IgA Nephropathy that Developed as an Immune-related Adverse Event of Pembrolizumab Complicated with Interstitial Nephritis.

A 70-year-old man received pembrolizumab as a second-line treatment for squamous cell lung cancer of the lower right lobe. After three courses, proteinuria and hematuria were observed, which worsened after seven courses. He was diagnosed with a combination of IgA nephropathy and active interstitial nephritis. Steroid pulse therapy was started, and the dose of prednisolone was gradually reduced from 60 mg/day. Renal dysfunction as an immune-related adverse event of pembrolizumab monotherapy for non-small cell lung cancer has been reported previously. Therefore, establishing a system for the early detection and treatment that distinguishes immune-related glomerular diseases is essential.