PSEN1 and Alzheimer disease: PSEN1 p.L166 codon seems to be a very vulnerable site for mutations: 4 different causal mutations (p.L166del, p.L166H, p.L166P, and p.L166R) have been previously described in this same residue in 3 familial AD cases (p.L166R, p.L166P, and p.L166del) (Ezquerra et al., 2000; Knight et al., 2007; Moehlmann et al., 2002) and in 1 pseudo-sporadic case (p.L166H) (Pantieri et al., 2005).