Assuming that environmental factors may have a larger impact on sporadic PD development compared to familial PD, it is surprising that no difference is found between sporadic PD and LRRK2 patients heterozygous for a LRRK2 mutation either in the methylation status of islands of the LRRK2 promoter in patient derived leucocytes (Fernandez-Santiago et al., 2015) or when investigating whole genome methylation of dopaminergic neurons generated from patient derived induced pluripotent stem cells (iPSCs). The gene discussed is LRRK2; the disease is Parkinson disease.