Alzheimer’s disease (AD) is a heterogeneous disorder considering its clinical symptoms, rate of progression, neuropathological profiles and biomarkers.1 The factors accounting for this heterogeneity are multiple, including age-at-onset, apolipoprotein E genotype (APOE) and other risk genes, lifestyle factors and comorbidities. This evidence concerns the gene APOE and early-onset autosomal dominant Alzheimer disease.