Osteogenesis imperfecta and cardiovascular diseases

Sclerostin inhibition in rare bone diseases: Molecular understanding and therapeutic perspectives

Sclerostin emerges as a novel target for bone anabolic therapy in bone diseases. Osteogenesis imperfecta (OI) and X-linked hypophosphatemia (XLH) are rare bone diseases in which therapeutic potential of sclerostin inhibition cannot be ignored. In OI, genetic/pharmacologic sclerostin inhibition promoted bone formation of mice, but responses varied by genotype and age. Serum sclerostin levels were higher in young OI-I patients, while lower in adult OI-I/III/IV. It's worth investigating whether therapeutic response of OI to sclerostin inhibition could be clinically predicted by genotype and age. In XLH, preclinical/clinical data suggested factors other than identified FGF23 contributing to XLH. Higher levels of circulating sclerostin were detected in XLH. Sclerostin inhibition promoted bone formation in Hyp mice, while restored phosphate homeostasis in age-/gender-dependent manner. The role of sclerostin in regulating phosphate metabolism deserves investigation. Sclerostin/FGF23 levels of XLH patients with/without response to FGF23-antibody warrants study to develop precise sclerostin/FGF23 inhibition strategy or synergistic/additive strategy. Notably, OI patients were associated with cardiovascular abnormalities, so were XLH patients receiving conventional therapy. Targeting sclerostin loop3 promoted bone formation without cardiovascular risks. Further, blockade of sclerostin loop3-LRP4 interaction while preserving sclerostin loop2-ApoER2 interaction could be a potential precise sclerostin inhibition strategy for OI and XLH with cardiovascular safety. The Translational Potential of this Article. Preclinical data on the molecular understanding of sclerostin inhibition in OI and therapeutic efficacy in mouse models of different genotypes, as well as clinical data on serum sclerostin levels in patients with different phenotypes of OI, were reviewed and discussed. Translationally, it would facilitate to develop clinical prediction strategies (e.g. based on genotype and age, not just phenotype) for OI patients responsive to sclerostin inhibition. Both preclinical and clinical data suggested sclerostin as another factor contributing to XLH, in addition to the identified FGF23. The molecular understanding and therapeutic effects of sclerostin inhibition on both promoting bone anabolism and improving phosphate homostasis in Hyp mice were reviewed and discussed. Translationaly, it would facilitate the development of precise sclerostin/FGF23 inhibition strategy or synergistic/additive strategy for the treatment of XLH. Cardiovascular risk could not be ruled out during sclerostin inhibition treatment, especially for OI and XLH patients with cardiovascular diseases history and cardiovascular abnormalities. Studies on the role of sclerostin in inhiting bone formation and protecting cardiovascular system were reviewed and discussed. Translationaly, blockade of sclerostin loop3-LRP4 interaction while preserving sclerostin loop2-ApoER2 interaction could be a potential precise sclerostin inhibition strategy for OI and XLH with cardiovascular safety.

Reduced Retinal Blood Vessel Densities Measured by Optical Coherence Tomography Angiography in Keratoconus Patients Are Negatively Correlated with Keratoconus Severity

Keratoconus (KC) is the most common corneal ectasia. Optical coherence tomography angiography (OCT-A) is a relatively new non-invasive imaging technique that allows the visualization and quantification of retinal and choriocapillary blood vessels. The aim of this study is to assess retinal and choriocapillary vessel density (VD) differences between KC patients and healthy controls and to investigate correlations between VD and KC severity. Fifty-two eyes were included in this exploratory study: twenty-six eyes from 26 KC patients and twenty-six eyes from 26 age- and gender-matched healthy controls. All patients underwent Scheimpflug corneal topography with Pentacam, axis lengths measurement and optical coherence tomography angiography (OCT-A). The thinnest spot in corneal pachymetry, maximum K (Kmax) and KC severity indices from the Belin/Ambrósio enhanced ectasia display (BAD) were also assessed. There was a distinct reduction particularly in the retinal VD of the superficial capillary plexus (SCP). Correlation analyses showed strong and moderate negative correlations between the VD in the macular SCP and BAD KC scores and between the SCP VD and Kmax. There was no difference in retinal thickness between the KC and healthy controls. With this study, further evidence for altered VD measurements by OCT-A in KC patients is given. For the first time, we demonstrated negative correlations between BAD KC scores and retinal blood vessel alterations. A major limitation of the study is the relatively small sample size. Since an artefactual reduction of the quantitative OCT-A measurements due to irregular corneal topography in KC must be assumed, it remains to be investigated whether there are also actual changes in the retinal microcirculation in KC.

