SNCA and Parkinson disease: In a recent small, preliminary study on 78 patients with iRBD of which 16 converted to PD after 3.75 years, hypomethylation at the Cytosine-phosphate-Guanine (CpG) 17 of the SNCA intron 1 has been associated with increased risk of clinical phenoconversion, and hypomethylation to the CpG 14, 15, and 16 was associated with progression of iRBD symptoms [32•].