The amyloid accumulation pathway includes PSEN1, encoding a subunit of γ-secretase, which is the most common gene associated with EOAD and has the greatest number of pathogenic mutations, followed by amyloid precursor protein (APP) and PSEN2; mutations in these AD genes are associated with the build-up of Aß peptides in the brain. Here, PSEN1 is linked to Alzheimer disease.