APP and early-onset autosomal dominant Alzheimer disease: Variants in the Presenilin-1 (PSEN1) gene, Amyloid Precursor Protein (APP) gene, and Presenilin-2 (PSEN2) gene cause early-onset familial AD (EOFAD), with more than 200 mutations described worldwide (VIB-UAntwerp, 2018; Mendez, 2019; Qin et al., 2020; Xiao et al., 2021).