Although the exact pathogenesis of SPS is still unclear, autoantibodies against glutamic acid decarboxylase (GAD), the enzyme responsible for the synthesis of γ-aminobutyric acid (GABA), are found in approximately 60% to 80% of SPS patients, thus suggesting important role of immune system in the etiology of SPS [4,5]. This evidence concerns the gene GAD1 and stiff-person syndrome.