Abstract

The features of three babies with lethal perinatal osteogenesis imperfecta resulting from the substitution of glycine by arginine in the pro alpha 1(I) chain of type I procollagen were studied. The babies were heterozygous for this substitution at residue 391 in case 1 (0I24), 667 in case 2 (0I51), and 976 in case 3 (0I30). They were all small, term babies who died soon after birth. The ribs were broad and continuously beaded in 0I24, discontinuously beaded in 0I51, and slender with few fractures in 0I30. The overall radiographical classifications were type IIA in 0I24, IIA/IIB in 0I51, and IIB in 0I30. Histological examination confirmed that the long bones were misshapen and porotic. The calcified cartilage trabeculae were covered with an abnormally thin layer of osteoid and the bone trabeculae were thin and basophilic. There was no evidence of lamellar bone or Haversian systems. The osteoblasts remained relatively large and closely spaced. These babies shared many phenotypic features, but differences in the radiographical appearance of the ribs and long bones suggested that there was a gradient of bone modelling capacity from the slender and overmodelled bones in 0I30 to the absence of modelling in 0I24.