Although most PD patients have a sporadic disease, recent studies identified several familial PD-related genes including SNCA (encoding α-syn protein), UCH-L1 (encoding ubiquitin C-terminal hydrolase-like 1 protein), PRKN (encoding parkin protein), LRRK 2 (encoding leucine-rich repeat kinase 2 protein), PINK 1 (encoding PTEN-induced kinase protein), and DJ-1 (encoding DJ-1 protein) [25]. Here, UCHL1 is linked to Parkinson disease.