Longitudinal study of bone mineral density in children after a diagnosis of Crohn's disease

The purpose of this study was to measure the bone mineral density (BMD) of children with Crohn's disease (CD) and to prospectively assess its evolution. A total of 27 children (20 boys, seven girls), aged 12.1 ± 2.5 years, were recruited at the time of CD diagnosis. Dual-energy X-ray absorptiometry (DEXA) was used to measure BMD, expressed as Z scores for chronological age (BMD/CA) and bone age (BMD/BA). One year later, BMD was measured again to identify any correlations with disease activity [group A (active disease) vs group R (remission)]. BMD/CA and BMD/BA were negatively correlated with delay in diagnosis ( P < 0.0001 and P < 0.05, respectively). BMD/CA was less than −2 standard deviation (SD) in nine patients and BMD/BA was less −2 SD in four patients. At the follow-up, the increase in BMD was smaller in group A ( n = 14), whether expressed as absolute values (−0.002 vs 0.040 g/cm 2 per year; P < 0.024) or as percentages (−0.2 vs 6.6%; P < 0.041); changes in BMD/CA (−0.5 vs −0.1 SD/year) and BMD/BA (−0.3 vs 0 SD/year) did not differ. Diagnostic delay greatly affects BMD in children with CD even prior to corticosteroid therapy. The risk of low BMD increases with persistent CD activity, although the risk is reduced in association with bone maturation delay.