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.

[Update on prenatal diagnosis of osteogenesis imperfecta type II : an index case report diagnosed by ultrasonography in the first trimester]

INTRODUCTION

A case of osteogenesis imperfecta type II diagnosed in the first trimester of pregnancy.

DISCUSSION

Lethal osteogenesis imperfecta is a disorder characterized by collagen abnormalities resulting in dwarfism, bone fragility and deformity leading to death in utero or in the perinatal period. Molecular and biochemical studies demonstrate that OI type II results from mutations in either COL1 A1 or COL1 A2 which encode for the chains of type I procollagen. Early diagnosis by US examination in first trimester relies on shortening and bowing of long bones, multiple fractures and hypoechogenicity of the skeleton. When ultrasound examination suspects OI type II, the diagnosis can be accomplished in the first trimester by biochemical analysis if the collagen defect is characterized.

CONCLUSION

OI type II results mainly from private mutations and parental mosaicism is an important cause of recurrence making genetic counselling difficult.

[Valvular heart surgery in osteogenesis imperfecta]

Osteogenesis imperfecta is a disease in which fragile bones readily cause fracture. Valvular disease concurrently develops. However, the surgery-related mortality rate is approximately 30%. In this study, we report 2 patients with osteogenesis imperfecta who underwent valvular heart surgery. Patient 1 was a 31-year-old male. He had previously been diagnosed as having osteogenesis imperfecta. Echocardiography suggested aortic valve insufficiency, and aortic valve replacement was performed. Patient 2 was a 59-year-old male. During admission, osteogenesis imperfecta was diagnosed. Echocardiography suggested mitral valve insufficiency, and mitral valve plasty was performed. In the 2 patients, intraoperative hemorrhage was marked. However, there were no fatal complications. We also reviewed the literature.

Hearing loss in Finnish adults with osteogenesis imperfecta: a nationwide survey

Hearing loss, bone fragility, and blue sclerae are the principal clinical features in osteogenesis imperfecta (OI), a genetic disorder of connective tissue. In a nationwide search, an audiometric evaluation of 133 adult patients was performed. According to the criteria introduced by Sillence, type I was the most common form of OI. Of the patients with normal hearing on audiometry, 17.1% reported subjective hearing loss, and 19.1% of the patients with impaired hearing did not recognize it. On audiometry, 57.9% of the patients had hearing loss, which was progressive, often of mixed type, and mostly bilateral, and began in the second to fourth decades of life. The frequency or severity of the hearing loss was not correlated with any other clinical features of OI. Hearing loss is common, affecting patients with all types of OI. Subjective misjudgment of hearing ability supports the need for repeated audiometry in all OI patients. A baseline study at the age of OI years followed by audiograms every third year thereafter is recommended.

Advances in osteogenesis imperfecta

Considerable progress has been made in many aspects of osteogenesis imperfecta. The international Sillence classification of osteogenesis imperfecta is being expanded to include a greater range of subgroups of patients. Attempts are being made to identify the genes causing forms of osteogenesis imperfecta and related syndromes that are not caused by mutations of the Type I collagen genes. In medium-term studies, bisphosphonate treatment has been shown to be the first method of treatment to improve the clinical course of the disease significantly. Somatic cell therapy, using allogeneic bone marrow and mesenchymal stromal cell transplantation, are in their early phases of development for use in humans with osteogenesis imperfecta. Somatic gene therapy, which aims to inactivate the mutation, is being evaluated in laboratory and animal studies.

