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Neurofibrillary pathology in Alzheimer disease with Lewy bodies: two subgroups
1Veterans Affairs Medical Center and the Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA.
Background:
While NFT frequency is reportedly reduced in AD+DLB, we often encounter abundant neocortical NFTs in such cases and decided to investigate this discrepancy.
Objective:
To compare neurofibrillary tangle (NFT) frequency in Alzheimer disease with concomitant dementia with Lewy bodies (AD+DLB) with NFT frequency in "pure" AD.
Methods:
Neurofibrillary tangle frequency, as well as regional staging of neurofibrillary degeneration modified from Braak, was scored in 160 autopsy cases of primary dementia (80 AD+DLB cases and 80 pure AD cases).
Results:
Neurofibrillary tangle and modified Braak scores were lower in AD+DLB, as reported previously. Yet, neocortical NFT scores assumed markedly different patterns in the 2 groups (P = .001). In pure AD, NFT scores of "frequent" were predominant: more cases exhibited frequent than moderate or sparse NFTs. In AD+DLB, the distribution of NFT scores was bimodal: NFTs were either frequent or few to absent. Neocortical NFT scores in the AD+DLB group tended to parallel the severity of other types of tau cytopathology (neuropil threads and tau-positive plaque neurites).
Conclusions:
Cases of AD+DLB may be divided into 2 subgroups based on the extent of neocortical neurofibrillary pathology. These findings could have implications for disease pathogenesis and treatment.