COMT and Parkinson disease: More importantly, in the present study, in addition to the detrimental effect of COMT rs4680(A) on the motor symptoms of PD patients, we also found that ALDH2 rs671 SNP moderates the impact of COMT rs4680(A) for the symptom of “hand movements.” The negative effect of rs4680(A) on PD patients’ hand movements is more pronounced in the presence of genotype rs671(GG).