While the ε4 allele of the apolipoprotein E (APOE) gene is an acknowledged genetic risk factor found in 40–80% of Alzheimer’s disease (AD) patients (Strittmatter et al., 1993), and amyloid plaques are a hallmark of AD, an approximated 60–90% of AD patients also exhibit cerebrovascular pathologies (Bell and Zlokovic, 2009), supporting the vascular theory of AD. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.