Bone mineral content and collagen defects in osteogenesis imperfecta

Whole-body and spine dual-energy X-ray absorptiometry was done in 63 patien ts with osteogenesis imperfecta aged 5 to 63 y, and the results were compar ed with OI types and collagen defects. Bone mineral content (BMC)-for-age, bone area (BA)-for-age, bone mineral density (BMD)for-age, and BMC-for-BA w ere reduced, especially in patients with OI III/IV and/or in those with a q ualitative collagen defect. BA-for-height was normal. Some patients with OI I and/or a quantitative collagen defect had BMD at or above -2 z-scores. W e conclude (i) that both BMC and BMD differ significantly between OI types and collagen defects, (ii) that reduced BMC-forage in OI patients is due ma inly to reduced height ("short bones") and reduced BMC-for-BA ("light bones "), whereas BA-for-height ("bone width") is normal, (iii) that most OI pati ents have lower than average BMC, but in some mildly affected patients brit tleness may exist with only small reductions in BMC.