Cesarean delivery is not associated with decreased at-birth fracture rates in osteogenesis imperfecta.

PURPOSE: Osteogenesis imperfecta (OI) predisposes to recurrent fractures. Patients with the moderate to severe forms of OI present with antenatal fractures, and the mode of delivery that would be safest for the fetus is not known. METHODS: We conducted systematic analyses of the largest cohort of individuals with OI (n = 540) enrolled to date in the OI Linked Clinical Research Centers. Self-reported at-birth fracture rates were compared among individuals with OI types I, III, and IV. Multivariate analyses utilizing backward-elimination logistic regression model building were performed to assess the effect of multiple covariates, including method of delivery, on fracture-related outcomes. RESULTS: When accounting for other covariates, at-birth fracture rates did not differ based on whether delivery was by vaginal route or by cesarean delivery (CD). Increased birth weight conferred higher risk for fractures irrespective of the delivery method. In utero fracture, maternal history of OI, and breech presentation were strong predictors for choosing CD. CONCLUSION: Our study, the largest to analyze the effect of various factors on at-birth fracture rates in OI, shows that CD is not associated with decreased fracture rate. With the limitation that the fracture data were self-reported in this cohort, these results suggest that CD should be performed only for other maternal or fetal indications, not for the sole purpose of fracture prevention in OI.Genet Med 18 6, 570-576.

A cross-sectional multicenter study of osteogenesis imperfecta in North America - results from the linked clinical research centers.

Osteogenesis imperfecta (OI) is the most common skeletal dysplasia that predisposes to recurrent fractures and bone deformities. In spite of significant advances in understanding the genetic basis of OI, there have been no large-scale natural history studies. To better understand the natural history and improve the care of patients, a network of Linked Clinical Research Centers (LCRC) was established. Subjects with OI were enrolled in a longitudinal study, and in this report, we present cross-sectional data on the largest cohort of OI subjects (n = 544). OI type III subjects had higher prevalence of dentinogenesis imperfecta, severe scoliosis, and long bone deformities as compared to those with OI types I and IV. Whereas the mean lumbar spine area bone mineral density (LS aBMD) was low across all OI subtypes, those with more severe forms had lower bone mass. Molecular testing may help predict the subtype in type I collagen-related OI. Analysis of such well-collected and unbiased data in OI can not only help answering questions that are relevant to patient care but also foster hypothesis-driven research, especially in the context of 'phenotypic expansion' driven by next-generation sequencing.

Successful endovascular repair of acute type B aortic dissection in undiagnosed Ehlers-Danlos syndrome type IV.

A 61-year-old man presented with an acute type B aortic dissection for which a stent-graft was introduced. He remains complication-free 4 years onwards and has since been diagnosed with Ehlers-Danlos syndrome type IV (EDS IV). His particular mutation is predicted to result in lesser levels of normal collagen and may explain his favourable outcome from endovascular intervention. Understanding the genotype-phenotype correlation may influence the choice of therapy offered to patients with EDS IV.

Analysis of multigenerational families with thoracic aortic aneurysms and dissections due to TGFBR1 or TGFBR2 mutations.

BACKGROUND: Mutations in the transforming growth factor beta receptor type I and II genes (TGFBR1 and TGFBR2) cause Loeys-Dietz syndrome (LDS), characterised by thoracic aortic aneurysms and dissections (TAAD), aneurysms and dissections of other arteries, craniosynostosis, cleft palate/bifid uvula, hypertelorism, congenital heart defects, arterial tortuosity, and mental retardation. TGFBR2 mutations can also cause TAAD in the absence of features of LDS in large multigenerational families, yet only sporadic LDS cases or parent-child pairs with TGFBR1 mutations have been reported to date. METHODS: The authors identified TGFBR1 missense mutations in multigenerational families with TAAD by DNA sequencing. Clinical features of affected individuals were assessed and compared with clinical features of previously described TGFBR2 families. RESULTS: Statistical analyses of the clinical features of the TGFBR1 cohort (n = 30) were compared with clinical features of TGFBR2 cohort (n = 77). Significant differences were identified in clinical presentation and survival based on gender in TGFBR1 families but not in TGFBR2 families. In families with TGFBR1 mutations, men died younger than women based on Kaplan-Meier survival curves. In addition, men presented with TAAD and women often presented with dissections and aneurysms of arteries other than the ascending thoracic aorta. The data also suggest that individuals with TGFBR2 mutations are more likely to dissect at aortic diameters <5.0 cm than individuals with TGFBR1 mutations. CONCLUSION: This study is the first to demonstrate clinical differences between patients with TGFBR1 and TGFBR2 mutations. These differences are important for the clinical management and outcome of vascular diseases in these patients.

