Therefore, in this study we investigated APOE ε2, ε3 and ε4 alleles, APP-Aβ metabolism genes and the most replicated AD GWAS loci through a genetic screening in 96 early-onset independent familial and apparently sporadic SVID Caucasian patients and 368 elderly neuropathological proven controls (HEX database) and through a differential gene expression study during acute and subacute brain ischemia in a mouse model of vascular dementia and subcortical ischemic stroke. The gene discussed is APP; the disease is Alzheimer disease.