While the past genome-wide association study (GWAS) for autoimmune thyroid diseases (AITDs) was done in Caucasians, a recent GWAS in Caucasian patients with both AITD and type 1 diabetes [a variant of autoimmune polyglandular syndrome type 3 (APS3v)] identified five non-HLA genes: BCL2L15, MAGI3, PHTF1, PTPN22, and GPR103. The aim of our study was to replicate these associations with AITD in a Japanese population. This evidence concerns the gene MAGI3 and type 1 diabetes mellitus.