The bicuspid aortic valve: an integrated phenotypic classification of leaflet morphology and aortic root shape.

OBJECTIVE: To establish a classification of bicuspid aortic valve (BAV) that includes both leaflet morphology and aortic shape. SETTING: Two academic medical centres of the University of Washington, Seattle. PATIENTS: 191 adult patients with BAV. INTERVENTIONS: Review of clinical data and transthoracic echocardiograms. MAIN OUTCOME MEASURES: Assessment of leaflet morphology; valve function; aortic shape and dimensions. RESULTS: We identified three morphologies: type 1, fusion of right and left coronary cusp (n = 152); type 2, right and non-coronary fusion (n = 39); and type 3, left and non-coronary fusion (n = 1). Comparing type 1 and 2 BAV, there were no significant differences in age, height, weight, blood pressure or aortic valve function. Type 1 was more common in men (69 vs 45%). The aortic sinuses were larger in type 1, while type 2 had larger arch dimensions. Myxomatous mitral valves were more common in type 2 BAV (13% vs 2.6%, p<0.05). Three aortic shapes were defined: normal (N), sinus effacement (E), and ascending dilatation (A). Comparing type 1 to type 2 BAV, shape N was more common in type 1 (60% vs 32%), and type A was more common in type 2 (35% vs 54%,); type E was rare (p<0.01 across all groups). CONCLUSION: A comprehensive BAV phenotype includes aortic shape. Type 1 BAV is associated with male gender and normal aortic shape but a larger sinus diameter. Type 2 leaflet morphology is associated with ascending aorta dilatation , larger arch dimensions and higher prevalence of myxomatous mitral valve disease.

Neurological presentation of Ehlers-Danlos syndrome type IV in a family with parental mosaicism.

Ehlers-Danlos syndrome type IV (EDS-IV) is an autosomal-dominant disorder caused by a defect of type III collagen which leads to ruptures of arteries and hollow organs. Neurological presentation with muscle involvement and flexion contractures of the finger joints is uncommon. We clinically characterized seven members of a family with EDS-IV. The index patient, a young woman with an acrogeric face, suffered chronic muscle pain and cramps, Achilles tendon retraction, finger flexion contractures and seizures. The mother had similar features and had experienced an ischemic stroke. Biochemical study in cultured fibroblasts and molecular analysis of the COL3A1 gene led to the diagnosis of EDS-IV. A glycine substitution, p.G883V, within the triple helix of the alpha 1(III) chain, was found in the index patient and in the mother. The maternal grandfather and an aunt each had an abdominal aortic aneurysm, the rupture of which was the cause of death in the latter, at 40 years of age. Surprisingly, we found the mutation, as a mosaic, in the asymptomatic maternal grandmother. This expands the clinical spectrum of EDS type IV and confirms that in some families mosaicism can be identified as the source of the mutation.

Testing for osteogenesis imperfecta in cases of suspected non-accidental injury.

To evaluate if laboratory testing for osteogenesis imperfecta (OI) identifies children unrecognised by clinical examination in instances where non-accidental injury (NAI) is suspected as the likely cause of fracture, we carried out a retrospective review of available medical records and biochemical test results from 262 patients. Cultured fibroblasts were received for biochemical testing for OI from children in whom the diagnosis of NAI was suspected. Eleven of the samples had alterations in the amount or structure of type I collagen synthesised, consistent with the diagnosis of OI, and in 11 others we could not exclude OI. Referring physicians correctly identified children with OI in six of the 11 instances established by biochemical studies, did not identify OI by clinical examination in three, and there was inadequate clinical information to know in two others. Biochemical testing was inconclusive in 11 infants in whom the diagnosis of OI could not be excluded, none of whom were thought to be affected by the referring clinicians. Four children believed to have OI by clinical examination had normal biochemical studies, a false positive clinical diagnosis attributed, in large part, to the use of scleral hue (a feature that is age dependent) as a major diagnostic criterion. Given the inability to identify all children with OI by clinical examination in situations of suspected NAI, laboratory testing for OI (and other genetic predispositions for fractures) is a valuable adjunct in discerning the basis for fractures and may identify a small group of children with previously undiagnosed OI.