Bleeding assessment in a large cohort of patients with Osteogenesis Imperfecta

BACKGROUND

Osteogenesis Imperfecta (OI) is characterised by bone fragility. Among several features, easy bruising and multiple case reports on haemorrhagic events have been reported. This paper describes the diverse manifestations of bleeding and bruising in a large cohort of 328 OI patients. The aim of this study is to provide insight in the diverse aspects and therapeutic considerations of bleedings in OI.

METHODS

This descriptive cohort study was conducted at the National Expert Center for adults with OI in the Netherlands. Bleeding was assessed by the validated self-bleeding assessment tool (Self-BAT) The tool was distributed among 328 adults with different clinically confirmed types of OI.

RESULTS

195 of 328 invited patients (completion rate 60%) with OI type 1 (n = 144), OI type 3 (n = 17) and OI type 4 (n = 34), aged between 18 and 82 years, completed the tool. Self-BAT scores were above the normal range in 42% of all patients. For males Self-BAT scores were increased in 37% with a mean score of 3.7, ranged between 0 and 18. For females the Self-BAT scores were increased in 44% with a mean of 5.4 and a range of 0-24. No statistical differences in OI subtypes were found.

CONCLUSIONS

Bleeding tendency appears to be a relevant complication in OI patients as this study confirms the presumption of bleeding tendency. There are specific recommendations to clinicians who treat OI patients to consider an assessment of bleeding tendency and use potential interventions to reduce haemorrhagic complications and improve quality of life.

Osteogenesis Imperfecta Type 3 in a 10-Year-Old Child With Acute Respiratory Distress Syndrome

Osteogenesis imperfecta (OI) represents a group of rare connective tissue disorders characterized by excessive bone fragility. Type 3 is a rare form with new mutations; osteopenia and bone fragility are significant with numerous fractures, continuous and severe deformity of the spine, and long bones. Our case study concerns a 10-year-old male child admitted to the pediatric department of the State University of Haiti Hospital. OI type 3 was diagnosed based on both clinical and radiological assessments. Multidisciplinary care was initiated. Although the evolution was still unsatisfactory, characterized by intermittent episodes of dyspnea and left lung hypoplasia, he was stabilized after 28 days of hospitalization and referred to the orthopedics department for follow-up care.

Mitral Regurgitation and Heart Failure as the First Presentation in a Patient with Features of Two Connective Tissue Disorders: A Rare Combination of Mucopolysaccharidosis and Osteogenesis Imperfecta?

Connective tissue disorders sometimes involve cardiovascular systems. This report describes the case of a middle-aged man with mitral regurgitation and heart failure. He had distinctive features of mucopolysaccharidosis type (MPS) III, but no gene mutations that were known to be associated with MPS. Meanwhile, he had a COL1A2 gene mutation that is associated with osteogenesis imperfecta (OI), and had some features that were compatible with OI. The patient might have had a rare connective tissue disorder with the characteristics of MPS III and OI, which was initially detected as a result of the cardiovascular manifestations.

Challenges of Fracture Management for Adults With Osteogenesis Imperfecta

Osteogenesis imperfecta is caused by qualitative or quantitative defects in type I collagen. Although often considered a disease with primarily pediatric manifestations, more than 25% of lifetime fractures are reported to occur in adulthood. General care of adults with osteogenesis imperfecta involves measures to preserve bone density, regular monitoring of hearing and dentition, and maintenance of muscle strength through physical therapy. Surgical stabilization of fractures in these patients can be challenging because of low bone mineral density, preexisting skeletal deformities, or obstruction by instrumentation from previous surgeries. Additionally, unique perioperative considerations exist when operatively managing fractures in patients with osteogenesis imperfecta. To date, there is little high-quality literature to help guide the optimal treatment of fractures in adult patients with osteogenesis imperfecta. [Orthopedics. 2017; 40(1):e17-e22.].

[Peripheral artery disease in patients younger than 50 years old: Which etiology?]

