Association of a dopamine D2 receptor gene polymorphism with levodopa-induced dyskinesias in Parkinson's disease

Genetic factors could have a role in determining the occurrence of levodopa-induced peak-dose dyskinesias in Parkinson's disease (PD), since a substantial proportion of patients never develop peak-dose dyskinesias. To investigate whether an intronic short-tandem repeat (STR) polymorphism in the gene for the dopamine receptor D2 (DRD2) is associated with the risk of developing peak-dose dyskinesias in PD, we performed a case-control study of 136 subjects with sporadic PD and 224 population control subjects. The 15 allele of the STR polymorphism of the DRD2 gene was more frequent in parkinsonian subjects than in controls. Moreover, the frequency of both alleles 13 and 14 was higher in nondyskinetic than in dyskinetic PD subjects. The risk reduction of developing peak-dose dyskinesias for PD subjects carrying at least one of the 13 or 14 alleles was 72% with respect to the PD subjects who did not carry these alleles. The present results indicate that certain alleles of the STR polymorphism of the DRD2 gene reduce the risk of developing peak-dose dyskinesias.