DHCR7 and Parkinson disease: Alaylıoğlu et al. demonstrated that although DHCR7/NADSYN1 and CYP2R1 gene variants were not associated with serum 25(OH)D3 levels or PD risk, specific SNPs in these loci correlated with milder motor symptoms, shorter disease duration, and reduced incidence of freezing of gait and falls [192].