Peripheral arterial disease (PAD) encompasses disease of all arteries of the body except the coronary arteries. The main etiology whatever the patient's age is atherosclerosis. Different etiologies can induce PAD especially when patients are younger than 50 years old and have no cardiovascular risk factors (smoking, hypertension, diabetes…). PAD that appears before 50 years old can be named juvenile PAD (JPAD) although there is no consensus about the definition. The aim of this work is to present the different etiologies of JPAD according to their hereditary, acquired or mixed origins. The following hereditary causes are addressed: Marfan syndrome, Ehlers-Danlos syndrome, homocystinuria, pseudoxanthoma elasticum, osteogenesis imperfecta "mid-aortic" syndrome. Among the acquired etiologies, inflammatory JPADs without extravascular signs such as atherosclerosis and Buerger's disease, inflammatory JPADs with extravascular signs as Takayasu's disease, Behçet's disease and Cogan's syndrome, JPADs like aortitis, embolic JPADs, iatrogenic JPADs, and mechanical or traumatic JPADs are described. Finally, mixed origins as thrombotic disease and fibromuscular dysplasia are presented. This work will assist clinicians in the diagnosis of JPAD.

Weight loss surgery improves quality of life in pediatric patients with osteogenesis imperfecta

BACKGROUND

Osteogenesis imperfecta (OI) is an inherited disorder, which causes brittle bones resulting in recurrent fractures. The associated poor mobility of children with OI increases susceptibility to obesity, and obesity further dramatically limits mobility and increases fracture risk.

OBJECTIVES

The aim of this report is to describe outcomes of weight loss surgery (WLS) in 2 adolescents with severe obesity and OI.

SETTING

Two University Hospitals (in the United Kingdom and in the United States).

METHODS

Two cases of OI treated with WLS were identified. Pre- and postoperative anthropometric and biochemical data and clinical course were reviewed.

RESULTS

In these 2 cases, preoperative Body Mass Index (BMI) values were 38 and 46 kg/m². Following laparoscopic sleeve gastrectomy (LSG), BMI decreased by 55% and 60% by 26 and 24 months, respectively. There were no surgical complications, and both patients experienced improvement in their mobility and ability to perform activities of daily living.

CONCLUSION

WLS effectively treated severe obesity in 2 OI patients and substantially improved mobility and quality of life, theoretically reducing fracture risk.

Prevalence of Cardiovascular Disease and Cardiac Symptoms: Left and Right Ventricular Function in Adults With Osteogenesis Imperfecta

BACKGROUND

Osteogenesis imperfecta (OI), also known as brittle bone disease or Lobstein syndrome, is a congenital bone disorder characterized by brittle bones that are prone to fracture. People with OI are born with defective connective tissue in most cases secondary to a deficiency of type-I collagen, which represents approximately 75% of total collagen in the adult myocardium. The purpose of our study was to assess the prevalence of cardiomyopathy, electrocardiogram (ECG) abnormalities, and cardiovascular symptoms among patients with OI.

METHODS

We studied 99 adults with OI from the national OI registry in Norway. Patients were divided into type I, III, and IV, and 52 control subjects. History and physical examination, ECG, and echocardiographic parameters of left ventricular (LV) and right ventricular (RV) systolic and diastolic function were obtained.

RESULTS

ECG abnormalities and cardiac symptoms were more common among patients with OI. RV and LV systolic peak velocity were significantly lower and diastolic mitral tricuspid valve wave and early diastolic tissue Doppler velocity ratio increased in the OI group compared with the control subjects; 5.7 ± 1.2 vs 6.3 ± 1.2 cm/s (P < 0.05) and 8 ± 1.8 vs 9.5 ± 1.4 cm/s (P < 0.05) and 9.8 ± 2.6 vs 7.4 ± 2.0 (P < 0.05) and 8.6 ± 3.3 vs 6.1 ± 1.4, respectively. In multivariate analysis OI was found to be an independent risk factor for RV systolic and diastolic dysfunction.

CONCLUSIONS

Cardiac symptoms and ECG changes are common among patients with OI. Our study findings suggest RV and LV systolic and diastolic function to be impaired in patients with OI compared with normal individuals. In multivariate analysis, however, OI was an independent predictor only of reduced RV systolic and diastolic function.

