PTPN22 and type 1 diabetes mellitus: Variants in PTPN22, HLA-DRB1, INS, IFIH1, CTLA4 and C12orf30 have previously been associated with T1D [21, 23, 24, 33] and variants in most of the above genes have been associated to AITD [4, 14, 34, 39–42] and several other disorders [43–48].