Considering its relation to other risk factors for conversion from RBD to PD such as hyposmia and reduced FP-CIT dopamine transporter uptake, p-alpha-syn deposition in skin may be used in RBD patients as a peripheral histopathological marker of an alpha-synucleinopathy, prior to the onset of PD motor symptoms. This evidence concerns the gene SLC6A3 and Parkinson disease.