This cluster of papers focuses on the epidemiology, pathophysiology, diagnosis, and treatment of microscopic colitis, including collagenous colitis and lymphocytic colitis. It covers topics such as budesonide treatment, histological features, drug-induced colitis, and the association with other gastrointestinal tract disorders and inflammatory bowel disease. The papers also discuss the impact of proton pump inhibitors and other medications on the development of microscopic colitis.