In AD, this is exemplified by the association between propensity for hypercholesterolemia and AD risk in carriers of the ε4 variant allele of apolipoprotein E (APOE4), of which is present in as many as 65% of sporadic and late-onset familial AD cases, and is the greatest risk factor in non-familial cases (Dass et al., 1985; Saunders et al., 1993; Lin-Lee et al., 2002). The gene discussed is APOE; the disease is familial hypercholesterolemia.