A genome-wide methylation analysis of PD with quantitative DNA methylation levels of 27,500 CpG sites corresponding to 14,495 genes showed a significant methylation decrease of the CYP2E1 gene with the corresponding mRNA overexpression in brains from PD patients, suggesting that epigenetic variants of this cytochrome contribute to PD susceptibility [257] (Table 2). Here, CYP2E1 is linked to Parkinson disease.