Lewy bodies in the amygdala -: Increase of α-synuclein aggregates in neurodegenerative diseases with tau-based inclusions

Background: Increased attention has been given to alpha-synuclein aggregation in nonsynucleinopathies because a-synuclein-containing Lewy bodies (LBs) influence symptoms. However, the spectrum of disorders in which secondary inclusions are likely to occur has not been defined. Amygdala neurons commonly develop large numbers of secondary LBs, making it a practical region for studying this phenomenon. Objective: To characterize the spectrum of diseases associated with LB formation in the amygdala of neurodegenerative disease and control cases. Design: An autopsy series of 101 neurodegenerative disease and 34 aged control cases. Using immunohistochemistry studies, we examined the amygdala for alpha-synuclein aggregates. Results: Lewy bodies were often abundant in classic Pick disease, argyrophilic grain disease, Alzheimer disease, and dementia with LBs but not in cases with amygdala degeneration lacking tau-based inclusions, control cases, preclinical disease carriers, or degenerative diseases lacking pathologic involvement of the amygdala. The exposed alpha-synuclein epitopes were similar in all cases containing LBs. Conclusions: Abnormal alpha-synuclein aggregation in the amygdala is disease selective, but not restricted to disorders of alpha-synuclein and beta-amyloid. Our data are compatible with the notion that tau aggregates predispose neurons to develop secondary LBs.