PSEN1 and familial Alzheimer disease: Familial early-onset AD (FAD) is associated with mutated genes such as APP, PSEN1, PSEN2, and MAPT, which also significantly increase the risk for late-onset AD (LOAD) (Ryan and Rossor, 2010), while apolipoprotein E variant ε4 (APOEε4) (Kim et al., 2009) and triggering receptor expressed on myeloid cells 2 (TREM2) are associated with the highest risk of developing LOAD (Wolfe et al., 2018).