Autoantibodies directed against islet autoantigens such as insulin, glutamic acid decarboxylase 65 (GAD 65), islet antigen-2 (IA-2) and Zinc transporter 8 (ZnT8) have been demonstrated to be markers of the islet autoimmunity that precede clinical onset of T1D [9,10] (Fig. 1). Here, GAD2 is linked to type 1 diabetes mellitus.