Musculo-skeletal problems associated with pregnancy in women with osteogenesis imperfecta

Having seen a number of women with osteogenesis imperfecta who developed severe back pain during or just after pregnancy, we wished to determine the likelihood of this and other musculoskeletal problems in pregnancy. We interviewed by telephone 100 women with osteogenesis imperfecta who had, between them, 213 pregnancies between 1957 and 1998. For each pregnancy we recorded the Sillence type for the osteogenesis imperfecta, the mode of delivery and the musculo-skeletal complications. The most common problem was back pain, which was severe in or after 28 pregnancies (13.1%). There was no identifiable relationship to the type of osteogenesis imperfecta or to the mode of delivery. In many cases the back pain could be related to crush fractures of vertebrae. Other problems identified included spinal deformity, non-vertebral fractures, disc problems and ligament problems. We suggest that it may be appropriate to advise the avoidance of long periods of breast feeding in women with OI, particularly in those who have vertebral fractures.

Dental aberrations in children and adolescents with osteogenesis imperfecta

The aim of this investigation was to study dental aberrations in a large sample of unrelated patients with different types and forms of osteogenesis imperfecta (OI). Sixty-eight non-related index patients aged 0.3 to 20 years (mean, 10 years) were examined clinically. Panoramic radiographs from 49 patients were analyzed. Dentinogenesis imperfecta (DI) type I was found in 27 of 65 patients and was significantly more common in OI type III than in types I and IV and in patients with a severe form of the disease. The presence or absence of DI showed almost complete accordance between affected parents and children and between affected siblings. Moreover, agenesis was found in 11 of 49 patients, apically extended pulp chambers in 20 of 48 patients, and impaction of second permanent molars in 7 of 19 patients older than 15 years. The percentage of patients with no apparent dental aberrations was approximately the same in patients with OI type I and type III and in patients with mild and severe form of the disease. The high prevalence of dental aberrations in OI stresses the importance of clinical and radiographic odontologic examination as part of the clinical investigation. In patients with mild forms of the disease, in whom the medical diagnosis is uncertain, demonstration of disturbances in dental development can be crucial for establishing the OI diagnosis. C

Osteogenesis imperfecta type VI: a form of brittle bone disease with a mineralization defect

Osteogenesis imperfecta (OI) is a heritable disease of bone in which the hallmark is bone fragility. Usually, the disorder is divided into four groups on clinical grounds. We previously described a group of patients initially classified with OI type IV who had a discrete phenotype including hyperplastic callus formation without evidence of mutations in type I collagen. We called that disease entity OI type V. In this study, we describe another group of 8 patients initially diagnosed with OI type IV who share unique, common characteristics. We propose to name this disorder "OI type VI." Fractures were first documented between 4 and 18 months of age. Patients with OI type VI sustained more frequent fractures than patients with OI type IV. Sclerae were white or faintly blue and dentinogenesis imperfecta was uniformly absent. All patients had vertebral compression fractures. No patients showed radiological signs of rickets. Lumbar spine areal bone mineral density (aBMD) was low and similar to age-matched patients with OI type IV. Serum alkaline phosphatase levels were elevated compared with age-matched patients with type IV OI (409 +/- 145 U/liter vs. 295 +/- 95 U/liter; p < 0.03 by t-test). Other biochemical parameters of bone and mineral metabolism were within the reference range. Mutation screening of the coding regions and exon/intron boundaries of both collagen type I genes did not reveal any mutations, and type I collagen protein analyses were normal. Qualitative histology of iliac crest bone biopsy specimens showed an absence of the birefringent pattern of normal lamellar bone under polarized light, often with a "fish-scale" pattern. Quantitative histomorphometry revealed thin cortices, hyperosteoidosis, and a prolonged mineralization lag time in the presence of a decreased mineral apposition rate. We conclude that type VI OI is a moderate to severe form of brittle bone disease with accumulation of osteoid due to a mineralization defect, in the absence of a disturbance of mineral metabolism. The underlying genetic defect remains to be elucidated.

