It has been hypothesized that the periphery of the body could be an early indicator of PD onset, as it has been observed that, as previously stated, phosphorylated alpha-synuclein aggregates can travel between neurons and are not only found in the central nervous system but also within the olfactory bulb and in the peripheral autonomic nervous system of the upper aerodigestive [67] and gastrointestinal tracts [68]. The gene discussed is SNCA; the disease is Parkinson disease.