In relation to neurons, autopsies of brains from patients with AD have shown increased BACE1 expression, which is associated with neuronal degeneration and elevated Aβ levels in the cerebral cortex compared to age-matched controls.32 Therefore, the presence of endothelial BACE1 expression in patients with CAA31 and neuronal BACE1 expression in patients with Alzheimer’s disease (AD)32 underscores the necessity of maintaining a balance between endothelial and neuronal functions in both amyloidogenic and non-amyloidogenic pathways. This evidence concerns the gene BACE1 and Alzheimer disease.