Bone mineral density and vitamin D receptor polymorphism in beta-thalassemia major

Osteoporosis is the most prevalent bone complication in beta-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-beta-thalassemic 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 25-hydroxyvitamin 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 beta-thalassemic patients.