Strategy for prenatal diagnosis of osteogenesis imperfecta by linkage analysis to the type I collagen loci COL1A1 and COL1A2

To improve prenatal diagnosis of osteogenesis imperfecta (OI) in Lithuania, possibilities of indirect molecular genetic diagnosis were investigated in 11 families with dominant OI. Segregation of polymorphic DNA markers closely linked to COL1A1 and COL1A2 genes with OI phenotype was investigated. Polymorphic DNA markers applied were individual haplotypes constructed using a set of restriction enzyme sites within or close to the genes. Comparison of phenotypic features with the concordant collagen locus showed that in four pedigrees with OI Sillence type I segregated with COL1A1, while two pedigrees with OI Sillence type I and OI type IV segregated with COL1A2. Out of six remaining pedigrees with OI Sillence type I, three were concordant at both loci, two pedigrees were discordant at the locus COL1A2 and non-informative at the locus COL1A1 and one pedigree was concordant at the locus COL1A1 and non-informative at the locus COL1A2. Informativity of DNA markers applied was also investigated in the Lithuanian OI families. The frequencies of six restriction enzyme site dimorphisms in type I collagen loci were estimated and polymorphism information content (PIC) values were calculated for each restriction site and for a combination of three sites. COL1A1 locus dimorphisms A/MspI, B/RsaI and F/MnlI, showed PIC values of 0.327, 0.191 and 0.366, respectively, giving a combined PIC of 0.656 at the locus, while COL1A2 locus dimorphisms C/EcoRI, D/MspI and E/RsaI RFLPs had PIC values of 0.357, 0.168 and 0.331, respectively, giving a combined PIC of 0.655 at the locus.

The treatment of mandibular cysts associated with osteogenesis imperfecta

A fifteen-year-old boy with osteogenesis imperfecta (OI) and dentinogenesis imperfecta also had a big cyst in the mandible and needed surgical therapy. Six months postoperatively we saw a complete regeneration of the bone-structures. We came to the conclusion that cysts which appear independently from the disease of OI can heal after surgical intervention.

Two sibs with an unusual pattern of skeletal malformations resembling osteogenesis imperfecta: a new type of skeletal dysplasia?

We report a 6 year old boy with multiple fractures owing to bilateral, peculiar, wave-like defects of the tibial corticalis with alternative hyperostosis and thinning. Furthermore, he had Wormian bones of the skull, dentinogenesis imperfecta, and a distinct facial phenotype with hypertelorism and periorbital fullness. Collagen studies showed normal results. His sister, aged 2 years, showed the same facial phenotype and dental abnormalities as well as Wormian bones, but no radiographical abnormalities of the tubular bones so far. The mother also had dentine abnormalities but no skeletal abnormalities on x ray. This entity is probably the same as that described in a sporadic case by Suarez and Stickler in 1974. In spite of the considerable overlap with osteogenesis imperfecta (bone fragility, Wormian bones, and dentinogenesis imperfecta), we believe this disorder to be a different entity, in particular because of the unique cortical defects, missing osteopenia, and normal results of collagen studies.

Morphometric analysis of type I collagen fibrils in the osteoid of osteogenesis imperfecta

Electron microscopy and morphometric measurements of bone osteoid collagen diameter from 42 osteogenesis imperfecta (OI) patients and 25 age- and site-matched controls were carried out. Although the mean diameter did not correlate well with the severity of the disease, it related well with the clinical types and revealed collagen fibrils of reduced diameter in the osteoid of all OI types. Thus, OI type II (the severest type) demonstrated the smallest diameter (45 nm), followed by OI type I (the mildest form) with a mean diameter of 57 nm. The diameter obtained for type III (67 nm) and type IV (64 nm) was lower than the normal control mean diameter (73 nm) but did not show a statistical difference. The thinner fibrils observed in OI bone may be unable to provide nucleating and scaffolding sites for mineral propagation and may play a role in the fragility of bone in this disease.

Osteogenesis imperfecta in childhood: impairment and disability--a follow-up study

OBJECTIVES

To evaluate differences over time (mean follow-up, 14 months) on impairment parameters (range of joint motion and muscle strength), functional limitation parameters (functional ability), and disability parameters (caregiver assistance in achieving functional skills) in osteogenesis imperfecta (OI), related to the different types of the disease.

DESIGN

A prospective, descriptive study.

