Alpha-synuclein forms the major component of Lewy bodies and Lewy neurites, the 
defining neuropathological characteristics of Parkinson's disease and dementia 
with Lewy bodies. Here we show that alpha-synuclein is also the major component 
of the filamentous inclusions of multiple system atrophy which comprises several 
neurodegenerative diseases with a shared filamentous pathology in nerve cells 
and glial cells. These findings provide an unexpected link between multiple 
system atrophy and Lewy body disorders and establish that 
alpha-synucleinopathies constitute a major class of human neurodegenerative 
disorder.