Multi-modality guided trans-apical closure of recurrent mitral para-valvular regurgitation after failed surgical management in a patient with osteogenesis imperfecta

We report a case of a 54 year-old man with osteogenesis imperfecta who developed severe para-valvular mitral regurgitation after a second heart operation to correct the same problem. The large para-valvular leak was successfully closed with an Amplatzer Vascular Plug III delivered from the apical approach.

Subarachnoid hemorrhage secondary to a ruptured middle cerebral aneurysm in a patient with osteogenesis imperfecta: a case report

Background

Osteogenesis imperfecta (OI) is a heterogeneous group of inherited disorders that occur owing to the abnormalities in type 1 collagen, and is characterized by increased bone fragility and other extraskeletal manifestations. We report the case of a patient who was diagnosed with OI following subarachnoid hemorrhage (SAH) secondary to a ruptured saccular intracranial aneurysm (IA).

Case Presentation

A 37-year-old woman was referred to our hospital because of sudden headache and vomiting. She was diagnosed with SAH (World Federation of Neurosurgical Society grade 2) owing to an aneurysm of the middle cerebral artery. She then underwent surgical clipping of the aneurysm successfully. She had blue sclerae, a history of several fractures of the extremities, and a family history of bone fragility and blue sclerae in her son. According to these findings, she was diagnosed with OI type 1. We performed genetic analysis for a single nucleotide G/C polymorphism (SNP) of exon 28 of the gene encoding for alpha-2 polypeptide of collagen 1, which is a potential risk factor for IA. However, this SNP was not detected in this patient or in five normal control subjects. Other genetic analyses did not reveal any mutations of the COL1A1 or COL1A2 gene. The cerebrovascular system is less frequently involved in OI. OI is associated with increased vascular weakness owing to collagen deficiency in and around the blood vessels. SAH secondary to a ruptured IA with OI has been reported in only six cases.

Conclusion

The patient followed a good clinical course after surgery. It remains controversial whether IAs are caused by OI or IAs are coincidentally complicated with OI.

Redox imbalance and morphological changes in skin fibroblasts in typical Rett syndrome

Evidence of oxidative stress has been reported in the blood of patients with Rett syndrome (RTT), a neurodevelopmental disorder mainly caused by mutations in the gene encoding the Methyl-CpG-binding protein 2. Little is known regarding the redox status in RTT cellular systems and its relationship with the morphological phenotype. In RTT patients (n = 16) we investigated four different oxidative stress markers, F2-Isoprostanes (F2-IsoPs), F4-Neuroprostanes (F4-NeuroPs), nonprotein bound iron (NPBI), and (4-HNE PAs), and glutathione in one of the most accessible cells, that is, skin fibroblasts, and searched for possible changes in cellular/intracellular structure and qualitative modifications of synthesized collagen. Significantly increased F4-NeuroPs (12-folds), F2-IsoPs (7.5-folds) NPBI (2.3-folds), 4-HNE PAs (1.48-folds), and GSSG (1.44-folds) were detected, with significantly decreased GSH (-43.6%) and GSH/GSSG ratio (-3.05 folds). A marked dilation of the rough endoplasmic reticulum cisternae, associated with several cytoplasmic multilamellar bodies, was detectable in RTT fibroblasts. Colocalization of collagen I and collagen III, as well as the percentage of type I collagen as derived by semiquantitative immunofluorescence staining analyses, appears to be significantly reduced in RTT cells. Our findings indicate the presence of a redox imbalance and previously unrecognized morphological skin fibroblast abnormalities in RTT patients.

Ventricular septal defect closure in a child with osteogenesis imperfecta: risk factors and management

Cardiac surgery in patients with osteogenesis imperfecta is challenging as the friability of the tissues can be hazardous before, during, and after the operation. A multidisciplinary approach with a planned strategy is essential for the successful management of these patients. We present a 6-year old child with osteogenesis imperfecta, who underwent ventricular septal defect closure without any complication.

