Neuritic plaques in the Lewy body variant of Alzheimer disease lack paired helical filaments

The Lewy body variant of Alzheimer disease (LBV) is a distinct category of dementia which, unlike pure diffuse Lewy body disease (DLBD), meets clinical and neuropathologic criteria for Alzheimer disease (AD) but differs from pure AD in having a neocortical predominance of diffuse and neuritic plaques (NP), with very few neurofibrillary tangles (NFT). We investigated the immunoreactivity of NP with a monoclonal antibody against paired helical filaments (PHF) composed of phosphorylated microtubule associated protein tau. With routine thioflavin-S preparations, 12 LBV and 14 AD cases had similar numbers of NP, but the LBV had significantly (P < 0.05) fewer NFT per microscopic field in the midfrontal cortex. Among subjects with midfrontal NFT, 81-84% of NP in AD and LBV were anti-PHF positive. Among subjects without midfrontal NFT, 52% of NP in AD but only 12% of NP in LBV cases were anti-PHF positive (P < 0.05). LBV differs from AD in that its NP generally do not contain PHF, unless they are accompanied by neocortical NFT. (C) 1997 Elsevier Science Ireland Ltd.