PSEN2 and Alzheimer disease: Early-onset Alzheimer’s disease is an autosomal dominantly inherited form of Alzheimer’s disease (AD) that represents a prevalence of 5.3/100,000 persons at risk (41–60 years) [8] and is caused by mutations in three different genes: presenilin-1 (PSEN1), presenilin-2 (PSEN2) and amyloid protein precursor (APP), with most of the mutations in PSEN1 [8].