Presenilin 1 (PS1) was found as part of a search for an early-onset FAD gene associated with a locus on chromosome 14.8 Mutations in PS1 are the most commonly recognized causes of early-onset FAD, and to date, more than 160 mutations in PS1 linked to FAD have been discovered (see http://www.molgen.ua.ac.be/ADMutations). Mutations in a related gene on chromosome 1, now called presenilin 2 (PS2), were soon linked to FAD as well.8
