Building upon the understanding of genetic and immune factors in T1D, the detection of autoantibodies against key beta-cell antigens—such as insulin, glutamate decarboxylase (65) (GAD65), zinc transporter 8 (ZnT8), and insulinoma antigen-2 (IA-2)—provides a powerful diagnostic tool (7). Here, GAD2 is linked to type 1 diabetes mellitus.