Notably, we found that the SNP with the highest association with T1D susceptibility and IgG autoantibody reactivity (rs1950942) was also associated with anti-GAD IgM reactivity in T1D patients (P = 5.98E−03) and in non-affected parents (P = 4.17E−03). This evidence concerns the gene CD40LG and type 1 diabetes mellitus.