Since the chronic immune conditions to which PTPN2 is linked - Crohn’s disease (CD), ulcerative colitis (UC), celiac disease, type 1 diabetes, and rheumatoid arthritis – all share a dysfunctional intestinal barrier early in disease, multiple studies addressed the impact of PTPN2 alleles on epithelial barrier function. The gene discussed is PTPN2; the disease is type 1 diabetes mellitus.