PTPN22 and type 1 diabetes mellitus: Additional loci initially associated to T1D prior to application of GWAS include protein tyrosine phosphatase, non-receptor type 22 (PTPN22) gene [37, 38], interleukin 2 receptor alpha (IL2RA) [39, 40], ubiquitin-associated and SH3 domain-containing protein A (UBASH3A) [41] and interferon-induced helicase c domain-containing protein 1 (IFIH1) [33, 42].