PSEN1 and Alzheimer disease: The latter (vCJD 27) was identified on exome sequencing to have the PSEN1 p.E318G variant that increases the risk of AD in APOE-ɛ4 carriers (but possibly not relevant in the APOE ɛ2/3 genotype) [2], and the −48 C/T polymorphism in the PSEN1 promoter that is associated with an increased risk of AD and an increased Aβ load in the brain [37], which might be of relevance to the finding of sparse diffuse Aβ brain parenchymal deposits at 30 years of age.