SNCA and Lewy body dementia: Lewy body spectrum disorders (LBSD), including PD with and without cognitive impairment, Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) as well as multiple system atrophy (MSA) are classified as α-synucleinopathies due to the presence of misfolded α-synuclein aggregates.