APOE and Alzheimer disease: The same metabolic changes have been noted in cognitively normal subjects homozygous for a susceptibility gene, the apolipoprotein E (APOE) e4 allele,130,135 asymptomatic carriers of genetic mutations associated with early onset familial AD,128,129,136 and those with a maternal family history of AD, as compared to those with a paternal history or no family history of AD.137