Many studies have consistently reported that the hyperphosphorylation of tau at several residues (serine, threonine, or tyrosine) may occur at various stages of disease progression, but the phosphorylation of tau proteins at sites Ser 396–404 is considered, by some authors, to be one of the earliest events in Alzheimer’s disease. Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.