Immune‐Checkpoint‐Inhibitor‐Related Bullous Pemphigoid During Avelumab Maintenance Therapy in a Patient With Metastatic Renal Pelvic Carcinoma: A Case Report - Taketoshi Nara; Kengo Furihata; Akane Kikuchi; Yuya Sekine; Hiromi Sato; Mizuki Kobayashi; Ryohei Yamamoto; Mitsuru Saito; Shintaro Narita; Tomonori Habuchi (IJU Case Reports, 2026)