Promising biomarker candidates for early diagnosis of PD that have emerged are: alpha-synuclein species (total α-syn, oligomeric α-syn and phosphorylated α-syn), β-amyloid 1–42, axonal damage markers (tau, neurofilament light (NfL)) and lysosomal enzymes [9,10,11]. Here, SNCA is linked to Parkinson disease.