In Parkinson's disease and dementia with Lewy bodies, neuronal α-synuclein aggregates (Lewy bodies and Lewy neurites) are distributed throughout the nervous system, including the brain, spinal cord, sympathetic ganglia, enteric nervous system, cardiac and pelvic plexuses, submandibular gland, adrenal medulla, and skin. Lewy bodies also occur in 10-20% of neurologically asymptomatic individuals older than 60 years. These cases are called incidental Lewy body disease (ILBD). In ILBD, Lewy bodies can be found in the brain, spinal cord, sympathetic ganglia, visceral autonomic nervous system and skin. In addition, neuronal loss in the substantia nigra is observed in ILBD. Thus, ILBD represents pre-symptomatic Parkinson's disease and/or dementia with Lewy bodies. The pathological process of Lewy body disease may affect the peripheral and central nervous systems at the same time.