A single amino acid substitution (D1441Y) in the carboxyl-terminal propeptide of the proalpha1(I) chain of type I collagen results in a lethal variant of osteogenesis imperfecta with features of dense bone diseases.

Osteogenesis imperfecta (OI) is characterised by brittle bones and caused by mutations in the type I collagen genes, COL1A1 and COL1A2. We identified a mutation in the carboxyl-terminal propeptide coding region of one COL1A1 allele in an infant who died with an OI phenotype that differed from the usual lethal form and had regions of increased bone density. The newborn female had dysmorphic facial features, including loss of mandibular angle. Bilateral upper and lower limb contractures were present with multiple fractures in the long bones and ribs. The long bones were not compressed and their ends were radiographically dense. She died after a few hours and histopathological studies identified extramedullary haematopoiesis in the liver, little lamellar bone formation, decreased osteoclasts, abnormally thickened bony trabeculae with retained cartilage in long bones, and diminished marrow spaces similar to those seen in dense bone diseases such as osteopetrosis and pycnodysostosis. The child was heterozygous for a COL1A1 4321G-->T transversion in exon 52 that changed a conserved aspartic acid to tyrosine (D1441Y). Abnormal proalpha1(I) chains were slow to assemble into dimers and trimers, and abnormal molecules were retained intracellularly for an extended period. The secreted type I procollagen molecules synthesised by cultured dermal fibroblasts were overmodified along the full length but had normal thermal stability. These findings suggest that the unusual phenotype reflected both a diminished amount of secreted type I procollagen and the presence of a population of stable and overmodified molecules that might support increased mineralisation or interfere with degradation of bone.

Deletions and duplications of Gly-Xaa-Yaa triplet repeats in the triple helical domains of type I collagen chains disrupt helix formation and result in several types of osteogenesis imperfecta.

Triple helix formation is a prerequisite for the passage of type I procollagen from the endoplasmic reticulum and secretion from the cell to form extracellular fibrils that will support mineral deposition in bone. Analysis of cDNA from 11 unrelated individuals with osteogenesis imperfecta (OI) revealed the presence of 11 novel, short in-frame deletions or duplications of three, nine, or 18 nucleotides in the helical coding regions of the COL1A1 and COL1A2 collagen genes. Triple helix formation was impaired, type I collagen alpha chains were post-translationally overmodified, and extracellular secretion was markedly reduced. With one exception, the obligate Gly-Xaa-Yaa repeat pattern of amino acids in the helical domains was not altered, but the Xaa- and Yaa position residues were out of register relative to the amino acid sequences of adjacent chains in the triple helix. Thus, the identity of these amino acids, in addition to third position glycines, is important for normal helix formation. These findings expand the known repertoire of uncommon in-frame deletions and duplications in OI, and provide insight into normal collagen biosynthesis and collagen triple helix formation.

Haploinsufficiency for one COL3A1 allele of type III procollagen results in a phenotype similar to the vascular form of Ehlers-Danlos syndrome, Ehlers-Danlos syndrome type IV.

Mutations in the COL3A1 gene that encodes the chains of type III procollagen result in the vascular form of Ehlers-Danlos syndrome (EDS), EDS type IV, if they alter the sequence in the triple-helical domain. Although other fibrillar collagen-gene mutations that lead to allele instability or failure to incorporate proalpha-chains into trimers-and that thus reduce the amount of mature molecules produced-result in clinically apparent phenotypes, no such mutations have been identified in COL3A1. Furthermore, mice heterozygous for Col3a1 "null" alleles have no identified phenotype. We have now found three frameshift mutations (1832delAA, 413delC, and 555delT) that lead to premature termination codons (PTCs) in exons 27, 6, and 9, respectively, and to allele-product instability. The mRNA from each mutant allele was transcribed efficiently but rapidly degraded, presumably by the mechanisms of nonsense-mediated decay. In a fourth patient, we identified a point mutation, in the final exon, that resulted in a PTC (4294C-->T [Arg1432Ter]). In this last instance, the mRNA was stable but led to synthesis of a truncated protein that was not incorporated into mature type III procollagen molecules. In all probands, the presenting feature was vascular aneurysm or rupture. Thus, in contrast to mutations in genes that encode the dominant protein of a tissue (e.g., COL1A1 and COL2A1), in which "null" mutations result in phenotypes milder than those caused by mutations that alter protein sequence, the phenotypes produced by these mutations in COL3A1 overlap with those of the vascular form of EDS. This suggests that the major effect of many of these dominant mutations in the "minor" collagen genes may be expressed through protein deficiency rather than through incorporation of structurally altered molecules into fibrils.

