BONE MINERAL DENSITY AND VITAMIN D RECEPTOR GENETIC VARIANTS IN EGYPTIAN CHILDREN WITH BETA THALASSEMIA ON VITAMIN D SUPPLEMENTATION

Abstract

Background: Low bone mineral density (BMD) is a characteristic feature of Beta thalassemia major (βTM) patients. Vitamin D is important for bone mineralization. Vitamin D receptors (VDR) genetic variants may be related to vitamin D status and BMD. Objectives: To evaluate the effect of VDR genetic variants on vitamin D levels and BMD in βTM Egyptian patients supplemented with vitamin D. Methods: This study was conducted on forty children with βTM and forty unrelated healthy sex and age-matched controls. Serum calcium, phosphorus, ALP, ferritin and vitamin D were measured. VDR genetic variants (BsmI, TaqI, and FokI) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). BMD was measured by dual-energy X-ray densitometry (DEXA) of the lumbar spine. Results: In βTM patients, 22.5% had deficient, 50% had insufficient and only 27.5% had sufficient levels of vitamin D. BMD Z score was significantly lower in βTM patients compared to controls (p<0.001). Osteopenia and osteoporosis of lumbar spines were observed in 70% and 22.5% of βTM patients respectively. BsmI bb and FokI Ff and ff genotypic variants were significantly associated with lower vitamin D and BMD Z score. No association was observed with TaqI genotypic variants. Conclusions: We reported a high prevalence of low BMD in βTM despite vitamin D supplementation. The BsmI bb, FokI Ff and ff genotypic variants of VDR can be considered as risk factors for the occurrence of osteoporosis in these children. Vitamin D doses should be adjusted individually according to the genetic makeup of each patient.

Keywords

• Vitamin D
• VDR genetic variants
• BMD
• Osteoporosis
• DEXA
• Thalassemia.