Mutations on the genes encoding for APP (Goate et al., 1991), Presenilin-1 (PS1) (Sherrington et al., 1995) and Presenilin-2 (PS2) (Levy-Lahad et al., 1995; Rogaev et al., 1995) are the cause of most familial cases of AD, with the onset of symptoms occurring between 30 and 60 years of age. Here, APP is linked to Alzheimer disease.