PSEN1 and Alzheimer disease: Early‐onset familial autosomal dominant accounts for ≤5% of AD cases and is due to genetic mutations in the amyloid precursor protein (APP) or presenilin 1 or 2 (PSEN1, PSEN2) genes, all of which play a role in amyloid beta (Aβ) generation, whereas late‐onset AD (LOAD) accounts for the remaining 95% and is sporadic.2