MAPT and tauopathy: The most common and important differential diagnosis would be other 3R + 4R tauopathies, such as primary age-related tauopathy (PART), including senile dementia of the neurofibrillary tangle type (SD–NFT) without amyloid plaques; however, the clinical findings lacked the distinctive features of PART, namely, an obvious memory decline, a late onset (i.e., late-80s), and the characteristic limitation of tau lesions to the medial temporal lobe (37).