Presence of co-pathology in sporadic early-onset Alzheimer disease versus dominantly inherited Alzheimer disease.

DIAD cases show greater neuritic plaque density and more severe CAA than sEOAD cases, but comparable Braak NFT stages. The similar frequencies of LBD in both cohorts may be linked to severe AD neuropathological change, rather than co-incident age-related pathologies. Future studies should include methodologically uniform assessments of both cohorts to explore age-related and non-age-related mechanisms that may account for differences in the burdens of ADNC lesions and non-AD co-pathologies.