While both Primary Age-Related Tauopathy (PART) and Alzheimer’s Disease (AD) involve the accumulation of hyperphosphorylated tau (pTau)-positive neurofibrillary tangles (NFTs) in the hippocampus, PART is distinguished by the absence of β-amyloid (Aβ) deposition and is generally associated with milder cognitive impairment than AD. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.