Previous studies have shown the dose dependent role of apolipoprotein E (ApoE) ε4 allele as a risk factor for developing Alzheimer's disease, increasing the risk of AD by 2.6 to 14.9 fold and lowering the onset by 7 to 15 years (Farrer et al., 1997; Thambisetty et al., 2010a). Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.