Low bone mineral density in Crohn's disease, but not in ulcerative colitis, at diagnosis

The pathogenesis of low bone mineral density in patients with inflammatory bowel disease is unclear, and the relevance of secondary osteopenic influences is controversial. Our aim was to study bone mineral density in newly diagnosed patients.

Bone mineral density and biochemical parameters of bone metabolism were measured in 15 patients with Crohn's disease and 15 patients with ulcerative colitis, all of whom were newly diagnosed. Lumbar and forearm bone mineral densities were measured by dual energy x-ray absorptiometry, and Z scores were obtained by comparison with age- and sex-matched normal values. Twenty-three patients had repeat measurements 1 year later, and 20 had received systemic steroids.

At diagnosis, the mean Z score for patients with Crohn's disease (spine, -1.06 +/- 0.86; forearm, -1.04 +/- 0.86) was significantly lower than that for patients with ulcerative colitis (spine, -0.03 +/- 1.16; forearm, 0.11 +/- 1.24). Inflammatory activity, disease localization, body mass index, smoking habits, sex, physical activity, or biochemical parameters did not account for this difference. Spine and forearm Z scores were significantly correlated. Mean Z scores after 1 year were not significantly different from initial Z scores.

At diagnosis, low bone mineralization is a feature of Crohn's disease but not ulcerative colitis. Treatment with corticosteroids did not result in further bone loss in 1 year.