Endocrine Abstracts

Introduction: Osteogenesis imperfecta (OI) is a rare genetic disorder characterised by reduced bone mineral density (BMD) and increased susceptibility to fractures. In the general population, higher BMI is positively associated with BMD and may lower fracture risk, but this relationship remains underexplored in children with OI. This study investigated associations between standardised BMI (BMI SDS), the number of vertebral fractures, and BMD in a paediatric OI cohort.

Methods: Data were analysed from children with OI managed at a tertiary UK centre. Data included BMI, vertebral fracture count from dual-energy X-ray absorptiometry (DXA) or spinal radiographs, and DXA-derived BMD measures prior to bisphosphonate therapy. BMI SDS was calculated using UK population reference data. Overweight and obesity were classified as BMI SDS of ≥1.33 and ≥2 respectively. Statistical analyses assessed associations between BMI SDS, vertebral fractures, and bone density measures.

Results: Eighty-six patients (56.5% female, mean age 10.6 years) with confirmed OI were included in the data analysis. Mean BMI SDS was higher than the general population (0.427; 95% CI 0.230–0.624, P = 0.001), with 25.6% in the overweight/obesity categories. Fifty-seven percent had at least one vertebral fracture. There was no association between mean BMI SDS and number of vertebral fractures (rho = 0.096, P = 0.378). There was no association between having a BMI in the overweight/obesity range and the presence of at least one vertebral fracture (χ²=0.962, P = 0.326). BMI SDS showed no significant associations with most site-specific bone parameters, including lumbar spine bone mineral apparent density (BMAD) and pQCT measures. However, BMI SDS correlated positively with lean mass adjusted for height (rho = 0.483, P < 0.001), whole-body BMD and bone mineral content when adjusted for age and height respectively (rho = 0.606, P < 0.001; rho = 0.311, P < 0.05).

Conclusion: BMI SDS was higher in this paediatric OI cohort compared to the general population. BMI SDS does not appear to increase vertebral fracture risk in children with OI, but is positively associated with lean mass adjusted for height and whole-body less head BMD, possibly due to an impact on muscle mass and therefore bone health. The findings highlight the complex relationship between body composition, bone health and fracture risk in children with OI.