Patients with certain genetic factors, including HLA, autoimmune regulator (AIRE) gene, protein tyrosine phosphatase non-receptor type 22 (PTPN22), forkhead box P3 (FOXP3) protein, interleukin-2 receptor (IL2RA), and Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), are more susceptible to developing both AITD and T1D [30]. Here, CTLA4 is linked to type 1 diabetes mellitus.