Iliac bone histomorphometry in children with newly diagnosed inflammatory bowel disease

Children with inflammatory bowel disease (IBD) manifest low bone mass; the cause remains unclear. We performed transilial bone biopsies in 20 IBD children at diagnosis and found a mild cortical bone deficit and slow bone turnover. It is possible that low mechanical stimulation due to inadequate muscle mass contributes to the bone deficit. Children with newly diagnosed IBD can have low bone mineral density and disturbed bone metabolism, but the tissue level characteristics of the bone involvement in pediatric IBD have not been elucidated. In the present study, we evaluated the skeletal status, including static histomorphometry on transiliac bone samples, in 20 patients (age range 8.4 to 17.7 years, 12 boys) with newly diagnosed IBD and compared results to published normative data. Despite normal height (mean Z-score 0.04, SD 1.2), areal bone mineral density at the lumbar spine was moderately low (mean age- and sex-specific Z-score -0.8, SD 1.1). Total body bone mineral content and lean mass were low for age and sex as well (mean Z-scores -1.2, SD 0.9 and -2.0, SD 0.9, respectively). Biochemical bone markers indicated low bone formation and resorption activity. Bone histomorphometry revealed a slightly low cortical width (mean 23%, SD 25%, below the result expected for age) but a normal amount of trabecular bone. The percentage of trabecular bone surface covered by osteoid or osteoclasts was low, suggesting that both bone formation and bone resorption were suppressed. Our results indicate that young patients manifest a mild cortical bone deficit at the iliac crest and slow trabecular bone turnover even at diagnosis, in the setting of IBD.