PSEN1 and Alzheimer disease: Mutations in APP, PS1, and PS2 genes, favor the production of the Aβ42 peptides and this, together with the presence of the amyloid plaques, shaped the “Amyloid Hypothesis” that proposes the imbalance between production and clearance of Aβ42 as the main cause of AD development (Selkoe and Hardy, 2016).