Substantial evidence suggests that missense point mutations (such as A53T, A30P, and E46K) or duplications in the α-syn-encoding SNCA gene lead to autosomal-dominant early-onset PD (Polymeropoulos et al., 1997; Kruger et al., 1998; Zarranz et al., 2004). The gene discussed is SNCA; the disease is Parkinson disease.