MAPT and early-onset autosomal dominant Alzheimer disease: From a neuropathologic standpoint, AD is defined by the simultaneous presence of Aβ plaques and tau aggregates, satisfying the criteria for Alzheimer's disease neuropathologic change (ADNC).[6] However, this dual pathology hinders the investigation of tau hyperphosphorylation as an independent process, thereby limiting the identification of common mechanisms across different tauopathies.