Renal Immune-Related Adverse Event Difficult to Diagnose during Nivolumab Treatment for Hypopharyngeal Carcinoma: Case Report.

Introduction: Immune-related adverse events (irAEs) from nivolumab can affect any organ, but renal impairment is less common than effects on other organs. We encountered a case in which a renal irAE was difficult to diagnose due to mild renal dysfunction. Case Presentation: We report the case of a 65-year-old man with hypopharyngeal carcinoma treated with radiotherapy and cisplatin. Histopathological examination after reconstructive surgery showed extranodal invasion. Two months after completing treatment, computed tomography showed multiple lung metastases. We determined that the tumors were platinum-resistant and initiated treatment with nivolumab. Pyuria, worsening renal function, and elevation of C-reactive protein (CRP) to 16 mg/dL were observed 203 days after the first dose and nivolumab was discontinued. We considered the possibility of renal irAE but did not perform renal biopsy because creatinine was not highly elevated. We administered antibiotics for urinary tract infection, but CRP rose to 20 mg/dL and his general condition gradually worsened. Arthralgia in both knees and elbows appeared around the same time and gallium scintigraphy showed polyarticular accumulations. After diagnosing irAE arthritis, 20 mg of prednisolone was administered. Arthralgia and inflammatory responses improved, along with urinary findings and tubular markers. Retrospectively, pyuria, mild renal dysfunction, and elevated CRP were considered to reflect renal irAE. Conclusion: In some cases of mild renal dysfunction, as in the present case, biopsy may not be performed and the diagnosis may be missed. Renal irAEs should be kept in mind when abnormal urinalysis results and renal dysfunction are observed.