To date, six missense mutations in the SNCA gene and the occurrence of gene multiplication have been identified in familial forms of PD and DLB (Polymeropoulos et al., 1997; Kruger et al., 1998; Singleton et al., 2003; Chartier-Harlin et al., 2004; Ibanez et al., 2004; Zarranz et al., 2004; Appel-Cresswell et al., 2013; Lesage et al., 2013). The gene discussed is SNCA; the disease is Lewy body dementia.