The concentration of homocysteine (Hcy), glutathione (GSH), 8-oxo-2’-deoxyguanosine (8-oxo2dG) and 8-oxoguanine DNA glycosylase (OGG1) in plasma of Alzheimer’s disease (AD) patients and related (RC) and unrelated controls (UC), stratified according to APOC1’638 genotype. This evidence concerns the gene OGG1 and early-onset autosomal dominant Alzheimer disease.