Cobalamin deficiency as a result of pernicious anemia occurs frequently in patients with T1DM—patients with T1DM actively exhibit autoantibodies to intrinsic factor type 1 and 2 and parietal cell antibodies, in particular those with glutamate decarboxylase-65 antibodies and HLA-DQA1*0501-B1*0301 haplotype [172]. The gene discussed is HLA-DQA1; the disease is type 1 diabetes mellitus.