S100A9 and Parkinson disease: Previous studies also report that genetic variants may have regional effects beyond a single gene, so further studies of rs10888557 loci in the context of PD should include an analysis of other SNPs and structural variations (i.e., in non-coding regions) within the region of PGLYRP4 and S100A9 genes in order to investigate and potentially establish the extent of association (Roses et al., 2016; Theunissen et al., 2020).