GAD1 and nervous system disorder: Disease-specific anti-GAD Ab epitopes in type 1 DM and neurological disorders, such as Stiff Person Syndrome (SPS), were evident already in the early 90s, when Baekkeskov et al. found that anti-GAD Abs in patients with SPS recognized both linear and conformational GAD epitopes, while those in patients with type 1 DM were dependent on the conformation integrity of the molecule [36].