DQA1/DQB1 Heterodimers 0501/0201 and 0501/0302 were more frequent in both APS-2 cohorts compared to controls: 0501/0201: AD/AIT OR 3.2; p = 0.02; T1D/AIT OR 4.0; p = 0.004; 0501/0302 AD/AIT and T1D/AIT OR 8.5; p = 0.03. This evidence concerns the gene HLA-DQA1 and Alzheimer disease.