Status of 25-hydroxyvitamin D deficiency and effect of vitamin D receptor gene polymorphisms on bone mineral density in thalassemia patients of North India

Background: Bone disease comprising of low bone mineral density (BMD), bone pain, and fractures is a characteristic feature of thalassemia. Vitamin D receptors (VDRs - FokI, TaqI, and BsmI) polymorphisms are closely related to low BMD at the lumbar spine and hips which can be used as a useful genetic marker in predicting bone disease in these patients. Aim: To find out the status of VDRs gene polymorphisms and its effect on osteoporosis in thalassemia patients of North Indian origin. Material and methods: BMD was measured in 40 beta-thalassemia major patients by dual-energy X-ray densitometry (DXA). Serum vitamin D levels were estimated by enzyme linked immunosorbant assay. VDR gene polymorphisms (FokI, TaqI, and BsmI) were analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method. Results: About 80.6% cases were found to be vitamin D deficient. Z score of BMD of lumbar spine and hips were -2.31 +/- 1.18 and -2.09 +/- 0.89. Osteoporotic lumbar spine was observed in 42.5% cases of thalassemia. A positive correlation of vitamin D level was found with Z score of BMD of lumbar spine (r = 0.398, P value = 0.027). Polymorphisms of FokI and BsmI were found significantly correlated with BMD of lumbar spine. However, no association of BMD was observed with TaqI polymorphism. Conclusion: The present study showed a high prevalence of low BMD in thalassemia, suggesting that they should be targeted for DXA screening and osteoporosis prevention before permanent end organ bone damage occurs. The VDR genotyping can be used as additional test in individuals who are susceptible to osteoporosis so that early preventive measurements can be taken.