Parkinson's disease (PD) is the second-most common neurodegenerative disorder caused by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and the presence of ubiquitinated alpha-synuclein- (α-syn-) containing cytoplasmic inclusions called Lewy bodies in surviving SNpc neurons [62]. The gene discussed is SNCA; the disease is Parkinson disease.