Obafemi Abimbola A, Bulas Dorothy I, Troendle James, Marini Joan C
Bone and Extracellular Matrix Branch, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892, USA.
Am J Med Genet A. 2008 Nov 1;146A(21):2725-32. doi: 10.1002/ajmg.a.32508.
Osteogenesis imperfecta (OI) is a heritable disorder characterized by osteoporosis and increased susceptibility to fracture. All children with severe OI have extreme short stature and some have "popcorn" calcifications, areas of disorganized hyperdense lines in the metaphysis and epiphysis around the growth plate on lower limb radiographs. Popcorn calcifications were noted on radiographs of two children with non-lethal type VIII OI, a recessive form caused by P3H1 deficiency. To determine the incidence, progression, and molecular correlations of popcorn calcifications, we retrospectively examined serial lower limb radiographs of 45 children with type III or IV OI and known dominant mutations in type I collagen. Popcorn calcifications were present in 13 of 25 type III (52%), but only 2 of 20 type IV (10%), OI children. The mean age of onset was 7.0 years, with a range of 4-14 years. All children with popcorn calcifications had this finding in their distal femora, and most also had calcifications in proximal tibiae. While unilateral popcorn calcification contributes to femoral growth deficiency and leg length discrepancy, severe linear growth deficiency, and metaphyseal flare do not differ significantly between type III OI patients with and without popcorn calcifications. The type I collagen mutations associated with popcorn calcifications occur equally in both COL1A1 and COL1A2, and have no preferential location along the chains. These data demonstrate that popcorn calcifications are a frequent feature of severe OI, but do not distinguish cases with defects in collagen structure (primarily dominant type III OI) or modification (recessive type VIII OI).
成骨不全症（OI）是一种遗传性疾病，其特征为骨质疏松和骨折易感性增加。所有患有严重OI的儿童身材极度矮小，部分儿童有“爆米花”样钙化，即下肢X线片显示生长板周围干骺端和骨骺处出现紊乱的高密度线区域。在两名患有非致死性VIII型OI（由P3H1缺乏引起的隐性形式）的儿童X线片上发现了“爆米花”样钙化。为了确定“爆米花”样钙化的发生率、进展情况及其分子相关性，我们回顾性检查了45例患有III型或IV型OI且已知I型胶原显性突变的儿童的系列下肢X线片。25例III型OI儿童中有13例（52%）出现“爆米花”样钙化，而20例IV型OI儿童中仅有2例（10%）出现。平均发病年龄为7.0岁，范围为4至14岁。所有出现“爆米花”样钙化的儿童在股骨远端均有此表现，大多数儿童在胫骨近端也有钙化。虽然单侧“爆米花”样钙化会导致股骨生长不足和腿长差异，但严重的线性生长不足和干骺端增宽在有和没有“爆米花”样钙化的III型OI患者之间并无显著差异。与“爆米花”样钙化相关的I型胶原突变在COL1A1和COL1A2中出现的频率相同，且在链上没有优先位置。这些数据表明，“爆米花”样钙化是严重OI的常见特征，但无法区分胶原结构缺陷（主要是显性III型OI）或修饰缺陷（隐性VIII型OI）的病例。
