Patients with a double dose of HLA-DQB1*02 exhibited more often classical phenotype and villous atrophy, as compared to those with a single dose of the allele, whereas no evidence of gene dose effect was collected on diarrhea, age at diagnosis, the severity of villous atrophy, and the frequency of type 1 diabetes mellitus (Table 2). This evidence concerns the gene HLA-DQB1 and diabetes mellitus.