Bone density in osteogenesis imperfecta may well be normal

Abstract

Summary:Osteogenesis imperfecta (01) is often regarded as a form of osteoporosis. However, the bone fragility is the result of defective collagen and earlier work has demonstrated that cortical thickness, in bones not previously fractured, is usually normal. We have now measured the bone mineral content of the distal forearm in 61 adult patients with well characterized OI.Three patients with the Sillence type III disorder had bone mass values well below the reference interval. For the 47 type I patients and 11 type IV patients, the bone mass was significantly lower than normal (P < 0.001). However 70% of patients had values within the reference interval. One cannot therefore exclude the diagnosis of 01 by finding normal values with densitometry.Diagnostic difficulties do not occur in type HI patients and our main objective was to recruit as many individuals as possible with OI types I and IV. In the type IV disease, the diagnosis can be particularly difficult without a positive family history. Since the evaluation of bone density by subjective examination of radiographs is a much less precise procedure, most patients with type I and IV 01 would be expected to have 'normal' appearances with this assessment. Osteogenesis imperfecta cannot be excluded on the basis of apparently normal bone density or cortical thickness with routine radiographs.

Type I Collagen Racemization and Isomerization and the Risk of Fracture in Postmenopausal Women: The OFELY Prospective Study

“…(22)(23)(24) Although most OI patients have subnormal BMD, some have decreased bone strength but normal BMD, (25) providing evidence that type I collagen structure may be related to changes in mechanical strength independently of BMD.…”

Genetics of Osteoporosis

“…Some studies have identified structurally relevant mutations in the collagen 1␣1 gene in familial forms of osteoporosis as distinct from osteogenesis imperfecta (122)(123)(124)(125)(126). In one of these studies almost one in five subjects of a selected group had such mutations (123).…”

Bone Density Measurements by Computed Tomography in Osteogenesis Imperfecta Type I

“…Since adults with OI-type I have a low TBD and high CBD, methods of bone density measurement that cannot distinguish CBD from TBD might give normal results with this type of bone density profile, such as the results of the Paterson study [4]. Absorptiometric bone measurement determines an areal bone density that is influenced by bone size.…”

“…Davie and Haddaway [3], who used dual-photon absorptiometry of the lumbar spine and femoral neck to study 9 children with OI-type I ages 6-12 years, found that the children with OI-type I tended to have lower bone density, but that there was overlap with the normal children. Paterson and Mole [4] used singlephoton absorptiometry of the forearm to study individuals over age 20 years with OI-type I and found that most OI-type I individuals had normal bone density. Zionts et al [5] also used dual-photon absorptiometry of the lumbar spine and femoral neck to study 9 children with OI-type I ages 2-13 years and compared their bone density values with age-and sex-matched controls.…”

“…In either situation the osteoid that is formed is unable to maintain normal mineralization, and this is the basis of the increased bone weakness and fracture susceptibility. Studies measuring bone density in individuals with OI-type I using the techniques of single-and dual-energy absorptiometry have given equivocal results as to whether there is decreased bone density in OI-type I individuals [3][4][5].…”