SNCA and Parkinson disease: Parkinson’s disease (PD) is themost common neurodegenerativemovement disorder and the most common synucleinopathy.1−4 Synucleinopathies are a diverse class of neurodegenerative diseasesthat also include multiple system atrophy (MSA) and dementia withLewy bodies (DLB).5−8 These diseases are characterized by the formation of fibrillar aggregatesof the protein α-synuclein (αSyn) in the brain.