Abstract
The presenilins are two closely related genes which implication in familial Alzheimer's disease (FAD) is well known. Presenilin 1 gene (PS1) mutations cause heterogeneous disorders and a bibliographical review of atypical PS1-FAD cases allows us to describe a great diversity of neuropathological and clinical variations and conclude that most of them do not strongly depend on the genetic location of the mutation so other genetic or epigenetic factors may be involved.