In particular, mutations in the genes encoding for presenilin 1 (PSEN1), presenilin 2 (PSEN2) and amyloid precursor protein (APP) are associated with early-onset forms of AD, while ε4 and ε2 variants of the apolipoprotein E APOE gene can influence AD susceptibility [5]. The gene discussed is APOE; the disease is Alzheimer disease.