The progressive accumulation of α-synuclein neurotoxic species (i.e., oligomers, protofibrils and fibrils) in the SNpc characterize PD as a synucleinopathy, a disease category that includes other neurodegenerative disorders such as dementia with Lewy bodies (DLB), in which α-synuclein aggregates accumulate mostly in the frontal cortex, and multiple system atrophy (MSA), in which they accumulate in oligodendrocytes, forming glial cytoplasmic inclusions [18]. The gene discussed is SNCA; the disease is Parkinson disease.