GAD2 and stiff-person syndrome: Importantly, SPS shares autoimmune associations with other conditions, particularly type 1 diabetes mellitus (T1DM): GAD65 autoantibodies are detected in 80 % of newly diagnosed T1DM patients (Patel et al., 2020, Balint and Bhatia, 2016), though antibody titers in SPS are significantly higher (Bai et al., 2022, Trier et al., 2022).