Linear Mucosal Defect in Nintedanib-associated Colitis: A Rare Case with Collagenous Colitis-like Features

A 70-year-old man with idiopathic pulmonary fibrosis undergoing nintedanib treatment for 2 years experienced worsening diarrhea, which prompted colonoscopy. An examination revealed a coarse mucosal appearance and erosion extending from the rectum to the ascending colon with linear mucosal defects in the sigmoid colon. Histopathological findings from the biopsies demonstrated features resembling those of collagenous colitis (CC). The diarrheal symptoms resolved rapidly after nintedanib withdrawal. The patient was subsequently diagnosed with nintedanib-associated, drug-induced colitis with CC-like features. Although linear mucosal defects linked to proton pump inhibitors, particularly lansoprazole, have been reported in CC, they have not been previously described in nintedanib-associated colitis.