Skin biopsy for α-synuclein immunohistochemistry and assessment of nerve fiber density is now commercialized based on high sensitivity and specificity to distinguish synucleinopathy from other proteinopathies [34], with alpha-synuclein deposition predominating in somatosensory versus sympathetic adrenergic fibers in MSA versus PD, respectively [35, 36]. This evidence concerns the gene SNCA and Parkinson disease.