The autoimmune nature of SPS was re-confirmed in our series by the: a) presence of high-titer antibodies against GAD in serum and CSF; b) glycine receptor antibodies present in a patient subset; c) frequent association with other autoimmune diseases and autoantibodies, including thyroiditis and Type-1 diabetes; and d) a strong immunogenetic association with DRB1*0301 and DQB1*0201 haplotypes. Here, GAD1 is linked to stiff-person syndrome.