LRRK2 and Parkinson disease: The highly similar methylation modification patterns in brain and peripheral blood suggest that peripheral blood may be an effective proxy for brain methylation levels.[16] Previous studies have suggested that SNCA and LRRK2 hypomethylation in peripheral leukocytes can be used as potential biomarkers for early diagnosis of PD.[16] In addition, miRNAs obtained from serum, plasma, and circulating blood cells have also been proposed as possible PD biomarkers.[17] However, there are also some difficulties in the current study of PD epigenetic biomarkers.