The α-synuclein and NFL levels in plasma have been widely tested to know if they can serve as potential biomarkers to indicate PD and disease progression, whereas the results are not satisfactorily consistent (Lee et al., 2006; Ding et al., 2017; Lin et al., 2017; Chang et al., 2019; Ng et al., 2019). The gene discussed is NEFL; the disease is Parkinson disease.