Osteogenesis Imperfecta: Current and Prospective Therapies

Osteogenesis Imperfecta (OI) is a group of connective tissue disorders with a broad range of phenotypes characterized primarily by bone fragility. The prevalence of OI ranges from about 1:15,000 to 1:20,000 births. Five types of the disease are commonly distinguished, ranging from a mild (type I) to a lethal one (type II). Types III and IV are severe forms allowing survival after the neonatal period, while type V is characterized by a mild to moderate phenotype with calcification of interosseous membranes. In most cases, there is a reduction in the production of normal type I collagen (col I) or the synthesis of abnormal collagen as a result of mutations in col I genes. Moreover, mutations in genes involved in col I synthesis and processing as well as in osteoblast differentiation have been reported. The currently available treatments try to prevent fractures, control symptoms and increase bone mass. Commonly used medications in OI treatment are bisphosphonates, Denosumab, synthetic parathyroid hormone and growth hormone for children therapy. The main disadvantages of these therapies are their relatively weak effectiveness, lack of effects in some patients or cytotoxic side effects. Experimental approaches, particularly those based on stem cell transplantation and genetic engineering, seem to be promising to improve the therapeutic effects of OI.

Developmental charts for children with osteogenesis imperfecta, type I (body height, body weight and BMI)

Osteogenesis imperfecta (OI) is a rare genetic disorder of type I collagen. Type I is the most common, which is called a non-deforming type of OI, as in this condition, there are no major bone deformities. This type is characterised by blue sclera and vertebral fractures, leading to mild scoliosis. The body height of these patients is regarded as normal, or only slightly reduced, but there are no data proving this in the literature. The aim of this study is the preparation of the developmental charts of children with OI type I. The anthropometric data of 117 patients with osteogenesis imperfecta were used in this study (61 boys and 56 girls). All measurements were pooled together into one database (823 measurements in total). To overcome the problem of the limited number of data being available in certain age classes and gender groups, the method called reverse transformation was used. The body height of the youngest children, aged 2 and 3 years, is less than that of their healthy peers. Children between 4 and 7 years old catch up slightly, but at later ages, development slows down, and in adults, the median body height shows an SDS of -2.7.

CONCLUSION

These results show that children with type I OI are smaller from the beginning than their healthy counterparts, their development slows down from 8 years old, and, ultimately, their body height is impaired. What is Known: • The body height of patients with osteogenesis imperfecta type I is regarded as normal, or only slightly reduced, but in the known literature, there is no measurement data supporting this opinion. What is New: • Children with type I osteogenesis imperfecta are smaller from the beginning than their healthy counterparts, their development slows down from 8 years old and, ultimately, their final body height is impaired. • The developmental charts for the body height, body weight and BMI of children with type I osteogenesis imperfecta are shown.

Advances in the Classification and Treatment of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a rare disorder of type 1 collagen with 13 currently identified types attributable to inherited abnormalities in type 1 collagen amount, structure, or processing. The disease is characterized by an increased susceptibility to bony fracture. In addition to the skeletal phenotype, common additional extraskeletal manifestations include blue sclerae, dentinogenesis imperfecta, vascular fragility, and hearing loss. Medical management is focused on minimizing the morbidity of fractures, pain, and bone deformities by maximizing bone health. Along with optimizing Vitamin D status and calcium intake and physical/occupational therapy, individualized surgical treatment may be indicated. Pharmacological therapy with bisphosphonate medications is now routinely utilized for moderate to severe forms and appears to have a good safety profile and bone health benefits. New therapies with other anti-resorptives as well as anabolic agents and transforming growth factor (TGF)β antibodies are in development. Other potential treatment modalities could include gene therapy or mesenchymal cell transplant. In the future, treatment choices will be further individualized in order to reduce disease morbidity and mortality.

Genetics of Osteoporosis in Children

In the pathogenesis of paediatric osteoporosis, genetic causes may play an important role. The most prevalent monogenic cause of paediatric osteoporosis is osteogenesis imperfecta, a disorder characterised primarily by liability to fractures. With regard to diagnosis or exclusion of a monogenic cause of paediatric osteoporosis, clinical practice has changed rapidly in recent years. This is largely due to the discovery of many new genetic causes in patients with a clear clinical diagnosis of osteogenesis imperfecta but also due to the identification of genetic causes in patients with isolated or non-syndromal osteoporosis with fractures. In this chapter, known monogenic causes of syndromal and non-syndromal osteoporosis in children will be described. Furthermore, we will discuss when to refer for clinical genetic evaluation as well as the current and future merits of genetic evaluation of children with osteoporosis.

