SNCA and Parkinson disease: For example, alpha-synuclein (α-Syn, SNCA) is now thought to mediate neurotoxicity not only in Parkinson’s disease (PD), but also in Parkinson’s Disease Dementia (PDD) and Lewy Body Dementia (LBD) where it accumulates in Lewy bodies (Spillantini et al., 1997).