Valvular and aortic diseases in osteogenesis imperfecta

Osteogenesis imperfecta (OI) is an inheritable connective tissue disorder caused by defective collagen synthesis with the principal manifestations of bone fragility. OI has been associated with left sided valvular regurgitation and aortic dilation. Valve and aortic surgery are technically feasible in patients with OI but are inherently high risk due to the underlying connective tissue defect. This report reviews the valvular and aortic pathology associated with OI and their management. We describe two cases of patients with OI who have significant aortic and mitral valve regurgitation, one of whom has been managed conservatively and the other who has undergone successful mitral valve repair and aortic valve replacement. The latter case represents the fifth case of mitral valve repair in a patient with OI reported in the medical literature.

Cardiopulmonary dysfunction in the Osteogenesis imperfecta mouse model Aga2 and human patients are caused by bone-independent mechanisms

Osteogenesis imperfecta (OI) is an inherited connective tissue disorder with skeletal dysplasia of varying severity, predominantly caused by mutations in the collagen I genes (COL1A1/COL1A2). Extraskeletal findings such as cardiac and pulmonary complications are generally considered to be significant secondary features. Aga2, a murine model for human OI, was systemically analyzed in the German Mouse Clinic by means of in vivo and in vitro examinations of the cardiopulmonary system, to identify novel mechanisms accounting for perinatal lethality. Pulmonary and, especially, cardiac fibroblast of perinatal lethal Aga2/+ animals display a strong down-regulation of Col1a1 transcripts in vivo and in vitro, resulting in a loss of extracellular matrix integrity. In addition, dysregulated gene expression of Nppa, different types of collagen and Agt in heart and lung tissue support a bone-independent vicious cycle of heart dysfunction, including hypertrophy, loss of myocardial matrix integrity, pulmonary hypertension, pneumonia and hypoxia leading to death in Aga2. These murine findings are corroborated by a pediatric OI cohort study, displaying significant progressive decline in pulmonary function and restrictive pulmonary disease independent of scoliosis. Most participants show mild cardiac valvular regurgitation, independent of pulmonary and skeletal findings. Data obtained from human OI patients and the mouse model Aga2 provide novel evidence for primary effects of type I collagen mutations on the heart and lung. The findings will have potential benefits of anticipatory clinical exams and early intervention in OI patients.

Myocardial involvement in patients with osteogenesis imperfecta

Mitral and aortic valve regurgitation is commonly found in osteogenesis imperfecta (OI) patients, however, little is known about the myocardial involvement in this disorder. An 82-year-old man with OI developed heart failure and was admitted to our hospital. Echocardiogram revealed severe mitral regurgitation without left ventricular (LV) dilatation, but with LV wall thickening. Histological analysis exhibited interstitial fibrosis of the myocardium in addition to myxoid changes of the mitral leaflet. These findings suggest that OI patients may develop LV remodeling together with diastolic dysfunction.

Aortic root and hemiarch replacement in osteogenesis imperfecta

We describe a case of osteogenesis imperfecta in a 52-year-old man who underwent successful repair of aortic root dilatation and aortic valve insufficiency, using a bioprosthetic aortic valve anastomosed to an interposition graft.

A collagen α2(I) mutation impairs healing after experimental myocardial infarction

Collagen breakdown and de novo synthesis are important processes during early wound healing after myocardial infarction (MI). We tested the hypothesis that collagen I, the main constituent of the extracellular matrix, affects wound healing after MI. The osteogenesis imperfecta mouse (OIM), lacking procollagen-α2(I) expression, represents a model of the type III form of the disease in humans. Homozygous (OIM/OIM), heterozygous (OIM/WT), and wild-type (WT/WT) mice were subjected to a permanent myocardial infarction protocol or sham surgery. Baseline functional and geometrical parameters determined by echocardiography did not differ between genotypes. After MI but not after sham surgery, OIM/OIM animals exhibited significantly increased mortality, due to early ventricular rupture between day 3 and 7. Echocardiography at day 1 demonstrated increased left ventricular dilation in OIM/OIM animals. Less collagen I mRNA within the infarct area was found in OIM/OIM animals. At 2 days after MI, MMP-9 expression in the infarct border zone was higher in OIM/OIM than in WT/WT animals. Increased granulocyte infiltration into the infarct border zone occurred in OIM/OIM animals. Neither granulocyte depletion nor MMP inhibition reduced mortality in OIM/OIM animals. In this murine model, deficiency of collagen I leads to a myocardial wound-healing defect. Both structural alterations within pre-existing collagen matrix and impaired collagen de novo expression contribute to a high rate of early myocardial rupture after MI.

