The neuropathological changes that underlie the clinical PD spectrum are subtyped as PD, dementia with Lewy bodies (DLB), and Parkinson’s disease dementia (PDD); they are characterized by the formation of intracellular protein inclusions and immunoreactive for alpha-synuclein (α-syn) and its pathological forms such as phosphorylated S129 α-syn [39,98]. This evidence concerns the gene SNCA and Parkinson disease.