Mutations in APP, PSEN1/PSEN2 -which code for the catalytic subunit of the γ-secretase complex- and BRI2/ITM2B -which codes for an inhibitor of APP processing by BACE1- cause familial forms of AD and the AD-like Familial Danish Dementia [1], [7]–[12]. The gene discussed is PSEN2; the disease is Alzheimer disease.