The presence of multiple islet autoantibodies and alleles at the HLA DR and DQ class II loci such as GAD65, IA-2, ZnT8, insulin and cytoplasmic islet cell antibodies (ICA), are considered predictive for the development of clinical T1D among relatives of T1D patients [24]–[30]. Here, GAD2 is linked to type 1 diabetes mellitus.