Primary Osteoporosis

Primary osteoporosis in childhood encompasses a range of bone fragility conditions that typically have a genetic origin. Understanding of the pathophysiology and genetics of primary osteoporosis has increased dramatically over the past 10 years. The clinical manifestations and consequences of the disease range from mild to severe, with the degree of growth retardation and bony deformity reflecting the severity and the underlying pathology. In children, primary osteoporosis is most commonly caused by one of the forms of osteogenesis imperfecta, which comprises a group of disorders characterised by abnormalities in type I collagen synthesis or processing. Diagnosis of any primary osteoporotic condition depends on the clinical history and examination but may be supported by other investigations, including various imaging techniques, histology and genetic analyses. Good management requires a multidisciplinary approach involving paediatricians, surgeons and allied health professionals, amongst others. Bisphosphonate therapy has revolutionised the approach to management and has positively modified outcomes for many children and their families. Physiotherapy and occupational therapy are the keys to optimising independence in mobility and daily living. Surgery is required in many severe cases to straighten limbs or stabilise the spine. Bisphosphonates remain the mainstay of medical treatment, but there are a number of alternative therapeutic agents under investigation that may further improve management of primary osteoporosis in children over the coming years.

[Clinical condition and therapy of bone diseases]

Skeletal dysplasia is the term which represents disorders including growth and differentiation of bone, cartilage and ligament. A lot of diseases are included, and new disorders have been added. However, the therapy of most bone diseases is less well-established. Achondroplasia, hypochondroplasia, and osteogenesis imperfecta are most frequent bone diseases. There is no curative treatment for these diseases, however, supportive therapies are available ; for example, growth-hormone therapy for achondroplasia and hypochondroplasia, and bisphosphonate therapy for osteogenesis imperfecta. In addition, enzyme replacement therapy for hypophosphatasia is now on clinical trial.

Osteogensis imperfecta and role of nurse in management

Osteogenesis imperfecta (OI) is a rare but striking cause of bone fragility and fractures. It usually presents in children or young adults. Consider it in the differential diagnosis when a child presents with a history of recurrent fractures. Early detection can improve morbidity. Nurses, if have the knowledge of the disease, can protect the child in hospital and can educate parents appropriately how to take care the child.

New genes in bone development: what's new in osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heritable bone dysplasia characterized by bone fragility and deformity and growth deficiency. Most cases of OI (classical types) have autosomal dominant inheritance and are caused by mutations in the type I collagen genes. During the past several years, a number of noncollagenous genes whose protein products interact with collagen have been identified as the cause(s) of rare forms of OI. This has led to a paradigm shift for OI as a collagen-related condition. The majority of the non-classical OI types have autosomal recessive inheritance and null mutations in their respective genes. The exception is a unique dominant defect in IFITM5, which encodes Bril and leads to hypertrophic callus and interosseous membrane ossification. Three recessive OI types arise from defects in any of the components of the collagen prolyl 3-hydroxylation complex (CRTAP, P3H1, CyPB), which modifies the collagen α1(I)Pro986 residue. Complex dysfunction leads to delayed folding of the procollagen triple helix and increased helical modification. Next, defects in collagen chaperones, HSP47 and FKBP65, lead to improper procollagen folding and deficient collagen cross-linking in matrix, respectively. A form of OI with a mineralization defect is caused by mutations in SERPINF1, whose protein product, PEDF, is a well-known antiangiogenesis factor. Defects in the C-propeptide cleavage enzyme, BMP1, also cause recessive OI. Additional genes, including SP7 and TMEM38B, have been implicated in recessive OI but are as yet unclassified. Elucidating the mechanistic pathways common to dominant and recessive OI may lead to novel therapeutic approaches to improve clinical manifestations.

Osteogenesis imperfecta

Osteogenesis imperfecta (OI), an inherited skeletal disorder characterized by low bone mass, bone fragility, and often short stature. The clinical severity varies widely from being nearly asymptomatic with a mild predisposition to fractures, normal stature and normal lifespan being to profoundly disabling and even lethal. Extra skeletal manifestations may include blue-grey sclera and dental abnormalities. Initially, the classification of OI into four types was based on clinical findings, but more recently additional types OI (types V-XI) have been ascertained, based on the identification of different mutations. While this classification is somewhat controversial, it is described in this article. The treatment of patients with OI is based on the nature and severity of symptoms. The goal of therapy is to prevent fractures and disability, improve function and quality of life. A multidisciplinary approach is needed, and treatment options include medication such as bisphosphonates, surgery, and rehabilitation. Investigations continue to explore gene and cell therapies that may be developed in the future.

