The apolipoprotein E gene (APOE) has three major variants, APOE2, APOE3 and APOE4; so far APOE has been confirmed as the strongest genetic risk modifier for late-onset Alzheimer’s disease (AD), with the APOE4 conferring an increased risk and the APOE2 conferring a decreased risk relative to the common APOE3 allele [1,2]. Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.