The Lewy pathology and aggregated α-synuclein proteins associated with PD are not confined to the central nervous system (CNS); they can also be found in the peripheral nervous system at various sites around the body, such as the skin, gastrointestinal tract, and salivary glands.1 The cause of these α-synuclein deposits is still unknown, as is the extent to which they reflect damage or loss of function in these areas.1,2 Peripheral α-synuclein pathology represents an additionally promising arena in which to explore the development of a useful biomarker of PD.2 Peripheral α-synuclein (i.e., that found outside the CNS) is easier to sample (in a skin or gut biopsy) than brain tissue.1