Absence of FKBP10 in recessive type XI osteogenesis imperfecta leads to diminished collagen cross-linking and reduced collagen deposition in extracellular matrix

Recessive osteogenesis imperfecta (OI) is caused by defects in genes whose products interact with type I collagen for modification and/or folding. We identified a Palestinian pedigree with moderate and lethal forms of recessive OI caused by mutations in FKBP10 or PPIB, which encode endoplasmic reticulum resident chaperone/isomerases FKBP65 and CyPB, respectively. In one pedigree branch, both parents carry a deletion in PPIB (c.563_566delACAG), causing lethal type IX OI in their two children. In another branch, a child with moderate type XI OI has a homozygous FKBP10 mutation (c.1271_1272delCCinsA). Proband FKBP10 transcripts are 4% of control and FKBP65 protein is absent from proband cells. Proband collagen electrophoresis reveals slight band broadening, compatible with ≈10% over-modification. Normal chain incorporation, helix folding, and collagen T(m) support a minimal general collagen chaperone role for FKBP65. However, there is a dramatic decrease in collagen deposited in culture despite normal collagen secretion. Mass spectrometry reveals absence of hydroxylation of the collagen telopeptide lysine involved in cross-linking, suggesting that FKBP65 is required for lysyl hydroxylase activity or access to type I collagen telopeptide lysines, perhaps through its function as a peptidylprolyl isomerase. Proband collagen to organics ratio in matrix is approximately 30% of normal in Raman spectra. Immunofluorescence shows sparse, disorganized collagen fibrils in proband matrix.

[Osteogenesis imperfecta: clinical and genetic heterogeneity]

Osteogenesis imperfecta is a hereditary connective tissue disorder characterized primarily by fractures with no or small causal antecedent; in most patients this is a consequence of diminished or abnormal production of collagen type I. It is a clinically heterogeneous disorder: it has been proposed recently to classify osteogenesis imperfecta in types I-V on the basis of the clinical picture and radiology. It is also a genetically heterogeneous disorder; 90% of cases are due to autosomal dominant mutations, while the remaining 10% are due to autosomal recessive mutations or of unknown cause. Osteogenesis imperfecta type I and to a lesser extent type IV are important differential diagnostic considerations in case of suspicion of non-accidental injury (NAI). When osteogenesis imperfecta is suspected, DNA analysis of the dominant COL1A1 and COL1A2 genes is currently the starting point for laboratory diagnosis unless there are strong indications for a recessive cause. Protein analysis based on skin biopsy remains indicated in specific cases.

Biochemical bone markers in the assessment and pamidronate treatment of children and adolescents with osteogenesis imperfecta

AIM

 To assess the role of biochemical bone markers in classification of children with osteogenesis imperfecta (OI), their possible association with vertebral compression fractures in milder forms of OI and their role in monitoring of intravenous pamidronate (APD) treatment.

METHODS

 Serum total alkaline phosphatase (ALP), bone ALP isoforms (in a subgroup), osteocalcin, type I procollagen carboxy-terminal propeptide, carboxy-terminal telopeptide of type I collagen, and urine deoxypyridinoline (DPD) were measured in a cross-sectional study of 130 untreated individuals, 0.25-20.9years (median 6.7), with OI types I, III and IV. Of those, sixty-nine were also assessed longitudinally during monthly APD treatment. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry.

RESULTS

 Significant differences in bone markers, however not sufficient for individual clinical use, were found in the larger untreated group but not between subgroups with or without vertebral compressions. All bone markers decreased during treatment for 1.0-12.5years, but with different relative amounts. Changes were not correlated to the improvement in BMD, mobility or pain.

CONCLUSION

  Bone markers are, despite significant differences, not useful for the classification of OI type in the individual child and are not associated with vertebral compressions. Serum ALP and urinary DPD are sensitive in monitoring bisphosphonate treatment.

Bone mineral density and fracture rate in response to intravenous and oral bisphosphonates in adult osteogenesis imperfecta

