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Eastern Regional Meeting - 2008 Program & Abstracts
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POPCORN CALCIFICATION IN OSTEOGENESIS IMPERFECTA
A.A. Obafemi, J.C. Marini, Bone and Extracellular Matrix Branch, NICHD/NIH, Bethesda, MD; A.A. Obafemi, UMDNJ-New Jersey Medical School, Newark, NJ
Purpose of Study: To determine whether there is an association between the incidence of popcorn calcification and OI types, particularly types III and IV.
Methods Used: Serial lower limb radiographs of 45 OI patients with Sillence types III & IV and known collagen mutations were retrospectively analyzed for popcorn calcification. These patients were also analyzed according to the a chain in which their mutation occurs.
Summary of Results: Popcorn calcifications were identified in the radiographs of 13 of 25 (52%) Type III OI children, while only 2 of 20 (10%) children with Type IV OI had popcorn calcifications. The two positive type IV children both have a more severe phenotype. The mean age of onset was 7years (range 4-14 years). Popcorn calcifications were found predominantly in the distal femora, although some patients also had popcorn in proximal tibiae. Popcorn onset in the femurs was simultaneous in 7 of 10 cases (70%); when popcorn in one femur preceded the other, the interval was generally 1 year, except for one patient in whom it was 4years. Popcorn onset in distal femurs always preceded tibial onset and there were no cases in which popcorn occurred only in the tibiae. In type III OI, we found no preference for popcorn calcifications by the chain in which the mutation was located. They occurred in 53% of patients with a1(1) and 50% of patients with a2(1) mutations. The two positive type IV children both have a1(1) mutations. Mutations associated with popcorn calcifications are distributed evenly along the collagen chains. It is noteworthy that popcorn calcifications have also been described in two children with non-lethal form of type VIII OI. These patients exhibited popcorn calcifications in radiographs of both upper and lower extremities.
Conclusions: Popcorn calcifications, representing disruption of the growth plate, occur in severe cases of OI with both collagen structural defects (predominantly type III OI) and collagen modification defects (type VIII OI) and cannot be used to distinguish dominant and recessive OI forms.
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