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Keywords:

  • sickle cell disease;
  • bone mineral density;
  • vitamin D

Abstract

Objectives:  To assess the prevalence in children with sickle cell disease of low bone mineral density (BMD), a feature found in up to 82% of adults but not well known in children.

Methods:  In 53 children (45 SS, 4 SC, 4 Sβ-thalassemia) with a mean age of 12.8 ± 2.4 years, we assessed height; weight; sexual maturation; number of hospitalizations, painful crises, and transfusions in the last 3 years; calcium intake; steady-state hemoglobin and leukocyte count; calcaemia, phosphataemia, and calciuria/creatinuria; serum 25-(OH)D and PTH concentrations; and osteocalcin, urinary deoxypyridinoline, and the C-terminal component of pro-collagen type I. BMD was assessed using dual X-ray absorptiometry.

Results:  Mean lumbar spine Z-score was −1.1 ± 1.3 (−3.9 to +1.8). The Z score was significantly lower in girls than in boys in the prepubertal subgroup (−1.74 ± 0.27 vs. −0.53 ± 0.31) (= 0.0169), but not in the pubertal group (−1.15 ± 0.41 vs. −1.33 ± 0.70). BMD was not associated with any of the disease-severity markers in girls but was unexpectedly associated with fewer vaso-occlusive crises and hospitalizations in boys. BMD did not correlate with hemoglobin or leukocyte counts. Vitamin D deficiency [25-(OH)D < 12 ng/mL] was found in 76% of patients and secondary hyperparathyroidism (PTH > 46 pg/mL) in 38%. BMD was not related to calcium intake, vitamin D status, osteocalcin, or bone resorption markers.

Conclusion:  A slight BMD decrease was found in SCD children, starting before puberty and being more marked in females. The decrease was unrelated to disease severity, vitamin D deficiency, or bone hyperresorption, suggesting abnormal bone formation as the underlying mechanism.