MAPT and Alzheimer disease: We report that (i) over 50% of iCJD cases harbored significant Aβ pathology, which included cerebral amyloid angiopathy (CAA) in all cases; (ii) the prevalence of the Aβ-positive iCJD subset was significantly higher than that of Aβ-positive sCJD cases, which were on average 17 years older; (iii) p-tau pathology was present but did not distinguish Aβ-positive iCJD cases from the sCJD controls, and seemed to be age-related; (iv) the phenotypic characteristics of the Aβ pathology in iCJD were distinct from those of typical AD.