PSEN1 and familial Alzheimer disease: AD can be classified into familial Alzheimer’s disease (FAD) and sporadic Alzheimer’s disease (SAD) based on genetic characteristics where FAD is primarily driven by mutations in genes such as APP, PSEN1, and PSEN2, while the pathogenesis of SAD involves complex interactions between genetic and environmental factors, with a significant influence from the pleiotropic effects of the APOE ε4 allele (Blennow et al., 2006; Scheltens et al., 2021).