MATERIALS AND METHODS

Fifty-four children with OI and their parents participated at the start of the study. At the end, 44 children participated in the assessment of functional skills and 42 of them participated in clinical assessment (OI type I, n = 19; OI type III, n = 13; OI type IV, n = 10). Range of joint motion was measured by means of goniometry. Generalized hypermobility was scored according to Bulbena. Manual muscle strength was scored by means of the MRC grading system. The level of ambulation was scored according to Bleck, and functional skills and caregiver assistance were scored with the Pediatric Evaluation of Disability Inventory.

RESULTS

The different types of OI have impact on impairment, functional limitation, and disability. Almost all impairment parameters did not change significantly over time, whereas some disability parameters seemed to improve significantly.

CONCLUSIONS

Impairment parameters in OI are presumably not always preconditions for functional limitation and disability. A 1-year follow-up revealed no significant changes in impairment parameters, whereas some disability parameters improved. Treatment strategies in OI should, therefore, focus primarily on improving functional ability, with respect to the natural course of the disease, and not only on impairment parameters.

Extension of phenotype associated with structural mutations in type I collagen: siblings with juvenile osteoporosis have an alpha2(I)Gly436 --> Arg substitution

Mutations in the type I collagen genes have been identified as the cause of all four types of osteogenesis imperfecta (OI). We now report a mutation that extends the phenotype associated with structural abnormalities in type I collagen. Two siblings presented with a history of back pain and were diagnosed with juvenile osteoporosis, based on clinical and radiological examination. Radiographs showed decreased lumbar bone density and multiple compression fractures throughout the thoracic and lumbar spines of both patients. One child has moderate short stature and mild neurosensory hearing loss. However, neither child has incurred the long bone fractures characteristic of OI. Protein studies demonstrated electrophoretically abnormal type I collagen in samples from both children. Enzymatic cleavage of RNA:RNA hybrids identified a mismatch in type I collagen alpha2 (COL1A2) mRNA. DNA sequencing of COL1A2 cDNA subclones defined the mismatch as a single-base mutation (1715G --> A) in both children. This mutation predicts the substitution of arginine for glycine at position 436 (G436R) in the helical domain of the alpha2(I) chain. Analysis of genomic DNA identified the mutation in the asymptomatic father, who is presumably a germ-line mosaic carrier. The presence of the same heterozygous mutation in two siblings strongly suggests that the probands display the full phenotype. Taken together, the clinical, biochemical, and molecular findings of this study extend the phenotype associated with type I collagen mutations to cases with only spine manifestations and variable short stature into adolescence.

Joint hypermobility and genetic collagen disorders: are they related?

The HDCTs constitute a heterogeneous group of rare genetically determined diseases, the best known of which are Ehlers-Danlos and Marfan syndromes and osteogenesis imperfecta. Hypermobility is a feature common to them all, but it is also a feature that is highly prevalent in the population at large. Symptomatic hypermobile subjects (whose symptoms are attributable to their hypermobility) are said to be suffering from the benign joint hypermobility syndrome, which has many features that overlap with the HDCTs. It is not yet known whether there is a variety of hypermobility (symptomatic or otherwise) that is not part of a connective tissue disorder.

Osteogenesis imperfecta in childhood: treatment strategies

Osteogenesis imperfecta (OI) is a skeletal disorder of remarkable clinical variability characterized by bone fragility, osteopenia, variable degrees of short stature, and progressive skeletal deformities. Additional clinical manifestations such as blue sclerae, dentinogenesis imperfecta, joint laxity, and maturity onset deafness are described in the literature. OI occurs in about 1 in 20,000 births and is caused by quantitative and qualitative defects in the synthesis of collagen I. Depending on the severity of the disease, a large impact on motor development, range of joint motion, muscle strength, and functional ability may occur. Treatment strategies should primarily focus on the improvement of functional ability and the adoption of compensatory strategies, rather than merely improving range of joint motion and muscle strength. Surgical treatment of the extremities may be indicated to stabilize the long bones to optimize functional ability and walking capacity. Surgical treatment of the spine may be indicated in patients with progressive spinal deformity and in those with symptomatic basilar impression.

Recent findings in classification of osteogenesis imperfecta by means of existing dental symptoms

The findings are based on a clinical investigation conducted on forty-nine patients suffering from osteogenesis imperfecta (OI), as well as on a questionnaire study in which 117 osteogenesis imperfecta-affected persons or their parents were involved. The survey established pathological tooth discolorations as well as tooth abrasions. Dentinogenesis imperfecta (DI) was more frequently found in primary teeth than in permanent teeth. There were no gender-specific differences. Radiological abnormalities were found in both, abraded and/or discolored teeth, as well as in clinically normal appearing teeth. In most cases there were club-shaped extensions of the pulp chambers and obliterations of the root canals. The probability that dentinogenesis imperfecta occurs as an accompanying symptom of osteogenesis imperfecta was not dependent on the degree of skeletal severity. The self-assignment according to A and B forms of osteogenesis imperfecta types I and IV in accordance with the presence/absence of dental symptoms was contradictory, since the literature was based on varying classifications.

Osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetically determined disorder of connective tissue characterized by bone fragility. The disease state encompasses a phenotypically and genotypically heterogeneous group of inherited disorders that result from mutations in the genes that code for type I collagen. The disorder is manifest in tissues in which the principal matrix protein is type I collagen (mainly bone, dentin, sclerae, and ligaments). Musculoskeletal manifestations are variable in severity along a continuum ranging from perinatal lethal forms with crumpled bones to moderate forms with deformity and propensity to fracture to clinically silent forms with subtle osteopenia and no deformity. The differential diagnosis includes other entities with multiple fractures, deformities, and osteopenia. Classification is based on the timing of fractures or on multiple clinical, genetic, and radiologic features. Molecular genetic studies have identified more than 150 mutations of the COL1A1 and COL1A2 genes, which encode for type I procollagen. Various systemic treatments have been attempted; however, these interventions have been ineffective or inconclusive or are still experimental. Gene therapy has the potential to increase the synthesis of type I collagen in mild variants and to correct mutations in severe variants, but there are a great number of technical difficulties to overcome. The goals of treatment of OI are to maximize function, minimize deformity and disability, maintain comfort, achieve relative independence in activities of daily living, and enhance social integration. Attainment of these goals requires a team approach to tailor treatment needs to the severity of the disease and the age of the patient. Nonoperative management is the mainstay of orthopaedic treatment, with the goals of preventing and treating fractures and enhancing locomotion. Operative intervention is indicated for recurrent fractures or deformity that impairs function.

Osteogenesis imperfecta: a review

The wide spectra of the clinical features, classification, genetics and imaging features of osteogenesis imperfecta (OI) are discussed, especially in the context of distinguishing the condition from child abuse. A broad general knowledge of the clinical and genetic aspects of the disease, as well as the imaging features of OI, is required for radiologists to knowledgeably provide the proper diagnosis and to participate responsibly in a team approach with geneticists, clinicians, lawyers and child protection services. There are 4 major types of OI, ranging from mild to severe. The diagnosis is made from clinical, genetic and radiographic features. The complications of OI and the use of bone mineral density measurements, collagen analysis and prenatal ultrasonography are presented. Their clinical relevance to the diagnosis of OI are discussed. Skin biopsy for collagen analysis may be needed to aid in the diagnosis in confusing or mild cases. It is important to distinguish OI from child abuse in order to protect an abused child or to avoid an improper accusation of child abuse in a child with obvious OI.

Effects of withdrawal of bracing in matched pairs of children with osteogenesis imperfecta

OBJECTIVES

To evaluate the effects of withdrawal of long-leg braces (hip-knee-ankle-foot orthoses [HKAFO]) on activity and ambulation in children with osteogenesis imperfecta.

DESIGN

A prospective, randomized cross-over trial, that describes the effects of withdrawing HKAFO.

PATIENTS

Ten children who were ambulatory with the assistance of braces. All had type III or IV osteogenesis imperfecta. Children were paired for age and clinical severity. Strength testing, fractures, and independence in daily activity were monitored at 4-month intervals for 32 months (16 months each of braced and unbraced periods). Gait was analyzed during braced and unbraced conditions.

RESULTS

Muscle strength declined .35 grade during unbraced and .1 grade during braced intervals. Children spent more time in upright activity during braced intervals than during unbraced intervals (p = .17). Children were more independent in daily activities during braced than during unbraced periods (p = .14). Seventeen fractures of lower extremities occurred during all the unbraced periods, and 8 occurred during the braced intervals (p = .08); the fracture rate was higher during unbraced intervals. (p = .06) Bracing was associated with increased hip flexion and stride length and decreased transverse plane pelvic rotation.

CONCLUSION

Withdrawal of HKAFO in children with osteogenesis imperfecta who had achieved upright activity was not associated with significant decrease in muscle strength or independence, but there was an associated increase in fracture rate that nearly reached significance.

