Apolipoprotein E (APOE) is a well‐studied gene that plays a central role in dementia and Alzheimer's Disease (AD) risk, cognition, and other aging‐related traits.[1] The gene encodes the APOE protein that is involved in lipid metabolism, aggregation and clearance of amyloid Aβ, and neuroinflammation.[2] The gene has three prevalent alleles –e2, e3, and e4—that are determined by genotype combinations of the single nucleotide polymorphisms (SNPs) rs7412 and rs429358. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.