Furthermore, alpha-synuclein aggregation and phosphorylation throughout the enteric nervous system have been reported in people with PD (Braak et al., 2006) sometimes up to 20 years before PD diagnosis (Stokholm et al., 2016), but are not specific to PD (Visanji et al., 2015; Corbillé et al., 2016). This evidence concerns the gene SNCA and Parkinson disease.