A number of studies have pointed out abnormalities in the vesicular-mediated pathway in early and sporadic Alzheimer’s disease.34–36,38,39 Studies of human donor tissue by Cataldo et al.34,35 have revealed that at the earliest stages of Alzheimer’s disease, many neurons have increased levels of Aβ and exhibit an abnormal overactivation of Rab5-positive early endosomes. This evidence concerns the gene RAB5A and early-onset autosomal dominant Alzheimer disease.