Background VDR gene polymorphism has been associated with variations in bone mineral density (BMD) in normal populations, most studies linking the presence of the Bsm-1 restriction site (b) with higher BMD as compared to absence of Bsm-1 restriction site (B). We found that in steroid induced osteoporosis in PMR patients there is an overrepresentation of bb and that in normal controls, higher BMD is found in Bb heterozygotes (FA Gidden: data submitted).
Objectives To investigate the VDR gene polymorphism frequency and association with BMD in newly diagnosed patients with PMR, prior to treatment with corticosteroids.
Methods Thirty patients with active PMR (fulfilling Bird’s criteria), consecutively referred by GP’s to the PMR clinic, underwent lumbar spine and hip BMD scanning on a Hologic dual X-ray absorptiometer (DXA). 5 ml EDTA blood was obtained from each patient and used for DNA extraction. Polymerase chain reaction (PCR) and agarose gel electrophoresis were used for Bsm-1 site typing.
Results The VDR genotype distribution was: BB in 6 patients (20%), Bb in 10 patients (33.3%) and bb in 14 patients (46.7%). Mean BMD of lumbar spine (L1-L4) expressed as Z-score was in BB group 0.32 (95% CI: -0.47–1.11), in Bb group 1.37 (95% CI: 0.31–2.41) and in bb group 0.46 (95% CI: -0.25–1.18). Mean BMD of femoral neck (Z-score) was in BB group -0.05 (95% CI: -1.5–1.39), in Bb group 0.49 (95% CI: -0.24–1.23) and in bb group 0.13 (95% CI: -0.39–0.65). Mean age of patients was 73.6, SD 7.6. There was no statistically significant difference between groups with regard to age, disease duration and disease activity (measured by ESR, CRP, Pain Visual Analogue Score, Global Disease Activity Score and Health Assessment Questionnaire).
Conclusion There is an overrepresentation of bb in PMR patients (as compared to UK VDR frequencies: BB 20.5%, Bb 49.7%, bb 29.8%)1 which may reflect VDR polymorphism role in susceptibility to inflammatory conditions e.g. PMR. Heterozygotes Bb have highest BMD. Bb genotype may be bone protective for steroid induced osteoporosis.
Houston LA, et al. Bone 1996;18(3):249–52
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