PSEN1 and behavioral variant of frontotemporal dementia: For example, as shown here and elsewhere,18 mutations in PSEN1 and PSEN2 can present with a behavioral FTD syndrome, in which the clinical syndromes of bvFTD and behavioral variant AD4 become almost clinically indistinguishable (for more extensive discussions of these two mutation carriers see Blauwendraat et al.19).