Osteogenesis imperfecta at the beginning of bone and joint decade

Osteogenesis imperfecta (OI), or brittle bone disease, is a heritable disorder characterized by increased bone fragility. Four different types of the disease are commonly distinguished, ranging from a mild condition (type I) to a lethal one (type II). Types III and IV are the severe forms surviving the neonatal period. In most cases, there is a reduction in the production of normal type I collagen or the synthesis of abnormal collagen as a result of mutations in the type I collagen genes. These classic forms of OI are described in this review. There are instances, however, where alterations in bone matrix components, other than type I collagen, are the basic abnormalities of the OI. Recently, three such discrete types have been identified by histomorphometric evaluation (types V and VI) and linkage analysis (Rhizomelic OI). They provide evidence for the as yet poorly understood complexity of the phenotype-genotype correlation in OI. We also discuss bisphosphonates treatment as well as fracture management and surgical correction of deformities observed in the patients with OI. However, ultimately, strengthening bone in OI will involve steps to correct the underlying genetic mutations that are responsible for this disorder. Thus, we also describe different genetic therapeutic approaches that have been tested either on OI cells or on available OI murine models.

[Prenatal and neonatal diagnosis of osteogenesis imperfecta in obstetrical practice]

Osteogenesis imperfecta (OI types I, II, III, IV) is a heterogeneous group of genetically disorders of connective tissue. Quantitative or qualitative abnormalities of type I collagen form pathogenetical basis of the disease. They are caused by mutations in genes encoding collagen proteins or enzymes involved in collagen biosynthesis. The clinical features of each type usually correspond to the type of mutation. Typical manifestations are fragile bones with multiple bone fractures and bone deformities. Currently applied diagnosis in utero of OI II and sometimes OI III may be performed. Diagnosis of other OI phenotypes cannot be made until after birth. We present three cases of OI II (four children) diagnosed, in utero, by ultrasound examination. The analysis in work include: 1. the prenatal sonographic features of OI type II 2. the biochemical properties of collagen in the above cases 3. genetic counselling of the families affected by OI.

Thirty-three novel COL1A1 and COL1A2 mutations in patients with osteogenesis imperfecta types I-IV

Osteogenesis imperfecta (OI) is a heritable disease of bone characterized by low bone mass and bone fragility. Six different types of OI have been described to date, based on clinical phenotype and histological findings. The genetic defect in many patients with OI types I-IV is due to mutations in the genes encoding type I collagen, while patients with OI types V and VI show no evidence of mutations in the COL1A1/COL1A2 genes. Here we report thirty-three novel mutations in patients with types I-IV OI. Sixteen mutations were in COL1A1 and seventeen were in COL1A2. Most mutations resulted in substitutions for glycine: one of these, a doublet GG>CC transversion, created a unique Gly-->Pro missense mutation in the triple helical domain of COL1A2. Two rare triple helical Gly-->Glu substitutions in COL1A2 are also described. In addition, there were six single-base deletion mutations resulting in frameshifts, seven splice junction mutations, and a 9-bp triple helix insertion associated with a severe (OI II) phenotype. The variety of mutations described in the COL1A1/COL1A2 genes giving rise to an OI phenotype is in accordance with the clinical heterogeneity of the disease. Hum Mutat 17:434, 2001.

[Osteogenesis imperfecta: a new, early therapeutic approach with biphosphonates. A case report]

Management of type III osteogenesis imperfecta (O.I.) (brittle bone disease) is primarily supportive; early introduction of cyclic intravenous pamidronate administration in children younger than 2 years of age is an innovative and promising therapeutic approach.

CASE REPORT

We present the case of a 6-month-old infant, whose preliminary data have already been partly published, with severe type III O.I. referred because of aching and crumbling from multiple fractures. Cyclic intravenous disodic pamidronate administration improved the clinical status (fracture incidence, pain, growth curve) and biological status (bone density, osseous alkaline phosphatases, urinary desoxypiridoline excretion), allowing a remarkable recovery.

CONCLUSION

Biphosphonates are a new and innovative therapeutic agent in O.I. Clinical safety, easy administration, and overall efficacy are likely to extend their use in severe type III O.I. from the very first months of life, the time of best efficacy.

