Association of vitamin D receptor gene polymorphism with urolithiasis

Purpose: Recent studies suggest that allelic variations of the vitamin D receptor (VDR) gene can influence calcium absorption and excretion. Therefore, we studied the association of VDR gene polymorphism with urolithiasis. Subjects and Methods: We studied 83 patients with urinary stones and 83 controls. Patients were scored for certain clinical characteristics, including long axis diameter of the largest stone (11 point-less than 10 mm. and 2-10 mm. or greater), number of stones (1 point-1 and 2-multiple) and history of calcium stone disease (1 point-absent and 2-present). They were classified into 3 groups according to the total score, including low-3, intermediate-4 or 5 and high-6 points. The 2 VDR gene polymorphisms TaqI and ApaI were detected by polymerase chain reaction-restriction fragment length polymorphism and their relationships with the urinary calcium level were examined. Results: The incidence of TaqI Tt and tt genotypes was significantly higher in the high score group than in controls. The TaqI t allele was associated with a 5.2-fold increase in the risk of severe stone disease. The urinary calcium level in patients with the Tt and tt genotypes was also higher than in those with the TT genotype. The rate of the ApaI genotype was not different in the high score group and controls. Conclusions: The TaqI t allele of the VDR gene may be a risk factor for severe stone disease and recurrent stones.