Suspected ICI-associated Ureteritis and Cystitis with Biopsy-Proven Acute Interstitial Nephritis

Immune checkpoint inhibitors (ICIs) have transformed cancer treatment but can cause immune-related adverse events (irAEs) in almost any organ [1]. Kidney injury most often presents as acute interstitial nephritis (AIN), whereas ICI-associated ureteritis and cystitis (ICI-UC) are rare and may be mistaken for infection or obstruction [2-5]. Because renal biopsy has rarely been reported in ICI-UC, the contribution of intrinsic kidney injury remains uncertain. We report 2 patients with clinically suspected PD-1 inhibitor-associated ureteritis and cystitis accompanied by biopsy-proven AIN, highlighting intrinsic renal injury in addition to possible obstruction.