The chromosome 4p16.3 region, first identified in a GWAS of familial PD [1] and subsequently replicated[3–9], represents one of the strongest disease risk loci and contains several candidate genes, including GAK, TMEM175, DGKQ, SLC26A1, and IDUA. The risk allele of the GWAS SNP at 4p16.3, rs1564282[1], was significantly associated with increased mRNA expression of the α-synuclein gene SNCA in a microarray eSNP study of PD and control cortex[10]. This evidence concerns the gene IDUA and Parkinson disease.