SNCA and Parkinson disease: The abnormal and progressive neuronal deposition of the protein alpha-Synuclein (α-Syn), in the form of Lewy bodies and Lewy neurites, characterizes α-synucleinopathies that include Parkinson’s disease (PD), Parkinson’s disease dementia, and dementia with Lewy bodies, all of which share a considerable clinical and pathological overlap1.