Osteogenesis imperfecta and other skeletal dysplasias presenting with increased nuchal translucency in the first trimester

We present two case reports of osteogenesis imperfecta associated with increased nuchal translucency in the first trimester. We also review the literature of first trimester diagnosis of skeletal dysplasias and their association with increased nuchal translucency.

A light and electron microscopic study of osteogenesis imperfecta bone samples, with reference to collagen chemistry and clinical phenotype

A detailed morphological study was carried out using light and electron microscopy on 36 bone specimens from patients suffering from osteogenesis imperfecta (OI) and 20 age- and site-matched control bone specimens. The findings were grouped into the clinical types of OI according to the Sillence classification. The morphological and ultrastructural alterations observed in OI bone correlate well with clinical severity. Thus, OI type I, the mildest type, showed the least abnormalities in bone ultrastructure. OI type IV closely resembled type I, with only minor abnormalities in the bone cells and osteoid. OI type III showed abnormalities in the structure and distribution of osteoid collagen fibrils, whilst OI type II, the lethal form, revealed many varied abnormalities such as thin cortical bone, sparse trabecular bone, increased numbers of osteoclasts and osteocytes, thin osteoid with thin collagen fibrils, and patchy mineralization.

Osteogenesis imperfecta: practical treatment guidelines

Osteogenesis imperfecta (OI), an inherited connective tissue disorder of remarkable clinical variability, is caused by a quantitative or qualitative defect in collagen synthesis and is characterised by bone fragility. The number of fractures and deformities, and the age at which they begin greatly influence the prognosis and the achievement of walking and autonomy. A multidisciplinary team approach is essential for diagnosis, for communication with patient and parents, and to tailor treatment needs to the severity of the disease and the age of the patient. Three types of treatment are available: nonsurgical management (physical therapy, rehabilitation, bracing and splinting), surgery (intramedullary rod positioning, spinal and basilar impression surgery), and drugs to increase the strength of bone and decrease the number of fractures. An aggressive rehabilitative approach is indicated to optimise functional ability and walking capacity; appropriately timed surgery to insert intramedullary rods provides improved function of extremities. Despite a high rate of complications, intramedullary telescopic roding has proven to be the most successful method for preventing and correcting fractures and deformities of long bones, improving walking capability and leading to successful rehabilitation of even severely affected patients. Surgery may be required in patients with progressive spinal deformity and in those with symptomatic basilar impression. Hearing function, dentinogenesis imperfecta, cardiac and respiratory function, and neurological changes must be monitored. The causal defect of the disease cannot be corrected with medical treatment and, currently, only symptomatic therapy is available. In recent years growth hormone (GH) and bisphosphonate agents have been used in OI therapy. GH is beneficial in patients with moderate forms of OI, showing a positive effect on bone turnover, bone mineral density and height velocity rate. Bisphosphonates have proved beneficial in children with severe OI, increasing bone mineral density and reducing the fracture rate and pain with no adverse effects reported. These data require confirmation in double-blind controlled studies; however, bisphosphonates have markedly improved morbidity in patients with OI. Future developments in genetic therapy may be directed towards either replacing cells carrying the mutant gene with normal cells or silencing the mutant allele using antisense suppression therapy, thus transforming a biochemically severe form of OI into a mild form.

