Compared with subjects with the CC or CA genotype of UCHL1  S18Y and the CC or CT genotype of SNCA SNP rs356220, those with the AA genotype of UCHL1  S18Y and the TT genotype of SNP rs356220 had a significantly increased risk of sporadic PD; the interaction, however, was not significant. Here, UCHL1 is linked to Parkinson disease.