The effect of bisphosphonate treatment on bone mineral density (BMD) and fracture rates was assessed in adults with osteogenesis imperfecta (OI). This observational nonrandomized study included 90 OI adults treated with intravenous pamidronate (n = 28), oral alendronate (n = 10), or oral residronate (n = 17) or not treated (n = 35). There were 63 type I, 15 type III, and 12 type IV OI patients. BMD results were observed for up to 161 months and an average of 52 months of treatment. For type I and grouped type III/IV patients, treatment with pamidronate showed an increasing rate in L1-L4 BMD from baseline (0.006 [P = 0.03] and 0.016 [P < 0.001] gm/cm(2)/year, respectively); oral bisphosphonate treatment showed a significant increasing rate in L1-L4 BMD (0.004 gm/cm(2)/year [P = 0.047]) for type I patients. Pamidronate-treated type III/IV and oral bisphosphonate-treated type I patients showed significant increases in total-hip BMD (0.006 [P = 0.003] and 0.011 [P = 0.046] gm/cm(2)/year, respectively). Bisphosphonate effect on fracture rate was assessed for 5-year periods before and after treatment in 51 treated and 22 nontreated individuals matched for age at which bisphosphonate was first administered to the treated group. Bisphosphonate treatment did not decrease fracture rate in type I OI patients. Fracture rate decreased in type III/IV patients following pamidronate but not following oral bisphosphonate treatment. These results underscore a need to consider whether bisphosphonate treatment is appropriate for all adults with OI.

[Genetic basis for skeletal disease. Osteogenesis imperfecta and genetic abnormalities]

Patients with osteogenesis imperfecta (OI) represent various degrees of bone fragility and accompany many clinical manifestations such as dentinogenesis imperfecta, blue sclera, growth disturbance, hearing impairment and so on. Although most OI is caused by genetic mutation of type I collagen gene ; COL1A1 and COL1A2, other genes that concerns post-translational modification of type I collagen molecules such as CRTAP, LEPRE1, PPIB, SERPINH1 and FKBP10 were found to be the causative candidates of OI. On the other hand, genetic causes of type V and type VI OI are not identified. For the classification of OI, Sillence's classification had been used and had been repeatedly revised at the times of identification of new causative genes of OI.

[Bone and joint diseases in children. Bisphosphonates in osteogenesis imperfecta]

Osteogenesis imperfecta (OI) is a genetic disorder characterized by fragile bone and reduced bone mineral density. Cyclic intravenous pamidronate is now the most widely used treatment for moderate to severe forms of OI. Oral bisphosphonates provide clinical benefit and convenience to the patients with mild form of OI. Recently, some studies demonstrated that intravenous zolendronate in children with OI is safe in short-term and similarly effective to parmidronate. Optimal dose, duration of treatment and long-term safety of newer bisphosphonates require further investigations.

[Biochemical markers of bone turnover. New aspect. Metabolic bone markers in osteogenesis imperfecta]

Osteogenesis imperfecta (OI) is a heterogeneous group of rare inherited bone and connective tissue disorders resulting from defect in collagen synthesis or function. It is characterized by bone fragility, which shows wide range of severities. The heterozygous mutations in the genes coding type I collagen are responsible to 80% of the OI cases. Metabolic bone markers relating type I collagen production or degraded products of mature collagen fiber may provides important information on the pathophysiology of OI. Typically, P1NP which is bone formation marker shows significant reduction and CTX or NTX shows relatively high level in type I OI. The other applications of metabolic bone markers in the management of OI will be discussed.

[Bisphosphonates and other new therapeutic agents for the treatmednt of osteogenesis imperfecta]

Osteogenesis imperfecta (OI) is a genetic disorder characterized by fragile bone and reduced bone mineral density. Cyclic intravenous pamidronate is now the standard treatment for moderate to severe forms of OI, however clinical studies are not yet sufficient to conclude appropriate annual doze and ideal duration of therapy at present time. Oral alendronate is also effective in milder forms of OI. Zoledronic acid has undergone international multicentric clinical trials to examine efficiency and long-term side effects including osteonecrosis of the jaw. Teriparatide (rhPTH1-34) and denosumab (monoclonal antibody against RANK ligand) have the potential for management of OI. Stem cell and gene therapy are currently being actively investigated and may become clinically applicable in the near future.

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.

Natural history of hyperplastic callus formation in osteogenesis imperfecta type V

Hyperplastic callus formation was assessed in 23 patients with osteogenesis imperfecta type V. Hyperplastic callus mostly affected long bones in the lower extremities and occurred predominantly during phases of rapid growth.

INTRODUCTION

Hyperplastic callus (HPC) formation is one of the most conspicuous features of osteogenesis imperfecta (OI) type V, but the natural history of HPC has not been well characterized.

MATERIALS AND METHODS

In this retrospective single-center study, we assessed HPC in 23 OI type V patients (9 females and 14 males).

RESULTS

Fifteen patients (65%) had HPC at 48 skeletal sites, 30 of which affected the lower limbs. The number of HPC sites per patient ranged from 0 to 7, with an average of 2.6 for men and 1.1 for women (p = 0.047 for this sex difference; t-test). New HPC formation was observed both after fractures and outside of the context of fractures. Only a minority of lower limb fractures (26%) precipitated HPC formation. After an initial enlargement phase, HPC lesions usually stabilized, but could also resolve completely (n = 2) or progress and lead to bone deformation. The most common complication of HPC was a fracture through the lesion (n = 7). Neither pamidronate nor indomethacin seemed to influence the course of HPC.

