A systematic search was conducted in PubMed (January 2018 to December 2024) using the combined keywords: (“calprotectin” OR “S100A8/A9”) AND (“IBD” OR “inflammatory bowel disease” OR “Crohn’s disease” OR “ulcerative colitis” OR “gastrointestinal disorders”) AND (“therapy” OR “treatment” OR “diagnosis” OR “management”). The gene discussed is S100A8; the disease is ulcerative colitis.