SNCA and Parkinson disease: Although less explored than common single-nucleotide variants (SNVs), copy number variants (CNVs) have been reported, especially in PD-associated genes where pathogenic deletions and duplications have been identified using either a gene candidate approach (PRKN, SNCA, PINK1, PARK7 and ATP13A2) (Toft and Ross, 2010; Pankratz et al., 2011; La Cognata et al., 2017) or genome-wide burden analysis (Liu et al., 2013; Sarihan et al., 2021).