Tremor in Parkinson's disease is not associated with the DRD3 Ser9Gly polymorphism.

A common subset of genetic risk factors for Parkinson's disease (PD) and essential tremor (ET) has been postulated. Recently, an association between the dopamine D(3) receptor (DRD3) Ser9Gly polymorphism and ET has been reported. We studied whether PD tremor is influenced by Ser9Gly in a genetic association study based on the gene bank of the German Competence Network on Parkinson's disease. The study included analyses of motor predominance (mixed, hypokinetic, and tremor), and tremor type (resting, postural, and action). We did not identify any effect of DRD3 Ser9Gly on tremor in PD, even when regarding various symptom combinations to avoid missing a weak effect on the phenotype. Additional studies incorporating symptoms at disease onset, and grading of tremor response to dopaminergic therapy, are warranted.