It is well known that PSEN1 mutations give rise to Alzheimer’s disease by affecting the beta amyloid levels; however, a few mutations have been reported as associated with a FTD phenotype, even pathologically confirmed as a tauopathy (Dermaut et al., 2004), although how loss of functional presenilin 1 could predispose to tauopathy has not been clarified. This evidence concerns the gene PSEN1 and early-onset autosomal dominant Alzheimer disease.