Differences in DNA methylation have been reported both in blood and brain tissue [44, 45] of Alzheimer’s disease cases compared to healthy controls, especially in gene regions associated with AD pathology, including apolipoprotein E (ApoE) and the amyloid precursor protein (APP) but also in other genes [61–68]. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.