The histological hallmark for definite diagnosis of PD is the presence of fibrillar aggregates of phosphorylated alpha-synuclein called Lewy bodies (LBs) and Lewy neurites. Previous autopsy-based studies have revealed that alpha-synuclein is deposited in the peripheral autonomic nervous system including the enteric nervous system of the alimentary tract, cardiac plexus, adrenal medulla and skin.