Disruption of one intra-chain disulphide bond in the carboxyl-terminal propeptide of the proalpha1(I) chain of type I procollagen permits slow assembly and secretion of overmodified, but stable procollagen trimers and results in mild osteogenesis imperfecta.

Type I procollagen is a heterotrimer comprised of two proalpha1(I) chains and one proalpha2(I) chain. Chain recognition, association, and alignment of proalpha chains into correct registration are thought to occur through interactions between the C-terminal propeptide domains of the three chains. The C-propeptide of each chain contains a series of cysteine residues (eight in proalpha1(I) and seven in proalpha2(I)), the last four of which form intra-chain disulphide bonds. The remaining cysteine residues participate in inter-chain stabilisation. Because these residues are conserved, they are thought to be important for folding and assembly of procollagen. We identified a mutation (3897C-->G) that substituted tryptophan for the cysteine at position 1299 in proalpha1(I) (C1299W, the first cysteine that participates in intra-chain bonds) and resulted in mild osteogenesis imperfecta. The patient was born with a fractured clavicle and four rib fractures. By 18 months of age he had had no other fractures and was on the 50th centile for length and weight. The proband's mother, maternal aunt, and grandfather had the same mutation and had few fractures, white sclerae, and discoloured teeth, but their heights were within the normal range. In the patient's cells the defective chains remained as monomers for over 80 minutes (about four times normal) and were overmodified. Some secreted procollagens were also overmodified but had normal thermal stability, consistent with delayed, but normal helix formation. This intra-chain bond may stabilise the C-propeptide and promote rapid chain association. Other regions of the C-propeptide thus play more prominent roles in chain registration and triple helix nucleation.

Folding defects in fibrillar collagens.

Fibrillar collagens have a long triple helix in which glycine is in every third position for more than 1000 amino acids. The three chains of these molecules are assembled with specificity into several different molecules that have tissue-specific distribution. Mutations that alter folding of either the carboxy-terminal globular peptides that direct chain association, or of the regions of the triple helix that are important for nucleation, or of the bulk of the triple helix, all result in identifiable genetic disorders in which the phenotype reflects the region of expression of the genes and their tissue-specific distribution. Mutations that result in changed amino-acid sequences in any of these regions have different effects on folding and may have different phenotypic outcomes. Substitution for glycine residues in the triple helical domains are among the most common effects of mutations, and the nature of the substituting residue and its location in the chain contribute to the effect on folding and also on the phenotype. More complex mutations, such as deletions or insertions of triple helix, also affect folding, probably because of alterations in helical pitch along the triple helix. These mutations all interfere with the ability of these molecules to form the characteristic fibrillar array in the extracellular matrix and many result in intracellular retention of abnormal molecules.

Osteogenesis imperfecta: mode of delivery and neonatal outcome.

OBJECTIVE: To evaluate the pregnancy characteristics, methods of delivery, and neonatal outcomes of fetuses affected by osteogenesis imperfecta. METHODS: We reviewed medical records of 1016 individuals whose cells were sent to the University of Washington Collagen Diagnostic Laboratory between 1987 and 1994 for confirmation of diagnoses of osteogenesis imperfecta. Information and neonatal records were available for 167 of those pregnancies. From those we identified method(s) of prenatal detection, delivery method, and neonatal complications, including survival and acquisition of new fractures, and related them to type of delivery. RESULTS: The cesarean delivery rate was 54%, most of them (53%) for nonvertex presentation and fewer than 15% because of an antenatal diagnoses of osteogenesis imperfecta. There was an unusually high rate of breech presentation at term (37%). In infants with nonlethal forms of osteogenesis imperfecta, 24 of 59 (40%) delivered by cesarean and 17 of 53 (32%) delivered vaginally had new fractures (chi(2) =.89; P =.3). Among 55 infants with the most severe form, 24 of 31 delivered by cesarean and 21 of 24 delivered vaginally died within 2 weeks of birth. CONCLUSION: Cesarean delivery did not decrease fracture rates at birth in infants with nonlethal forms of osteogenesis imperfecta nor did it prolong survival for those with lethal forms. Prenatal diagnosis did not influence mode of delivery in most instances. Most cesarean deliveries were done for usual obstetric indications.

