SNCA and Parkinson disease: PD is classified as an α-synucleinopathy [39, 56, 83, 120, 132, 158, 187, 193, 227, 249], a group of disorders characterized by the central accumulation and spread of α-synuclein (α-syn) in the form of Lewy pathology (LP), including Lewy bodies (LBs) and Lewy neurites (LNs) [61, 83, 120, 193, 227, 249].