PSEN2 and Alzheimer disease: PET imaging has demonstrated amyloid deposition in both cognitively intact and impaired carriers of mutations in PSEN1, PSEN2, and APP, who typically have early onset of AD (Klunk et al., 2007; Remes et al., 2008; Fleisher et al., 2012; Shi et al., 2015; Rodriguez-Vieitez et al., 2016).