CYP27A1 and Parkinson disease: Further analyzing the occurrence of SNPs in the corresponding P450, we observed that nearly 80% (79.3%) of the IPD patients had at least one PD-associated SNP in the CYP46A1, CYP7B1, CYP39A1 or CYP27A1 genes (75 out of 362 IPD patients did not show any associated SNP in these four genes) compared to 70% of HC (Table 3).