[Prenatal diagnosis of osteogenesis imperfecta. Two cases]

We report two cases of prenatal diagnosis of osteogenesis imperfecta (type S of Marotaux), diagnosed at 23 and 24 weeks of gestation, revealed by of an ultrasound scan which noted an abnormal femoral incurvation. The problem of differential diagnosis with other diseases causing femoral incurvation (notably campomelic dysplasia) is difficult, especially at early stage. This question is debated here. The interest to associate ultrasound scan and uterine contents radiography is so demonstrated.

The Nicholas Andry Award-1996. The molecular pathology of osteogenesis imperfecta

A systematic analysis of the molecular pathology of osteogenesis imperfecta was undertaken in 200 cases. The findings indicate that molecular defects of Type I collagen are the major cause of this disease. The mild form of osteogenesis imperfecta is caused by quantitative anomalies of Type I collagen. The other forms of the disease, which are more severe, are caused by quantitative and qualitative anomalies of Type I collagen. The mutant Type I collagen molecules are secreted poorly and are susceptible to intracellular and extracellular degradation with loss of normal and mutant collagen chains. The mutant molecules severely impair the formation of the extracellular matrix causing an abnormal architecture of dermis and bone. The molecular pathology was correlated with the clinical, radiologic, and pathologic features. As a result, the clinical classification was expanded and a new biochemical classification of osteogenesis imperfecta was developed.

Mutation producing alternative splicing of exon 26 in the COL1A2 gene causes type IV osteogenesis imperfecta with intrafamilial clinical variability

We have characterized a familial form of osteogenesis imperfecta (OI). Following the identification by ultrasound of short limbs and multiple fractures in a fetus at 25 weeks of gestation, the family was referred with a provisional diagnosis of severe OI. We detected subtle clinical and radiological signs of OI in the father and in the paternal grandmother of the proposita, who had never received a diagnosis of OI. Linkage analysis indicated COL1A2 as the disease locus. Heteroduplex analysis of reverse transcription-polymerase chain reaction (RT-PCR) amplification products of pro alpha2(I) mRNA from an affected member and subsequent sequencing of the candidate region demonstrated the presence of normal transcripts and a minority of transcripts lacking exon 26 (54 bp) of COL1A2. Sequencing of PCR-amplified genomic DNA identified an A --> G transition in the moderately conserved +3 position of the IVS 26 donor splice site. The mutant pre-mRNA molecules were alternatively spliced, yielding both full-length and deleted transcripts that represented less than 30% of the total pro alpha2(I) mRNA. The biochemical data on type I collagen synthesized by dermal fibroblasts showed intracellular retention of the mutant protein; failure to detect the shortened alpha2(I) chains either in the medium or in the cell layer may be the consequence of their instability at physiological temperature. These observations justified the mild resulting phenotype.

Osteogenesis imperfecta: clinical, cephalometric, and biochemical investigations of OI types I, III, and IV

The aim of the study was to analyze craniofacial development in 54 patients with osteogenesis imperfecta (OI), who were classified into OI types I, III, and IV according to clinical criteria, and to relate the findings to the abnormalities in collagen I production. In 33 patients, analysis of radioactively labelled procollagen was performed. Cephalometric radiographs, facial photographs, and CT-scans (a single case) were analyzed and mean facial diagrams for lateral and frontal films were produced based on registration of 221 reference points. Radiographs of 102 male and 51 female Danish students served as control material. In OI type I, size of the skull and jaws was generally slightly reduced, but morphology was within normal limits. In OI type IV and especially type III more severe abnormalities were found; the cranial base was flattened, the maxilla posteriorly inclined, and nearly all size-measurements were reduced. In OI type III the sagittal jaw relations were reduced and a mandibular overjet recorded. Three OI type I patients, whose fibroblasts produced structurally abnormal collagen I, had the stature and several features in the craniofacial region, which corresponded to those recorded for the OI type IV group. Also, in three OI type IV patients whose fibroblasts produced a reduced amount of normal collagen I, craniofacial morphology showed several features resembling type I patients. We conclude that structural abnormalities of collagen I generally give rise to more severe alterations of the craniofacial features than a quantitative defect of collagen I. OI type I patients are only slightly affected in their craniofacial region, while patients with OI type IV and especially type III are moderately to severely affected. The combined cephalometric and biochemical findings suggest that future classification of patients with osteogenesis imperfecta should be based on biochemical/molecular and radiological analyses in combination with clinical criteria rather than on clinical features alone.

