GAD1 and type 1 diabetes mellitus: Autoantibodies against Glutamic Acid Decarboxylase (GAD), the rate-limiting enzyme for the synthesis of the inhibitory gamma-aminobutyric acid (GABA), originally seen in patients with Stiff Person Syndrome (SPS), epilepsy and Type-1 Diabetes Mellitus (DM-1) [1, 2], are now connected with several neurological autoimmunities characterized by neuronal excitability comprising the “GAD antibody-spectrum disorders (GAD-SD)” [3–8].