Type V osteogenesis imperfecta: a new form of brittle bone disease

Osteogenesis imperfecta (OI) is commonly subdivided into four clinical types. Among these, OI type IV clearly represents a heterogeneous group of disorders. Here we describe 7 OI patients (3 girls), who would typically be classified as having OI type IV but who can be distinguished from other type IV patients. We propose to call this disease entity OI type V. These children had a history of moderate to severe increased fragility of long bones and vertebral bodies. Four patients had experienced at least one episode of hyperplastic callus formation. The family history was positive for OI in 3 patients, with an autosomal dominant pattern of inheritance. All type V patients had limitations in the range of pronation/supination in one or both forearms, associated with a radiologically apparent calcification of the interosseous membrane. Three patients had anterior dislocation of the radial head. A radiodense metaphyseal band immediately adjacent to the growth plate was a constant feature in growing patients. Lumbar spine bone mineral density was low and similar to age-matched patients with OI type IV. None of the type V patients presented blue sclerae or dentinogenesis imperfecta, but ligamentous laxity was similar to that in patients with OI type IV. Levels of biochemical markers of bone metabolism generally were within the reference range, but serum alkaline phosphatase and urinary collagen type I N-telopeptide excretion increased markedly during periods of active hyperplastic callus formation. Qualitative histology of iliac biopsy specimens showed that lamellae were arranged in an irregular fashion or had a meshlike appearance. Quantitative histomorphometry revealed decreased amounts of cortical and cancellous bone, like in OI type IV. However, in contrast to OI type IV, parameters that reflect remodeling activation on cancellous bone were mostly normal in OI type V, while parameters reflecting bone formation processes in individual remodeling sites were clearly decreased. Mutation screening of the coding regions and exon/intron boundaries of both collagen type I genes did not reveal any mutations affecting glycine codons or splice sites. In conclusion, OI type V is a new form of autosomal dominant OI, which does not appear to be associated with collagen type I mutations. The genetic defect underlying this disease remains to be elucidated.

Osteogenesis imperfecta in childhood: prognosis for walking

OBJECTIVES

We studied the predicted value of disease-related characteristics for the ability of children with osteogenesis imperfecta (OI) to walk.

STUDY DESIGN

The severity of OI was classified according to Sillence. The parents were asked to report the age at which the child achieved motor milestones, the fracture incidence, and the age and localization of the first surgical intervention. The present main means of mobility was classified according to Bleck.

RESULTS

There were 76 replies to the 98 questionnaires, of which 70 were included (type I, 41; type III, 11; type IV, 18). The type of OI was strongly associated with current walking ability, as was the presence of dentinogenesis imperfecta. Patients with type III and IV had a lower chance of ultimately walking compared with those with type I. Children with more than 2 intramedullary rods in the lower extremities had a reduced chance of walking than patients without rods. Rolling over before 8 months, unsupported sitting before 9 months, the ability to get in sitting position without support before 12 months, and the ability to get in a standing position without support before 12 months showed positive odds ratios. In Bleck > or = 4, multivariate analysis revealed that only the presence of rodding (yes/no) in the lower extremities had additional predictive value to the type of OI. The presence of dentinogenesis imperfecta and rodding (yes/no) had additional value in Bleck > or = 5.

CONCLUSION

The type of OI is the single most important clinical indicator of the ultimate ability to walk. Information about motor development adds little. The early achievement of motor milestones contributes to the ability of independent walking when the type of OI is uncertain. Intramedullary rodding of the lower extremities is primarily related to the severity of the disease and in this way provides consequences for the ability to walk.

Skewfoot in patients with osteogenesis imperfecta

We report skewfoot deformities in two patients who have osteogenesis imperfecta. A discussion will follow proposing etiologies of skewfoot, speculating that the ligamentous laxity often present in children who have osteogenesis imperfecta may predispose the development of skewfoot.

Osteogenesis imperfecta: profiles of motor development as assessed by a postal questionnaire

This study was performed to achieve more detailed information regarding the age and sequence in the development of motor milestones in the different types of osteogenesis imperfecta (OI). The parents of 98 patients with a diagnosis of OI were sent a questionnaire regarding the age at which patients achieved motor milestones. All patients were attending the outpatient clinic for children with OI at the Wilhelmina Children's Hospital. The motor milestones were classified into static motor milestones and dynamic motor milestones and all data were checked with health care records. The age of development of motor milestones was compared to reference values of the healthy population. The severity of the disease was classified according to Sillence based on clinical, genetic and radiological data. The age of intramedullary rodding of the first nail in the lower and upper extremity and the localisation was noted. A total of 76 parents responded to the 98 questionnaires (78%). In OI type I, a delay exists in achieving motor milestones, comparable to the 95th percentile of the normal population. In type III, the development of all motor milestones was significantly delayed compared to types I and IV with a discrepancy between static and dynamic milestones. In OI type IV, a retardation in motor development developed after the milestone 'sitting without support' was achieved. Motor development in types I and IV was not influenced by intramedullary rodding of the lower extremities, since rodding was rarely performed before the milestone 'unsupported standing' was achieved. In type III, the influence of intramedullary rodding on the age of achieving motor milestones remains questionable.

