Recently, it has been reported that increased plasma phosphorylated tau concentration correlates with NFT density and precedes β-amyloid accumulation,9-11 and measurement of plasma phosphorylated tau concentration is expected to be a diagnostic marker for early Alzheimer’s disease.12 Notably, however, these measurements do not necessarily reflect the extent of NFT in the EC. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.