APOE and Alzheimer disease: Various other observations support PART as a separate pathological entity: the absence of an association between PART and APOE ε4 allele, the strongest risk factor for AD [3, 15]; “ghost” tangles, i.e. extracellular tangles, are more frequently found in PART than AD patients [17]; and patients diagnosed with PART are frequently in the 8th–9th decades, as was found in our study, making it highly improbable that Aβ deposition would only start then [20].