The similarity between tau pathology in PART-NC and ADNC, along with the difficulty in defining when PART (if amyloid pathology is also present) should be classified as AD rather than PART + AD, raises questions about whether PART should be considered a distinct clinicopathological entity (Irwin et al. 2016; Duyckaerts et al. 2015). This evidence concerns the gene MAPT and Alzheimer disease.