Zhang et al. [6] showed that the frequency of the Y allele of UCHL1  S18Y SNP was significantly higher among control subjects than among PD patients in a Japanese population (crude OR = 0.73 [95 % CI: 0.53 − 0.99]), whereas, under a recessive model, the AA genotype was non-significantly positively associated with the risk of sporadic PD in a Caucasian population (crude OR = 4.76 [95 % CI: 0.52 − 226.8]); furthermore, the frequency of the AA genotype was much lower among Caucasians than among Japanese. The gene discussed is UCHL1; the disease is Parkinson disease.