PTPN2 and type 1 diabetes mellitus: Notably, it was found that mutations in autoimmune-related genes overlap between IBD and type 1 diabetes (T1D), such as protein tyrosine phosphatase non-receptor type 2 (PTPN2) and PTPN22, which negatively regulate T-cell activation (111) and alter the composition of the gut microbiota in IBD patients (112).