Epidemiological studies highlighted the ε4 allele of Apoe as the most common risk factor for late-onset Alzheimer's disease [186], and in vitro studies showed a colocalization of apoE with amyloid plaques [187] and a positive correlation between plaque density and number of ε4 alleles in Alzheimer' patients at autopsy [188]. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.