CONCLUSIONS

HPC is a potentially serious complication of OI type V. Given the rarity of the disorder, treatment studies will require multicenter collaborations.

Achondrogenesis

In this issue of Pediatric and Developmental Pathology, Aigner and colleagues report a detailed investigation of cartilage matrix changes in a 14-week fetus with achondrogenesis type IA. The changes reported differ from matrix alterations observed in achondrogenesis types IB or II and provide insight into the phenotypic and genotypic differences within this group of skeletal dysplasias.

Osteogenesis imperfecta

Osteogenesis imperfecta is a relatively common hereditary connective tissue disorder characterized by bone fragility and fractures. Other frequently affected tissues include tendons, ligaments, skin, sclera, teeth, and middle and inner ear. Molecular studies have demonstrated that most cases result from mutations affecting the genes responsible for the formation of type 1 collagen. The phenotypic presentation varies from mild to lethal. Commonly observed dental abnormalities include dentinogenesis imperfecta and malocclusion. Medical therapies using bisphosphonates have resulted in reduced fracture risk and decreased bone pain. To date, no cases of bisphosphonate-associated osteonecrosis have been reported. With appropriate precautions, the patient with osteogenesis imperfecta can tolerate and benefit from the delivery of necessary dental care to control oral disease, improve function, and improve esthetics.

[Genetic collagen disorders and the impact on craniofacial development]

Extracellular matrix molecules provide to tissues their mechanical properties and constitute a reservoir of local or regional signals that regulate cellular function. Collagens, the major components of osseous and collagenous matrices, have structural similarities, but are encoded by different genes. We describe here osteogenesis imperfecta, a collagen I, the principal constituent of bone, genetic disease, and its craniofacial implications. By comparing it with genetic disorders of cartilage collagen (Kniest and Stickler syndromes) we try to clarify the respective influences of these matrix molecules upon craniofacial development.

The effect of cyclical intravenous pamidronate in children and adolescents with osteogenesis imperfecta type V

Intravenous treatment with pamidronate is beneficial in children and adolescents with moderate to severe forms of osteogenesis imperfecta (OI) types I, III and IV, but there is little information on the effects of this treatment on the newly described OI type V. Here, we describe the results of 2 years of pamidronate treatment in 11 children and adolescents with OI type V (age at start of therapy 1.8 to 15.0 years; 6 girls). Pamidronate was given in intravenous cycles at a cumulative yearly dose of 9 mg/kg. The first infusion cycle was associated with fever and mild hypocalcemia in most patients, but no other short-term side effects were noted. Two years of pamidronate treatment led to a decrease in the urinary excretion of N-terminal telopeptide of type I collagen to 50% of baseline levels. Both the size and volumetric bone mineral density of lumbar vertebrae increased compared to age- and sex-matched reference data (P < 0.05 in both cases). Histomorphometry of transiliac bone samples showed an average increase of 86% in cortical thickness (N = 7; P = 0.005). No significant changes with treatment were observed in the age-related z scores of isometric maximal grip force and height. Fracture incidence decreased from 1.5 fractures per year before treatment to 0.5 fractures per year during the fist 2 years of treatment. Ambulation status improved in four patients and remained unchanged in the others. In conclusion, the intravenous pamidronate therapy has a similar effect in OI type V as it has in the other OI types.

[Idiopathic and secondary osteoporosis in childhood]

Osteoporosis is a common disease characterized by reduced bone mass, with a consequent increase in bone fragility and susceptibility to fracture risk. Bone mineral density (BMD) measurement is used to make the diagnosis of osteoporosis prior to incident fracture, and to predict fracture risk. BMD is determined by the peak bone mass achieved, and the rate and timing of subsequent bone loss. Dual-energy X-ray absorptiometry (DEXA) is the most popular and effective method utilized for osteoporosis screening. Bone disease is a side effect of concern regarding chronic glucocorticoid (GC) administration. Most GC-treated patients exhibit a process of bone loss, frequently leading to osteoporosis, with increased fracture risk, especially in spinal vertebrae. Osteogenesis imperfecta is an inherited and generalized connective tissue disorder characterized mainly by bone fragility. Idiopathic osteoporosis of childhood or adolescence without blue sclerae and other stigmata of osteogenesis imperfecta is occasionally observed and sometimes more than one sib is affected. Beta-thalassemia major is associated with significant bone disease. The etiology of the bone disease is still debatable, many factors can adversely affect bone accretion in thalassemic patients. These include delayed puberty, bone marrow expansion, the deleterious effects of desferrioxamine, iron overload and genetic factors. Current treatment alternatives of osteoporosis include bisphosphonates, calcitonin, and selective estrogen receptor modulators.

