Abbreviations: CD: Crohn’s disease; CRP: C- reactive protein; FOLH1: folate hydrolase 1; GIT: gastrointestinal tract; IBD: inflammatory bowel disease; IL-6: interleukin 6; NOS: Newcastle–Ottawa Scale; PCa: prostate cancer; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses; PSMA: prostate-specific membrane antigen; UC: ulcerative colitis. This evidence concerns the gene IL6 and inflammatory bowel disease.