CONCLUSION

The severity of osteogenesis imperfecta has a large influence on the age and sequence in the development of motor milestones. No influence of intramedullary rodding of the lower extremities on motor development was found in osteogenesis imperfecta types I and IV, whereas the influence in type III remains questionable.

Pyridinium cross-links in bone of patients with osteogenesis imperfecta: evidence of a normal intrafibrillar collagen packing

The brittleness of bone in patients with osteogenesis imperfecta (OI) has been attributed to an aberrant collagen network. However, the role of collagen in the loss of tissue integrity has not been well established. To gain an insight into the biochemistry and structure of the collagen network, the cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) and the level of triple helical hydroxylysine (Hyl) were determined in bone of OI patients (types I, III, and IV) as well as controls. The amount of triple helical Hyl was increased in all patients. LP levels in OI were not significantly different; in contrast, the amount of HP (and as a consequence the HP/LP ratio and the total pyridinoline level) was significantly increased. There was no relationship between the sum of pyridinolines and the amount of triple helical Hyl, indicating that lysyl hydroxylation of the triple helix and the telopeptides are under separate control. Cross-linking is the result of a specific three-dimensional arrangement of collagens within the fibril; only molecules that are correctly aligned are able to form cross-links. Inasmuch as the total amount of pyridinoline cross-links in OI bone is similar to control bone, the packing geometry of intrafibrillar collagen molecules is not disturbed in OI. Consequently, the brittleness of bone is not caused by a disorganized intrafibrillar collagen packing and/or loss of cross-links. This is an unexpected finding, because mutant collagen molecules with a random distribution within the fibril are expected to result in disruptions of the alignment of neighboring collagen molecules. Pepsin digestion of OI bone revealed that collagen located at the surface of the fibril had lower cross-link levels compared with collagen located at the inside of the fibril, indicating that mutant molecules are not distributed randomly within the fibril but are located preferentially at the surface of the fibril.

Hearing loss in children with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue. Progressive hearing loss is one of the principal symptoms of OI, affecting about 50% of adult patients. Hearing loss may also occur in childhood and results in additional disability in education and psychosocial adaptation and aggravates the physical handicap. This can be avoided by appropriate otological and audiological treatment. In a nationwide search, 254 Finnish patients with OI were identified indicating a prevalence of 4.9/100,000. Of the 60 children, 45 aged between 4 and 16 years accepting to participate the study on hearing, were evaluated by a questionnaire and clinical audiometry. Hearing loss was defined as pure tone average (PTA0.5-2 kHz) more than 20 dB hearing level (HL). A clinical geneticist determined the type of OI among the 45 patients. Two sporadic OI cases with conductive hearing loss were ascertained (4.4%): An 11-year-old girl with type IV OI with a PTA0.5-2 kHz of 35/40 dB HL and a 15-year-old boy with type IV OI with a PTA0.5-2 kHz of 27/18 dB HL. In addition, a 6-year-old girl with familial OI type I had either a congenital sensorineural deafness or early progressive deafness with PTA0.5-2 kHz of 97/103 dB HL, probably of unrelated aetiology.

CONCLUSION

Hearing loss in children with osteogenesis imperfecta is less frequent than generally suspected. Nevertheless, it is recommended that audiometry is performed in children with osteogenesis imperfecta even without symptoms of hearing loss at the age of 10 years, and repeated every 3 years thereafter.