Avaliação clínica, radiográfica e laboratorial de pacientes com osteogênese imperfeita

BACKGROUND

Osteogenesis imperfecta is a genetic disorder characterized by defects in type I collagen. The main symptom is bone fragility and susceptibility to fractures. Other clinical findings are dentinogenesis imperfecta, blue sclera, early deafness and joint laxity. The purpose of this paper is to establish a practical relationship of the clinical differences between the Sillence's groups.

METHODS

22 patients were classified according to Sillence et al criteria and submitted to laboratory tests including blood calcium level and bone densitometry.

RESULTS

All clinical and laboratory differences were discussed in the text.

CONCLUSIONS

Differences such as results that were found in walking ability, height and bone densitometry were significant and may help to classify patients and to establish prognosis.

Cyclic bisphosphonate therapy in osteogenesis imperfecta type V

The clinical and radiographic features and management of a young person with recently delineated Osteogenesis Imperfecta Type V is described. A female aged 9 years presented with a history of multiple fractures since 3 years of age and bilateral dislocation of the elbows from infancy. She was commenced on a low dose frequent regimen of cyclic intravenous pamidronate, which resulted in progressive improvement in bone density, reduced fracture frequency and remission of symptoms of osteoporosis.

Craniofacial features in osteogenesis imperfecta: A cephalometric study

Osteogenesis imperfecta (OI) is a heterogeneous group of connective tissue diseases that mainly manifest as bone fragility and skeletal deformity. In most families it segregates as a dominant trait and results from mutations in type I collagen genes. In this study we analyzed the size and form of the bony structures in heads of 59 consecutive patients with OI types I, III, or IV (Sillence classification), using lateral radiographs. Paired controls were matched for gender and age. The purpose was to obtain baseline information of craniofacial development in OI patients that have not received bisphosphonate treatment. In OI type I we found smaller than normal linear measurements, indicating a general growth deficiency, but no remarkable craniofacial deformity. In OI types III and IV, the growth impairment was pronounced, and the craniofacial form was altered as a result of differential growth deficiency and bending of the skeletal head structures. We found strong support both for an abnormally ventral position of the sella region due to bending of the cranial base, and for a closing mandibular growth rotation. Vertical underdevelopment of the dentoalveolar structures and the condylar process were identified as the main reasons for the relative mandibular prognathism in OI. Despite of the widespread intervention with bisphosphonates, the facial growth impairment will probably remain characteristic for many OI patients, and their orthodontic treatment should be further developed.

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.

Intravenous pamidronate treatment of children under 36 months of age with osteogenesis imperfecta

INTRODUCTION

Bone mineral density (BMD) and fracture rates in children with osteogenesis imperfecta (OI) have been shown to improve with bisphosphonate therapy. There are limited data available on the efficacy of this therapy in children with OI under the age of 3 years. To examine this, we instituted a prospective clinical trial of intravenous bisphosphonate to study safety, feasibility, and efficacy of this therapy.

MATERIALS AND METHODS

Nine infants and young children with osteogenesis imperfecta (age range 1-35 months) were treated with intravenous pamidronate. Six had type II OI, two had type I, and one had type IV. Pamidronate was administered in cycles of 3 consecutive days. The total duration of therapy ranged from 11 to 29 months (mean 17 months).

RESULTS

During treatment, the mean annualized percent change in total body areal BMD was 25% (range 11-40%). Pamidronate therapy resulted in sustained and significant decreases in serum calcium and bone-specific alkaline phosphatase and in urine calcium/creatinine and NTX/creatinine. Fracture rate in the group decreased from 80 fractures in 111 months before treatment to 25 fractures in 152 months after treatment (P<0.01). Linear growth and weight gain were maintained. Other than fevers in several infants following the initial dose of intravenous bisphosphonate no adverse effects of therapy were noted.

CONCLUSIONS

Our data support that intravenous pamidronate therapy is safe, increases BMD, and reduces fracture rates in very young children with OI. Currently, it would seem to be the best available treatment for these children.

Syndromes with congenital brittle bones

Background

There is no clear definition of osteogenesis imperfecta (OI). The most widely used classification of OI divides the disease in four types, although it has been suggested that there may be at least 12 forms of OI. These forms have been named with numbers, eponyms or descriptive names. Some of these syndromes can actually be considered congenital forms of brittle bones resembling OI (SROI).

