BONE MINERAL DENSITY AND VITAMIN D RECEPTOR POLYMORPHISM IN β-THALASSEMIA MAJOR

Abstract

Osteoporosis is the most prevalent bone complication in β-thalassemic patients despite regular transfusions and iron chelation therapy. Although its etiology is multi-factorial, genetic factors play an important role in pathogenesis. These factors have not yet been clearly defined, however, osteoporosis may be related to vitamin D receptor gene BsmI polymorphism. In this study, BsmI vitamin D receptor gene polymorphism was analyzed using polymerase chain reaction and BsmI restriction fragment length polymorphism in 42 regularly treated- βthalassemic patients of different ages. Bone mineral density was measured by peripheral quantitative ultrasound at the heel of the foot. Serum levels of alkaline phosphatase, calcium, phosphorus, ferritin and 25hydroxyvitamin D3 were determined. Patients were divided into two groups according to pubertal signs: group I (22 children), and group II (20 adolescents and adults). The Z-scores of bone mineral density in both groups were -1.32 ± -0.9 and -2.30 ± -1.02 respectively, with a significant difference between the two groups. The height standard deviation and 25-hydroxyvitamin D3 were significantly decreased in group II compared to group I. Moreover, significantly lower bone mineral density and height standard deviation were detected among patients with BB vitamin D receptor genotype. Therefore, this genotype may be considered as a risk factor for osteoporosis in β-thalassemic patients.