Copy number variations, such as duplication or triplications of the SNCA gene encoding for α-synuclein, as well as point mutations and single nucleotide polymorphisms (SNPs) cause PD and DLB or increase the risk of developing the disease (Singleton et al., 2003; Chartier-Harlin et al., 2004; Zarranz et al., 2004; Nalls et al., 2014; Orme et al., 2018). The gene discussed is SNCA; the disease is Lewy body dementia.