APOE and Alzheimer disease: Also, an imaging based study showed that the APOE E4 allele underlies higher brain vulnerability not only in AD but also in FTD and that other concomitant genetic and/or environmental factor(s) might modulate the detrimental effects of APOE E4 leading to the different regional vulnerability that is at the basis of the topographical differences in the affected areas in AD (mediotemporal) and FTD (frontotemporal) (Boccardi et al., 2004).