rural community-based rheumatology clinic referred by his oncologist, after starting to develop morning stiffness for at least three hours, joint swelling, warmth, and erythema five months after starting immunotherapy with nivolumab. The patient was diagnosed with seronegative rheumatoid arthritis secondary to ICIs and required a higher dose of prednisone (up to 40 mg per day) with methotrexate to achieve remission. With the widespread availability of ICIs, rheumatologic irAEs can be encountered in a rural community-based practice. Practicing physicians taking care of cancer patients need to be aware of the adverse effect of ICIs.