Background: The bone mass deficit in pediatric Crohns disease (CD) is associated with low total body lean mass and suppression of bone turnover.
Objective and hypotheses: We examined at diagnosis whether the sarcopenia is associated with leg muscle hypofunction, changes in tibia musclebone indices as well as overt bone strength loss (vertebral fractures, VF).
Method: 70% children with CD were studied within 2 weeks of diagnosis (64% boys; median age 13.9 years, range 717) including lateral spine radiograph for VF assessment by the Genant semi-quantitative and Algorithm-Based Qualitative methods. Muscle function was measured by peak jump power (PJP) on a two-legged jump by mechanography force plate. Musclebone structural indices were measured by peripheral quantitative computed tomography (pQCT) at 4, 38 and 66% tibia sites. PJP and pQCT results were converted to age-, gender- and tibia-length specific Z-scores (as appropriate).
Results: 90% of children had moderate or severe CD, 36% were pre-pubertal, height and weight Z-scores were low (mean±S.D. −0.3±1.1, P=0.046 and −0.8±1.3, P<0.001, both compared to the healthy average). Only one patient had VF (1%, 95% CI 0, 4) a 16-year-old boy with severe CD and VF at T4/5 plus loss of end-plate parallelism at T12/L1. The following musclebone indices were reduced: PJP (Watts/kg, mean Z-score −1.9±1.6, P<0.001), tibia trabecular density (−1.4±1.4, P<0.001), cortical bone mineral content (BMC) (−0.9±1.2, P<0.001) and muscle cross-sectional area (−1.5±1.1, P<0.001). Cortical density at 38% was preserved (mean 0.2±1.1, P=0.171).
Conclusion: Leg muscle mass and dynamic function is reduced in newly diagnosed CD children. The tibia findings including low trabecular density, low cortical BMC but relative preservation of cortical bone density suggest a relatively recent insult affecting muscle and development. The VF prevalence, while low, highlights that children with CD at diagnosis are not exempt from overt bone strength loss.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology