This finding is compatible with a causal link between plasma p-tau metabolism and brain amyloid-β accumulation as previously suggested.5 Although the mechanisms underlying this putative causality need further study, our data underscore the usefulness of plasma p-tau as a very early diagnostic and prognostic biomarker of Alzheimer’s disease pathology. The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.