Hearing loss (in nonoperated ears) in relation to age in osteogenesis imperfecta type I

Hearing loss was studied in relation to age in nonoperated ears in a group of 142 subjects with autosomal dominant osteogenesis imperfecta type I, which was compared to that in a random subsample of 70 subjects. In the n = 142 group, particularly below the age of 30 years, considerable selection (ie, for ear surgery) had occurred on hearing loss. The hearing threshold increased gradually with age. A hearing loss of greater than 30 dB (Fletcher index) was observed for 51% of the subjects older than 20 years and younger than 60 years. The median hearing loss progressed from the 10th to the 45th years of life with an average annual threshold increase (ATI) of 1 dB/y (0.5 to 4 kHz) up to 1.7 dB/y (8 kHz). Sensorineural loss accounted for 0.6 dB/y ATI at 0.5 to 4 kHz and 1.3 dB/y ATI at 8 kHz; conductive loss accounted for 0.4 dB/y ATI at all frequencies.

Non-accidental injury: confusion with temporary brittle bone disease and mild osteogenesis imperfecta

Accurate diagnosis of non-accidental injury (NAI) can be reached in the majority of cases by careful appraisal of the social and family history, combined with painstaking clinical roentgenographic and other imaging evaluations. Careful review of the scientific literature clearly indicates that collagen analysis to exclude mild forms of osteogenesis imperfecta, especially type IV, is recommended only in rare cases in which diagnosis of NAI remains in doubt even after thorough evaluation by experienced radiologists and/or other physicians. Until clinical research scientifically establishes the existence of temporary brittle bone disease, it should remain strictly a hypothetical entity and not an acceptable medical diagnosis.

Osteogenesis imperfecta in childhood: impairment and disability

OBJECTIVE

To determine clinical characteristics in children with osteogenesis imperfecta (OI) regarding impairment (range of joint motion and muscle strength) and disability (functional skills) in relation to the different types of the disease, and to study the correlation between characteristics of impairment and disability.

METHODS

In a cross-sectional study 54 children with OI (OI type I: 24; OI type III: 15; OI type IV: 15), the range of joint motion, muscle strength, and functional ability were measured in a standardized way and analyzed statistically.

RESULTS

The range of joint motion in almost all joints differed significantly with respect to the different disease types. In OI type I patients, generalized hypermobility of the joints was present, without decrease in joint motion. In OI type III the extremities were severely maligned, especially the lower limbs. In type IV the upper and lower extremities were equally maligned. Muscle strength differed significantly with respect to the different types of OI. In type I patients, muscle strength was normal except for the periarticular hip muscles. In type III, especially in the lower extremities, muscle strength was severely decreased, with a muscular imbalance around the hip joint. In type IV, muscle strength was mainly decreased in the proximal muscles of the upper and lower extremities. In children </=7.5 years of age, significant differences existed among the different disease types in functional skills regarding mobility. No significant difference was observed in self-care and social function, although the most severely affected children showed a tendency to score better with social function. Older children differed significantly concerning mobility and self-care items. In children </=7.5 years old, a correlation was sometimes observed between impairment and disability items, although in older children a moderate to good correlation was always present (r > .6).

CONCLUSION

In OI, severity-related profiles exist, within the different subtypes of the disease, regarding range of joint motion, muscle strength, and functional skills. In younger children, impairment parameters do not sufficiently correlate for disability. Rehabilitation strategies in younger children should therefore focus on improvement of functional skills and not only on impairment parameters.

Osteogenesis imperfecta

In the past 20 years, tremendous strides have been made in our understanding of the biochemical and genetic abnormalities associated with osteogenesis imperfecta (OI). Prenatal diagnostic techniques have allowed early detection of this disorder, particularly in families in which the actual molecular defect is already known. Although medical and surgical management of patients with OI continue to improve, the proper management of such problems as basilar impression still need to be determined. Progress in the treatment of OI at a molecular level is encouraging.

The surgical treatment of mandibular fractures in a child with osteogenesis imperfecta

The treatment of multiple mandibular fractures in an 8-year-old child suffering from osteogenesis imperfecta is described. The use of microplates is presented while some specific problems in relation to the disease are discussed.

Osteogenesis imperfecta and malignant hyperthermia. Is there a relationship?

We describe a patient with osteogenesis imperfecta who developed tachycardia, metabolic and respiratory acidosis (pH 7.14, PCO2 8.4 kPa, BE -8.5 mmol.l-1) and hyperthermia up to 40 degrees C during anaesthesia with barbiturates, fentanyl, pancuronium, and nitrous oxide. Malignant hyperthermia was suspected and the patient treated accordingly. Two years later the in-vitro contracture test for malignant hyperthermia was completely normal. We conclude that hypermetabolism in patients with osteogenesis imperfecta is due to unknown mechanisms other than malignant hyperthermia.