Osteogenesis imperfecta: perspectives and opportunities.

The last 2 years have seen additions proposed to the very limited armamentarium of treatments for osteogenesis imperfecta. These include the use of bisphosphonates to decrease bone resorption, growth hormone to augment growth and collagen production, and bone marrow transplantation to create chimeras at the level of the collagen production unit in bone. Although there are optimistic proponents for each strategy, the lack of well-controlled studies and the absence of clearly defined objectives for therapy hinder clear assessment.

Pressure ulcer research issues in surgical patients.

This paper focuses on key pressure ulcer research issues in surgical patients pertaining to incidence, risk assessment, temporality, methodology, and interpretation and utilization of findings. The recent emphasis on the effect of intraoperative events on pressure ulcer occurrence is discussed in terms of the underlying conceptualization, theoretical and empirical evidence, and consequences for research. The ongoing quest for predictors of pressure ulcers in surgical patients and the results of clinical studies in this population illustrate the limitations of current pressure ulcer risk assessment instruments; therefore, an example of an alternative risk assessment strategy for surgical patients is presented. Addressing these issues in a timely fashion is important given their potential impact on future research and the growing interest in studying pressure ulcers in surgical patients.

Collagens: building blocks at the end of the development line.

Collagens are some of the major building blocks of the vertebrate body. In addition to their structural role, they are important for cell guidance during development and for maintaining tissue integrity. In their absence, phenotypes range from lethal to mild. These studies demonstrate that collagens,in their rich array, play important roles in development and are significant elements in reading the developmental code.

Partial COL1A2 gene duplication produces features of osteogenesis imperfecta and Ehlers-Danlos syndrome type VII.

Type I collagen is the most abundant structural protein in the mammalian body. It exists as a heterotrimer of two subunits in the form [alpha1(I)]2alpha2(I). Pathogenic mutations in COL1A1 and COL1A2, the genes that encode the two subunits, cause a range of phenotypes including mild to lethal forms of osteogenesis imperfecta and a restricted set of Ehlers-Danlos syndrome phenotypes. Lethal mutations usually result from missense mutations that disrupt the normal triple helical structure of the molecule. Multi-exon duplication or deletion in type I collagen genes has rarely been observed and has generally resulted in a lethal or severe phenotype. We report a partial duplication in the COLIA2 gene that causes a relatively mild phenotype, despite the addition of 477 amino acids to the triple helical domain of the proalpha2(I) chain. The abnormal molecule is synthesized and secreted by cultured dermal fibroblasts in a normal fashion. Electron microscopy of dermal tissue reveals small but otherwise near normal collagen fibrils. The gene duplication occurred by mitotic sister chromatid exchange in the mother who is mosaic for the duplication allele. Examination of the abnormal sequence suggests a means by which the duplicated molecule could be processed and properly incorporated into mature collagen fibrils.

Null alleles of the COL5A1 gene of type V collagen are a cause of the classical forms of Ehlers-Danlos syndrome (types I and II).

Ehlers-Danlos syndrome (EDS) types I and II, which comprise the classical variety, are well characterized from the clinical perspective, but it has been difficult to identify the molecular basis of the disorder in the majority of affected individuals. Several explanations for this failure to detect mutations have been proposed, including genetic heterogeneity, failure of allele expression, and technical difficulties. Genetic heterogeneity has been confirmed as an explanation for such failure, since causative mutations have been identified in the COL5A1, COL5A2, and tenascin X genes and since they have been inferred in the COL1A2 gene. Nonetheless, in the majority of families with autosomal dominant inheritance of EDS, there appears to be linkage to loci that contain the COL5A1 or COL5A2 genes. To determine whether allele-product instability could explain failure to identify some mutations, we analyzed polymorphic variants in the COL5A1 gene in 16 individuals, and we examined mRNA for the expression of both alleles and for alterations in splicing. We found a splice-site mutation in a single individual, and we determined that, in six individuals, the mRNA from one COL5A1 allele either was not expressed or was very unstable. We identified small insertions or deletions in five of these cell strains, but we could not identify the mutation in the sixth individual. Thus, although as many as one-half of the mutations that give rise to EDS types I and II are likely to lie in the COL5A1 gene, a significant portion of them result in very low levels of mRNA from the mutant allele, as a consequence of nonsense-mediated mRNA decay.