Pralsetinib-Induced Lymphocytic Colitis.

Lymphocytic colitis (LC) is a subtype of microscopic colitis, often associated with chronic watery diarrhea and characterized by an increase in intraepithelial lymphocytes. Although various medications are implicated in drug-induced LC, its incidence as a treatment-related adverse effect of rearrangement during transfection-selective tyrosine kinase inhibitors is not known. We report a case of pralsetinib-induced LC in a patient with stage 3c nonsmall cell lung cancer. This case highlights pralsetinib-induced LC as a cause of persistent diarrhea that is refractory to standard antidiarrheal treatments and prompts gastrointestinal evaluation and histopathological examination to facilitate early diagnosis and management.