Studies have shown that many non-motor symptoms of PD, such as constipation, autonomic dysfunction, etc., may be related to the pathological deposition of α-synuclein in the peripheral nervous system (PNS) (Visanji et al., 2013; Borghammer et al., 2016; Borghammer, 2018). The gene discussed is SNCA; the disease is Parkinson disease.