| Background. Children with sickle cell disease type SS (SCD-SS) have several risk factors for poor bone mineralization, including malnutrition, endocrine disturbances and reduced physical activity. However, bone mineral deficits in this population have not been well characterized.;Methods. Three studies were performed to investigate bone status in a cohort of sixty-five children with SCD-SS ages 5 to 18 years from The Comprehensive Sickle Cell Center at The Children's Hospital of Philadelphia, with reference data obtained from healthy African-American children recruited concurrently. Bone mineral content (BMC) in the whole body (WB) and lumbar spine (LS) were measured by dual energy x-ray absorptiometry (DXA). Peripheral quantitative computed tomography (pQCT) was used to determine volumetric bone mineral density (vBMD), geometric properties, cross-sectional moment of inertia (CSMI) and strain strength index (SSI). Vitamin D status was determined by serum 25 hydroxyvitamin D [25(OH)D] concentrations. Dietary intake of vitamin D and calcium was estimated by three 24-hour recalls.;Results. Children with SCD-SS had reduced height-for-age, weight-for-age and WB BMC-for-age z-scores. After adjusting for height, WB BMC deficits were eliminated. In contrast, in the LS both BMC-for-age and BMC-for-height z-scores were reduced in children with SCD-SS. While trabecular and cortical vBMD did not differ between subjects and controls, CSMI and SSI, measures of bone strength, were significantly reduced in children with SCD-SS. Dietary intake of calcium and vitamin D was suboptimal in both groups. Logistic regression analysis indicated that the odds for vitamin D deficiency among subjects with SCD-SS were 9.5 (95% CI: 3.0, 29.6) times greater than among the controls after adjusting for season and age.;Conclusions. Children with SCD-SS had size-adjusted deficits in LS BMC but not in WB BMC. No deficits in vBMD of the tibia were observed in children with SCD-SS, although measures of bone strength were reduced. Finally, a significantly higher risk of vitamin D deficiency was found in children with SCD-SS, which may lead to impaired calcium absorption. Future studies in children with SCD-SS should include interventions to improve vitamin D and calcium intake in order to determine their impact on linear growth, calcium absorption, bone mineralization and bone strength. |