Inflammatory regulation of valvular remodeling: the good(?), the bad, and the ugly

Heart valve disease is unique in that it affects both the very young and very old, and does not discriminate by financial affluence, social stratus, or global location. Research over the past decade has transformed our understanding of heart valve cell biology, yet still more remains unclear regarding how these cells respond and adapt to their local microenvironment. Recent studies have identified inflammatory signaling at nearly every point in the life cycle of heart valves, yet its role at each stage is unclear. While the vast majority of evidence points to inflammation as mediating pathological valve remodeling and eventual destruction, some studies suggest inflammation may provide key signals guiding transient adaptive remodeling. Though the mechanisms are far from clear, inflammatory signaling may be a previously unrecognized ally in the quest for controlled rapid tissue remodeling, a key requirement for regenerative medicine approaches for heart valve disease. This paper summarizes the current state of knowledge regarding inflammatory mediation of heart valve remodeling and suggests key questions moving forward.

Aortic valve disease and treatment: the need for naturally engineered solutions

The aortic valve regulates unidirectional flow of oxygenated blood to the myocardium and arterial system. The natural anatomical geometry and microstructural complexity ensures biomechanically and hemodynamically efficient function. The compliant cusps are populated with unique cell phenotypes that continually remodel tissue for long-term durability within an extremely demanding mechanical environment. Alteration from normal valve homeostasis arises from genetic and microenvironmental (mechanical) sources, which lead to congenital and/or premature structural degeneration. Aortic valve stenosis pathobiology shares some features of atherosclerosis, but its final calcification endpoint is distinct. Despite its broad and significant clinical significance, very little is known about the mechanisms of normal valve mechanobiology and mechanisms of disease. This is reflected in the paucity of predictive diagnostic tools, early stage interventional strategies, and stagnation in regenerative medicine innovation. Tissue engineering has unique potential for aortic valve disease therapy, but overcoming current design pitfalls will require even more multidisciplinary effort. This review summarizes the latest advancements in aortic valve research and highlights important future directions.

[Bilateral spontaneous carotid artery dissection in osteogenesis imperfecta (type I)]

We report on a 36-year-old patient with an acute cerebral infarction due to a spontaneous dissection of both internal carotid arteries in conjunction with type I osteogenesis imperfecta. Spontaneous dissections of cerebral arteries (DCA) represent a common cause of cerebral infarctions in younger patients. Our case shows that a hereditary connective tissue disorder should be considered in all patients with "spontaneous" DCA. The identification of an - initially unknown - hereditary connective tissue disorder may con-tribute to primary and secondary prophylaxis of cerebral ischemia.

Heart valve development: regulatory networks in development and disease

In recent years, significant advances have been made in the definition of regulatory pathways that control normal and abnormal cardiac valve development. Here, we review the cellular and molecular mechanisms underlying the early development of valve progenitors and establishment of normal valve structure and function. Regulatory hierarchies consisting of a variety of signaling pathways, transcription factors, and downstream structural genes are conserved during vertebrate valvulogenesis. Complex intersecting regulatory pathways are required for endocardial cushion formation, valve progenitor cell proliferation, valve cell lineage development, and establishment of extracellular matrix compartments in the stratified valve leaflets. There is increasing evidence that the regulatory mechanisms governing normal valve development also contribute to human valve pathology. In addition, congenital valve malformations are predominant among diseased valves replaced late in life. The understanding of valve developmental mechanisms has important implications in the diagnosis and management of congenital and adult valve disease.

Valvular heart disease in osteogenesis imperfecta: presentation of a case and review of the literature

Osteogenesis imperfecta (OI) is a rare inheritable disorder of connective tissue. While musculoskeletal abnormalities are well known, cardiovascular involvement is rare. Aortic root dilation is the most common cardiovascular manifestation. OI preferentially affects the left-sided heart valves, for unclear reasons, leading to aortic and mitral regurgitation. Valve replacement surgery carries a unique set of issues in this population, and fewer than 40 cases have been reported. We report a case of chronic severe aortic regurgitation in a patient with OI complicated by the development of a flail aortic valve leaflet and presenting with a transient ischemic attack. The patient subsequently underwent successful combined bioprosthetic aortic valve replacement and coronary artery bypass grafting. We review the literature on valvular disease and other cardiovascular manifestations in OI and the related surgical considerations relevant to this patient population.

