APOE and Alzheimer disease: APOE is the greatest genetic risk factor for sporadic AD and the ε4 allele confers the greatest risk (Corder et al., 1993; Strittmatter et al., 1993) although many additional susceptibility genes, particularly related to amyloid, tau, immunity, lipids and endocytosis, have been identified by Genome-wide association studies (GWAS) (Bellenguez et al., 2022).