SNCA and Parkinson disease: Dermal nerve fibers (111, 112), cerebrospinal fluid (113), submandibular glands (114), colonic submucosal nerve fibers (115), salivary glands (116), and parotid glands (117) have all been found to contain pathological α-synuclein proteins in idiopathic RBD patient populations and confirmatory PD populations.