The hallmark pathology of Lewy body diseases (LBDs), including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB), is the intraneuronal accumulation of alpha-synuclein (aSyn) in inclusions known as Lewy bodies (LBs) and Lewy neurites (LNs). The gene discussed is SNCA; the disease is Parkinson disease.