Degenerative terminals of the perforant pathway are human alpha-synuclein-immunoreactive in the hippocampus of patients with diffuse Lewy body disease.

We investigated the hippocampal pathology in diffuse Lewy body disease (DLBD) using alpha-synuclein immunohistochemistry. Ubiquitin-positive intrahippocampal structures caused by the degeneration of terminal axons of the perforant pathway were observed to be alpha-synuclein immunoreactive. These alpha-synuclein-positive degenerative terminals contained granulo-filamentous or vesiculo-tubular components similar to those of Lewy bodies (LB) immunoelectron microscopically, suggesting that alpha-synuclein may abnormally aggregate into filamentous or membranous cytoskeletal components including neurofilaments and synaptic vesicles in DLBD. A 'dying back' degenerating process due to a blockage of axonal transport may explain why the degenerative terminals and LB share similar alpha-synuclein-positive components, but the origin cells of the perforant pathway contain only a few LB.