Today, the role of α-synuclein in PD is still contended, the debate as to potential neuroprotective or toxic roles is well-considered [123], however there is overwhelming evidence that Lewy pathology is unlikely to be benign [124], and there is increasing acceptance in the field that PD can be classified as a prionoid disorder, driven by the spread, seeding and aggregation of misfolded α-synuclein [125, 126]. Here, SNCA is linked to Parkinson disease.