Objective: Urolithiasis has a strong familial component. However, to date, no specific genetic abnormality has been identified. It has been reported that allelic variation in the vitamin D receptor (VDR) gene may affect calcium absorption and excretion. Urolithiasis is a multifactorial disease in which both genetic and environmental factors have an effect on onset and severity of disease. In the present study, the role of Taq I polymorphism of vitamin D receptor gene in urolithiasis was studied.
Methods: Eighty children with calcium stone disease (40 with single episode of stone disease and 40 with recurrence) and 40 controls were enrolled. Polymorphic sites were amplified by polymerase chain reaction, digested with Taq I restriction enzymes and analyzed by gel electrophoresis. Allelic or genotypic frequencies were calculated and associations between them and the presence of hypercalciuria, family history and stone recurrence were evaluated.
Results: Incidence of Taq I tt genotypes was significantly higher in patients with recurrent calcium-stone disease compared to the controls. In addition, the frequency of the 't' allele was higher in recurrent calcium-stone formers. Taq I t allele was found to be associated with increased risk of recurrence. No association between Taq I polymorphism and a positive family history was found in the present study. The frequency of hypercalciuria was higher in patients with the 'tt' genotype.
Conclusion: Taq I t allele of the VDR gene may be a risk factor for severe urolithiasis and recurrent stone disease.