PSEN1 and Alzheimer disease: Mutations in genes such as amyloid precursor protein (APP),presenilin 1 (PSEN1), and presenilin 2 (PSEN2) are associated withearly-onset FAD, leading to increased production or altered processingof β-amyloid.45 The apolipoproteinE (APOE) ε4 allele is the strongest genetic risk factor forlate-onset Alzheimer’s disease (LOAD) and is associated withincreased β-amyloid deposition and enhanced risk of developingAD.