Background: Thalassaemia major (TM) is a condition of ineffective erythropoiesis requiring chronic transfusions and iron chelation to reduce end-organ complications. Bone disease is common, with marrow expansion and endocrinopathies contributing to low bone mineral density (BMD) and fractures. Recent work demonstrating renal tubulopathy, hypercalciuria, and kidney stones identified a new mechanism of bone loss in TM (1). Trabecular bone score (TBS), derived from lumbar dual-energy X-ray absorptiometry (DXA) images, provides surrogate measures of bone microarchitecture, but its role in TM renal-bone disease is unknown.
Methods: Retrospective cross-sectional study of 71 patients (>18 years) with TM. TBS reference ranges for Australian men and women were obtained from the Geelong Osteoporosis Study (2). Clinical, biochemical and DXA parameters were documented; patients treated with hydrochlorothiazide were excluded.
Results: 71 patients with TM were identified (mean age 44.5 ± 10 years; 42% male): fragility fractures occurred in 20/71 (28%) and predominantly involved the distal radius and vertebra. Males had lower lumbar spine (LS) and femoral neck (FN) BMD Z-scores (-1.70 ± 1.2; -1.11 ± 1.2) than females (-1.48 ± 1.4; -1.09 ± 0.9). TBS values were reduced compared with aged matched controls (2), male: 1.24 ± 0.13 (normal 1.29 ± 0.11) and female: 1.19 ± 0.12 (normal 1.38 ± 0.11). Degraded or partially degraded TBS values were identified in 19/30 (63%) of males and 32/41 (78%) of females. LS and FN Z-scores were significantly associated with fractures (P<0.05) but TBS was not.
Urine calcium/creatinine ratios were elevated 0.95 (0.05 to 9.1) (normal <0.5) and renal calculi were highly prevalent (40.6%). Renal calculi were associated with non-vertebral fractures (P=0.03) and TBS (P=0.006) after adjusting for urine calcium/creatinine. Conventional DXA parameters were not associated with renal calculi.
Conclusion: Reduced TBS is common in TM. The significant association between kidney stones and TBS deserves further study.