Background The size of the CAG repeat tract is the major determinant of age of onset (AO) in Huntington's disease (HD). However, the number of the CAG repeats does not allow an accurate prediction of AO; only 30–70% of the variance in AO can be explained by the repeat size alone. R72P polymorphism in the TP53 gene is one of the strong candidate modifiers since this polymorphism alters the function of the p53 protein which interacts with mutant huntingtin and is involved in apoptotic cell death.

Aim We aimed to analyse the contribution of TP53 R72P polymorphisms to the AO of Turkish HD patients.

Methods DNA samples of 102 unrelated HD patients and 102 healthy age and sex matched controls were genotyped. GRIN genotyping was performed with RFLP analysis. Hardy–Weinberg test statistics were computed for each SNP. The odds ratios and independent sample t tests for genotypes were computed for association of genotypes with AO.

Results We demonstrated that TP53 R72P polymorphism can explain 2.9% of the variation observed in onset age and 4.98% of the variation that is not attributable to CAG repeat size in our population.

Conclusions An association between the TP53 R72P polymorphism and AO of Indian HD patients was recently reported. However, the following replication studies could not confirm this result. In this study, we presented supporting data for the original investigation and demonstrated that the TP53 gene can be regarded as a modifier for Turkish HD patients.