While GAD antibodies in autoimmune endocrinopathies recognize conformational epitopes on GAD65 and the infrequent recognition of GAD67 isoform is assumed as cross-reactivity phenomenon [9], the antibodies in SPS and cerebellar ataxia recognize linear epitopes on GAD65 so they can be detected by Western blotting and frequently recognize GAD67 [10, 11, 12, 13]. The gene discussed is GAD1; the disease is stiff-person syndrome.