Vitamin D receptor gene polymorphism and calcium metabolism in sarcoidosis patients.

Background: Hypercalcemia has been recognized as an important complication of sarcoidosis, caused by overproduction of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) at sites of granulomatous reactions. Polymorphism of the vitamin D receptor (VDR) gene has recently been shown to be related to bone mineral density, and also associated with hyperparathyroidism and risk of granulomatous disease. In light of the possible impact on hypercalcemia of sarcoidosis, an investigation of calcium metabolism and polymorphism of the VDR gene in sarcoidosis patients was carried out.

Methods: Genotypes were determined using the polymerase chain reaction and restriction fragment length polymorphism. Maximum calcium, 1,25(OH)2D3, and intact PTH levels were also determined.

Results: Depressed PTH levels were found in sarcoidosis patients, especially in those with the bb genotype, but there was no difference in 1,25(OH)2D3 levels among the VDR genotypes, and this polymorphism also had no association with onset of hypercalcemia.

Conclusion: From these results, we speculate that although the VDR gene polymorphism may affect the serum PTH level, it is not a risk factor for hypercalcemia in sarcoidosis.