Discussion

A review of different syndromes with congenital brittle bones published in the literature is presented. Syndromes are classified in "OI" (those secondary to mutations in the type I pro-collagen genes), and "syndromes resembling OI" (those secondary to mutations other that the type I pro-collagen genes, identified or not). A definition for OI is proposed as a syndrome of congenital brittle bones secondary to mutations in the genes codifying for pro-collagen genes (COL1A1 and COL1A2).

Summary

A debate about the definition of OI and a possible clinical and prognostic classification are warranted.

[Lethal osteogenesis imperfecta. Prenatal diagnosis]

INTRODUCTION

Osteogenesis imparfecta (OI) comprises a group of disorders principally affecting type I collagen, which result in increased bone fragility. Lethal forms are rare and are characterised by micromelia with malformation of the limbs.

CASE REPORT

A prenatal diagnosis of lethal OI was made by ultrasonography at 18 weeks of gestation and therapeutic abortion was indicated.

COMMENTS

Molecular biology and genetic studies offer new possibilities of prenatal diagnosis, but ultrasonography remains the investigation of choice. It confirms the diagnosis by revealing an increase in bone transparency.

Osteogenesis imperfecta

Osteogenesis imperfecta is a genetic disorder of increased bone fragility, low bone mass, and other connective-tissue manifestations. The most frequently used classification outlines four clinical types, which we have expanded to seven distinct types. In most patients the disorder is caused by mutations in one of the two genes encoding collagen type 1, but in some individuals no such mutations are detectable. The most important therapeutic advance is the introduction of bisphosphonate treatment for moderate to severe forms of osteogenesis imperfecta. However, at present, the best treatment regimen and the long-term outcomes of bisphosphonate therapy are unknown. Although this treatment does not constitute a cure, it is an adjunct to physiotherapy, rehabilitation, and orthopaedic care. Gene-based therapy presently remains in the early stages of preclinical research.

Osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a rare congenital disorder of collagen production that results in brittle bones and affects other body systems containing collagen. This article reviews the current body of knowledge about OI and the management of infants with the disorder. Relieving pain, reducing the incidence of new fractures, establishing adequate follow-up, and connecting parents with community resources are the goals of management during the neonatal period. A case study illustrates management and the discharge process.

The interaction between Sillence type and BMD in osteogenesis imperfecta

Clinical studies with bisphosphonates in children with osteogenesis imperfecta (OI) show an increase in BMD and a decrease in fracture rate. Bone strength in children with OI is not only influenced by changes in BMD but also by changes in collagen I structure of the organic bone matrix. Therefore, we studied the interaction between these two factors in a cross-sectional, single center study including 54 children. We assumed that vertebral deformities in OI represent an unbalance between load and bone strength. Body weight was considered to be a well quantifiable load on vertebral bodies. BMD served as a marker, representing the amount of bone tissue available for vertebral load bearing, and the Sillence classification, either type I or III/IV, as a marker representing the quality of the organic bone matrix. Independent associations were observed between the prevalence of vertebral deformities and (1) Sillence type (OR: 5.7, 95%Cl:1.2-26.8), (2) BMD (OR: 0.003, 95%Cl: 0-0.25) and (3) body weight (OR: 1.15, 95%Cl: 1.05-1.25). Regarding the anthropometrical differences among the different types of OI, the BMD/body weight ratio was introduced to evaluate the BMD in relation to body size. Prevalent vertebral deformities were associated with low BMD/body weight ratios (OR: 0.04, 95%Cl: 0.008-0.2) in OI type I, but no association was found in type III/IV. It was concluded that BMD and Sillence type have independent relationships with vertebral deformities. The BMD/body weight ratio correlates with vertebral deformities in children with OI type I. Its meaning in types III/IV needs further research with larger samples because of the relatively high prevalence of vertebral deformities in this group.

[Updates in osteogenesis imperfecta]

Osteogenesis Imperfecta, a heterogenous group of inherited disorders, is characterized by both bone fragility and low bone mass. Since the Sillence classification of the disease, significant progress has been made in understanding the molecular, histological and genetical pathogenesis of the disease, and it led to expanded nosology. The multidisciplinary approach including rehabilitation, medications and surgery, may significantly improve the quality of life and prolong life expectancy.

Hypercalciuria in Osteogenesis Imperfecta Type I

BACKGROUND

In Osteogenesis Imperfecta severity of disease and reduced physical activity have been considered the main factors contributing to hypercalciuria; however, its pathogenesis in Osteogenesis Imperfecta Type I, in which mobility is normal, is still unclear.

