In this study, we demonstrated that the frequency of thyroid diseases, including GD and HT, is high in HLA-DRB1*04:10-positive MMD patients compared with that in HLA-DRB1*04:10-negative MMD patients, suggesting the relationship between the HLA-DRB1*04:10 haplotype and MMD and autoimmune thyroid diseases. This evidence concerns the gene HLA-DRB1 and multiminicore myopathy.