Ostéogenèse imparfaite

Osteogenesis imperfecta is a genetic disorder that causes increased bone fragility and low bone mass. Osteogenesis imperfecta is a rare disease: its estimated prevalence is between 1/10000 and 1/20000 persons. The severity of skeletal and extraskeletal manifestations varies widely. Most patients have a mutation in one of the 2 genes that encode the alpha chains of collagen type I. Treatment with bisphosphonates has produced clear improvements, especially for growing children. The appropriate regimen for bisphosphonate treatment remains to be determined: the goal is to find the lowest effective dose to minimize side effects. Treatment of osteogenesis imperfecta must be multidisciplinary, including physicians, surgeons, and physical therapists.

Ruptured Cerebral Artery Aneurysm and Bacterial Meningitis in a Man With Osteogenesis Imperfecta

This report describes a 38-year-old man with osteogenesis imperfecta who died of a ruptured cerebral artery aneurysm and bacterial meningitis. He had multiple long bone fractures in the past, and approximately 4 months before death, he had surgery to relieve symptoms of basilar impression. The surgery was complicated by a postoperative wound infection. For the next 4 months, he had intermittent headaches and vomiting. He was found dead in his bed at home. At autopsy, he had a ruptured anterior communicating artery aneurysm and bacterial meningitis. Cerebrospinal fluid and blood cultures had growth of Staphylococcus aureus. Osteogenesis imperfecta is a disorder of type I collagen. Type I collagen is present in many tissues, including blood vessels. The etiology of cerebral artery aneurysm formation is multifactorial. Some patients with cerebral artery aneurysms have been shown to have abnormalities in type III collagen. There has not been a reported relationship made between abnormalities in type I collagen and aneurysms. Meningitis can also result in cerebral artery aneurysms, but they are usually due to Aspergillus or Mycobacterium species. The case we report is unique; cerebral artery aneurysm formation may have been due to osteogenesis imperfecta and/or bacterial meningitis.

Cardiopulmonary fitness and muscle strength in patients with osteogenesis imperfecta type I

OBJECTIVE

To evaluate cardiopulmonary function, muscle strength, and cardiopulmonary fitness (VO 2 peak) in patients with osteogenesis imperfecta (OI).

STUDY DESIGN

In 17 patients with OI type I (mean age 13.3 +/- 3.9 years) cardiopulmonary function was assessed at rest using spirometry, plethysmography, electrocardiography, and echocardiography. Exercise capacity was measured using a maximal exercise test on a bicycle ergometer and an expired gas analysis system. Muscle strength in shoulder abductors, hip flexors, ankle dorsal flexor, and grip strength were measured. All results were compared with reference values.

RESULTS

Cardiopulmonary function at rest was within normal ranges, but when it was compared with normal height for age and sex, vital capacities were reduced. Mean absolute and relative VO 2 peak were respectively -1.17 (+/- 0.67) and -1.41 (+/- 1.52) standard deviations lower compared with reference values ( P < .01). Muscle strength also was significantly reduced in patients with OI, ranging from -1.24 +/- 1.40 to -2.88 +/- 2.67 standard deviations lower compared with reference values.

CONCLUSIONS

In patients with OI type I, no pulmonary or cardiac abnormalities at rest were found. The exercise tolerance and muscle strength were significantly reduced in patients with OI, which might account for their increased levels of fatigue during activities of daily living.

Aortic Valve Replacement in Osteogenesis Imperfecta-Technical and Practical Considerations for a Successful Outcome

Osteogenesis imperfecta is a connective tissue disorder that is rarely associated with isolated aortic insufficiency. Surgery on such patients carries high morbidity and mortality, which are mostly associated with bleeding tendencies secondary to increased tissue and capillary fragility. We report a 42-year-old male with isolated aortic incompetence, who underwent aortic valve replacement (AVR) with a mechanical prosthesis. The postoperative course was uneventful, and the patient was discharged home on the seventh postoperative day (POD 7). He remains well on follow-up 6 months later. We highlight the importance of a meticulous surgical technique, together with a strategy for management of anticipated perioperative complications to ensure a successful outcome.

