Bone Mineral Density and Vitamin D Receptor Genetic Variants in Egyptian Children with Beta Thalassemia Major on Vitamin D Supplementation

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 seventeen unrelated healthy sex and age-matched controls. Serum calcium, phosphorus, alkaline phosphatase, 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 insufficient, and 77.5% had sufficient levels of vitamin D, and no cases had vitamin D deficient. 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: Low BMD is prevalent in patients with 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.