SNCA and Parkinson disease: Lewy body disorders (LBD) are pathologically characterized by abnormal accumulations of alpha‐synuclein (SYN) in Lewy bodies and Lewy neurites which are found in a clinically and pathologically heterogeneous group of neurodegenerative diseases, including Parkinson’s disease (PD), PD with dementia (PDD), and dementia with Lewy bodies (DLB).1