Bone density measurements by computed tomography in osteogenesis imperfecta type I

The objectives of this study were (1) to determine whether there are differ ences in bone density in children versus adults with osteogenesis imperfect a type I(OI-type I) using computed tomography (CT) bone density measurement s, (2) to determine whether there are differences in bone density between n ormal infants and infants with OI-type I using CT bone density measurements and (3) to determine whether CT bone density measurements could be helpful in investigating the infant with unexplained fractures. CT bone density me asurements determine both the cortical bone density (CBD) and the trabecula r bone density (TBD). CT bone density was determined using the OsteoQuant i n 14 individuals with OI-type I who ranged in ages from 8 months to 45 year s. The control groups consisted of over 1000 normal individuals, mostly adu lts, and included 7 normal infants who ranged in age from 10 months to 27 m onths. One of the individuals with OI-type I was a 4-month-old infant with multiple, unexplained fractures who had no other features of OI-type I and whose parents were accused of child abuse. Infants and children with OI-typ e I had low CBD and low TBD compared with normal controls, whereas adults w ith OI-type I had low TBD and high CBD when compared with controls. The one infant with multiple unexplained fractures and no other features of OI-typ e I had a bone density profile suggesting OI-type I with a low TBD and low CBD. Subsequent collagen analysis showed biochemical evidence of OI-type I. Individuals with OI-type I have abnormal CT bone density profiles that evo lve over time from a low CBD and low TBD during infancy and childhood to a high CBD and low TBD during adulthood. This may explain the decreased frequ ency of fractures in individuals with OI-type I in adulthood compared with childhood. Individuals with OI-type I can present with only multiple unexpl ained fractures and have no other clinical features to strongly suggest the diagnosis. CT bone density measurements can be helpful in these atypical c ases of OI-type I and should be considered in the investigation of the infa nt with unexplained fractures to help distinguish intrinsic bone disease fr om child abuse.