The frequency of allele T positivity (CT+TT vs CC) showed a significant association between HNMT rs11558538 and the risk for PD, both in the total series and in the series confined to Caucasian populations (Table 2; Fig. 2A and B), whereas homozygosity (TT vs CC+CT) did not show association (Table 2; Fig. 3A and B). This evidence concerns the gene HNMT and Parkinson disease.