Genetics and bone mineral density predict the fractures in adults with osteogenesis imperfecta: a prospective study.

Context: Osteogenesis imperfecta (OI) is a rare genetic bone disorder characterized by recurrent fractures. In adults, the value of bone mineral density (BMD) in fracture risk is unknown.

Objective: We prospectively investigated changes in BMD over time and analysed the determinants of fracture in OI.

Methods: Among 106 individuals with grade 1 and 4 OI in the Reference Centre of Rare Bone Diseases in Paris, we included those with BMD measurements at one or more skeletal sites (hip, lumbar spine, radius) from 2000 to 2022.

Results: For 71 individuals with reliable measurements (44 women, 8 postmenopausal; mean age 41.4 ± 13.7 years), baseline BMD was low at the lumbar spine only (mean Z-score -2.3±1.5), affecting mainly men (mean Z-score -3±1.6). Longitudinal changes were assessed for a median follow-up of 5.1 years (interquartile range 3.2-8.8). On adjustment for age, sex and body mass index, BMD did not significantly change at any site. Logistic regression analysis revealed a high probability of fracture with baseline BMD Z-score <-2 SD versus ≥-2 SD (odds ratio 4.38, 95% CI 1.10-21.75, p=0.048) and harbouring splicing, stop codon and frameshift variants of COL1 gene (odds ratio 29.8, 95% CI 2.56-1503, p=0.024).

Conclusion: our OI cohort showed low BMD at the lumbar spine but no significant change at any site after a median of 5.0 years of follow-up. The probability of fracture was associated with baseline BMD Z-score <-2 SD versus ≥-2 SD and harbouring COL1 splicing, stop codon and frameshift variants.