PSEN2 and Alzheimer disease: Familial AD is caused mainly by mutations in the amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) genes (Hoogmartens et al., 2021), which lead to Aβ1-42/Aβ1-40 overexpression and deposition in brain tissue.