Beyond the traditional clinicopathological features, AD may be further categorized by the ATX(N) system, which includes AD biomarkers that are readily detectable in living individuals: (1) Plaques composed of Aβ/amyloid (A), (2) neurofibrillary tangles composed of phosphorylated tau (T), (3) novel biomarkers including immune dysregulation and synaptic dysfunction (X), and (4) neurodegeneration (N) (2–4). Here, MAPT is linked to Alzheimer disease.