There is a recent effort in finding biomarkers that could provide pre-symptomatic diagnosis of PD, including single-photon emission computed tomography imaging, positron emission tomography, olfactory alterations, skin and colonic biopsy, changed metabolites, gene sequencing, and α-synuclein quantification in body fluids [188,189,190,191,192,193]. The gene discussed is SNCA; the disease is Parkinson disease.