Considering that most of our patients reported having a White relative, and that the most frequent allele and haplotype were DRB1*03:01 and 03:01~05:01g~02:01, respectively (probably European-Caucasian derived), we can link the ancestry of patients with T1D in Brazil back to European, Caucasian ethnicity. Here, HLA-DRB1 is linked to type 1 diabetes mellitus.