PATIENT, METHODS AND RESULTS

We describe a patient with Osteogenesis Imperfecta Type I and hypercalciuria, in whom measurement of calcium intake, plasma 1 - 25(OH) (2) Vitamin D, fasting calciuria and tubular proteinuria led us to exclude an absorptive or renal component in the pathogenesis of hypercalciuria.

CONCLUSIONS

We believe that hypercalciuria is determined by bone disease in Osteogenesis Imperfecta Type I. This condition should be added to the causes of normocalcemic hypercalciuria in children and the mildest forms should be differentiated from Idiopathic Hypercalciuria.

Osteogenesis imperfecta--clinical and molecular diversity

Osteogenesis imperfecta is a heritable disorder of bone formation resulting in low bone mass and a propensity to fracture. It exhibits a broad range of clinical severity, ranging from multiple fracturing in utero and perinatal death to normal adult stature and a low fracture incidence. The disorder is currently classified into seven types based on differences in clinical presentation and bone architecture. Mutation in one of the type I collagen genes is commonly associated with osteogenesis imperfecta, but is not a prerequisite for the diagnosis. Indeed, the newer forms of osteogenesis imperfecta (types V, VI and VII) are not associated with type I collagen gene defects. Amongst the type I collagen gene mutations that can occur, missense base substitutions involving glycine codons in the exons encoding the central triple-helix forming domain predominate. Such mutations can occur in all the classical forms of osteogenesis imperfecta (types I-IV), but genotype/phenotype correlations are complex and often unpredictable. Treatment of osteogenesis imperfecta by bisphosphonate therapy can improve bone mass in all types of the disorder, and while not being a cure for the disorder does improve the quality of life of the patient.

Assessment of dysplastic dentin in osteogenesis imperfecta and dentinogenesis imperfecta

Two semiquantitative scoring systems, Clinical Radiographic Score (CRS) and Dysplastic Dentin Score (DDS), were introduced for analyzing degree of dysplastic manifestations in dentin. The utility of both systems was demonstrated in a large material of teeth from patients with dentinogenesis imperfecta (DI) and osteogenesis imperfecta (OI). Twenty teeth from healthy controls, 81 teeth from 40 patients with OI, and 18 teeth with DI without OI (DI type II) were examined. The degree of dysplasia was correlated with type and form of OI and type of DI. The median DDS did not differ between DI associated with OI (DI type I) and DI type II. DDS in OI patients without clinical signs of DI was above that of control teeth. Both circumpulpal and mantle dentin showed increased DDS, although circumpulpal dentin was more severely affected. The median DDS was highest for the most severe type of non-lethal OI (type III). DDS increased significantly with form (severity) of OI. A significant association between DDS and CRS was found, although diagnosis of DI in less severe cases was not possible based on radiographic or clinical signs alone. Thus, the DDS system proved valuable when the CRS system based on radiographic/clinical manifestations failed, the most significant finding being subclinical histological manifestations of DI in patients with OI but without clinical or radiographic signs of DI. These subtle dysplastic changes are most likely an expression of genetic disturbances associated with OI and should not be diagnosed as DI, but rather be termed histologic manifestations of dysplastic dentin associated with OI.

Significance of histopathologic examination in the diagnosis of dentin defects associated with type IV osteogenesis imperfecta: two case reports

Two cases of type IV osteogenesis imperfecta, which is divided into subtypes A and B on the basis of the absence or the presence of dental alterations, respectively, are examined with respect to their dental features clinically, radiographically, and histopathologically. There were no characteristic dental abnormalities noted on the clinical and radiographic examination. However, the histopathologic examination with both light and electron microscopy disclosed characteristic dentin defects such as unevenly calcified matrixes, irregular tubular patterns, obliterated dentinal tubules, and cellular inclusions in the circumpulpal dentin of primary teeth. As a result, the patients were diagnosed as having osteogenesis imperfecta type IVB, although the clinical dental alterations were scarcely apparent. These findings indicate the importance of histopathologic examination with light and transmission electron microscopy for accurate diagnosis of osteogenesis imperfecta.

New uses of bisphosphonates: osteogenesis imperfecta

Osteogenesis imperfecta is a heterogeneous group of inherited disorders chiefly affecting type I collagen, resulting in bone fragility responsible for a host of recurrent fractures. Limb and spine deformities, growth failure and restricted mobility are the end-result in severe cases. Cyclical intermittent intravenous infusions of pamidronate, a potent inhibitor of bone resorption, have yielded substantial improvement in chronic pain, bone mineral density, fracture rate and mobility without significant side effects. The role of growth hormone and bone marrow transplantation in the treatment of osteogenesis imperfecta is still unresolved. Newer, theoretically more potent bisphosphonates are currently being tested in this potentially crippling condition.