SNCA and Parkinson disease: Although it is true that mutations in α-synuclein and triplication of its gene (SNCA) are causative (Polymeropoulos et al., 1997; Singleton et al., 2003), they do not necessarily trigger disease onset significantly in advance of the onset of idiopathic PD (>60 years of age), unlike what is seen with Parkin-mediated PD (< 40 years of age).