Recombinant factor VIIa after aortic valve replacement in a patient with osteogenesis imperfecta

A 26-year-old man with osteogenesis imperfecta and severe aortic regurgitation was scheduled for aortic valve replacement. As previously described by other authors the operation was difficult owing to the friability and weakness of the tissues. Mean blood losses of 153 mL per hour during the first 7 postoperative hours were observed. Despite normal coagulation indicators the bleeding did not stop and recombinant factor VIIa was applied at 40 microg/kg. Bleeding was successfully stopped after this single application.

Myocardial mechanics and collagen structure in the osteogenesis imperfecta murine (oim)

Because the amount and structure of type I collagen are thought to affect the mechanics of ventricular myocardium, we investigated myocardial collagen structure and passive mechanical function in the osteogenesis imperfecta murine (oim) model of pro-alpha2(I) collagen deficiency, previously shown to have less collagen and impaired biomechanics in tendon and bone. Compared with wild-type littermates, homozygous oim hearts exhibited 35% lower collagen area fraction (P:<0.05), 38% lower collagen fiber number density (P:<0.05), and 42% smaller collagen fiber diameter (P:<0.05). Compared with wild-type, oim left ventricular (LV) collagen concentration was 45% lower (P:<0.0001) and nonreducible pyridinoline cross-link concentration was 22% higher (P:<0.03). Mean LV volume during passive inflation from 0 to 30 mm Hg in isolated hearts was 1.4-fold larger for oim than wild-type (P:=NS). Uniaxial stress-strain relations in resting right ventricular papillary muscles exhibited 60% greater strains (P:<0.01), 90% higher compliance (P:=0.05), and 64% higher nonlinearity (P:<0.05) in oim. Mean opening angle, after relief of residual stresses in resting LV myocardium, was 121+/-9 degrees in oim compared with 45+/-4 degrees in wild-type (P:<0.0001). Mean myofiber angle in oim was 23+/-8 degrees greater than wild-type (P:<0.02). Decreased myocardial collagen diameter and amount in oim is associated with significantly decreased fiber and chamber stiffness despite modestly increased collagen cross-linking. Altered myofiber angles and residual stress may be beneficial adaptations to these mechanical alterations to maintain uniformity of transmural fiber strain. In addition to supporting and organizing myocytes, myocardial collagen contributes directly to ventricular stiffness at high and low loads and can influence stress-free state and myofiber architecture.

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 and other heritable disorders of bone

This chapter summarizes the many recent advances in our understanding of the principal heritable disorders of bone. In the course of little more than a decade many diseases that were recognizable only by their clinical and radiological features have become explicable in molecular terms. Large numbers of mutations of the genes coding for collagen, for alkaline phosphatase, for the cell surface receptors for parathyroid hormone and for calcium, and for a number of other proteins, are recognized. The chapter covers the many variants of osteogenesis imperfecta, the most common heritable cause of fractures. It also covers osteopetrosis, hypophosphatasia, pseudohypoparathyroidism (with Albright's hereditary osteodystrophy), familial benign hypercalcaemia, autosomal dominant hypocalcaemia and the molecular causes of some chondrodysplasias.

Type III collagen is crucial for collagen I fibrillogenesis and for normal cardiovascular development

Type III collagen is a fibrillar forming collagen comprising three alpha1(III) chains and is expressed in early embryos and throughout embryogenesis. In the adult, type III collagen is a major component of the extracellular matrix in a variety of internal organs and skin. Mutations in the COL3A1 gene have been implicated as a cause of type IV Ehlers-Danlos syndrome, a disease leading to aortic rupture in early adult life. To directly study the role of Col3a1 in development and disease, we have inactivated the Col3a1 gene in embryonic stem cells by homologous recombination. The mutated allele was transmitted through the mouse germ line and homozygous mutant animals were derived from heterozygous intercrosses. About 10% of the homozygous mutant animals survived to adulthood but have a much shorter life span compared with wild-type mice. The major cause of death of mutant mice was rupture of the major blood vessels, similar to patients with type IV Ehlers-Danlos syndrome. Ultrastructural analysis of tissues from mutant mice revealed that type III collagen is essential for normal collagen I fibrillogenesis in the cardiovascular system and other organs.