Efficacy of teriparatide vs neridronate in adults with osteogenesis imperfecta type I: a prospective randomized international clinical study

Osteogenesis imperfecta type V: About a clinical case

Osteogenesis imperfecta (OI) is a rare inherited connective tissue disorder. It is characterized by short stature, fragility and decreased bone mass, which leads to multiple and recurrent fractures after low-energy trauma, which generates susceptibility to long bone deformity and vertebral compression. There are several types of OI, with types I to IV, in which the COL1A1 and COL1A2 genes are affected, being the most frequent. In recent years, the discovery of new forms of OI has led to research into the pathways critical aspects of bone metabolism, with new genes involved being identified. The mutation in IFITM5 has been identified as the cause of OI type V, of autosomal dominant inheritance. OI type V has distinctive clinical features including the development of hypertrophic callus after fracture, early calcification of the interosseous membrane in the forearm, and the presence of hyperdense metaphyseal bands. The case of a patient with a novo mutation in IFITM5 is presented.

Osteogenesis imperfecta: shifting paradigms in pathophysiology and care in children

The formation of functional bone requires a delicate interplay between osteogenesis and osteolysis. Disturbances in this subtle balance result in an increased risk for fractures. Besides its mechanical function, bone tissue represents a key player in the regulation of calcium homeostasis. Impaired bone formation results in bone fragility, which is especially pronounced in osteogenesis imperfecta (OI). This rare genetic disorder is characterized by frequent fractures as well as extraskeletal manifestations. The current classification of OI includes 23 distinct types. In recent years, several new mutations in different genes have been identified, although the exact pathomechanisms leading to the clinical presentation of OI often remain unclear. While bisphosphonates are still the standard of care, novel therapeutic approaches are emerging. Especially, targeted antibody therapies, originally developed for osteoporosis, are increasingly being investigated in children with OI and represent a promising approach to alleviate the consequences of impaired osteogenesis and improve quality of life in OI patients. This review aims to provide insight into the pathophysiology of OI and the consequences of distinct disease-causing mutations affecting the regulation of bone homeostasis. In this context, we describe the four most recently identified OI-causing genes and provide an update on current approaches for diagnosis and treatment.

Efficacy of Recombinant Human Parathyroid Hormone 1-34 and Vitamin K2 Combination Therapy in Postmenopausal Osteoporosis

This study aimed to assess the efficacy and safety of a combined recombinant human parathyroid hormone 1-34 [rhPTH (1-34)] and vitamin K2 therapy versus vitamin K2 alone in the treatment of postmenopausal osteoporosis. A total of 77 postmenopausal osteoporosis patients were randomly divided into two groups. Patients in one group received vitamin K2 alone, while patients in the other group received a combination of rhPTH (1-34) and vitamin K2. Bone mineral density (BMD), electrolyte levels, pain scores, bone metabolism levels, and adverse drug reactions were compared pre- and post-treatment. Both two treatments improved BMD, blood calcium concentrations, pain scores, and increased osteocalcin and osteoprotegerin levels. Notably, the combined rhPTH (1-34) and vitamin K2 treatment demonstrated superior efficacy in improving BMD and bone metabolism markers. Furthermore, there was no significant difference in the incidence of adverse reactions between the two groups, indicating the safety of the combined treatment. In summary, the combined therapy of rhPTH (1-34) and vitamin K2 exhibited more potent efficacy in the treatment of postmenopausal osteoporosis, more effectively enhancing BMD and bone metabolism markers than vitamin K2 alone, without a significant increase in adverse reactions.

Current and Developing Pharmacologic Agents for Improving Skeletal Health in Adults with Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility largely caused by defects in structure, synthesis, or post-translational processing of type I collagen. Drugs currently used to improve skeletal health in OI were initially developed to treat osteoporosis and clinical trials are ongoing to study their effectiveness in OI adults. Additionally, novel bone-protective agents are in preclinical studies and various phases of OI clinical trials. This review summarizes current knowledge on available pharmacologic agents and current drug trials involving OI participants. A PubMed online database search of all study types published in the English language using the terms "osteogenesis imperfecta," "OI," and "brittle bone disease" was performed in August 2022. Articles screened were restricted to adults. A ClinicalTrials.gov database search of all studies involving "osteogenesis imperfecta" was performed in August 2023. Although clinical trial data are limited, bisphosphonates and teriparatide may be useful in improving bone mineral density. As of yet, no clinical trials are available that adequately evaluate the usefulness of current therapies in reducing fracture risk. Several therapeutics, including teriparatide, setrusumab, anti-TGF-β antibodies, and allogeneic stem cells, are being studied in clinical trials. Preclinical studies involving Dickkopf-1 antagonists present promising data in non-OI bone disease, and could be useful in OI. Research is ongoing to improve therapeutic options for adults with OI and clinical trials involving gene-editing may be possible in the coming decade.

Bone Metabolism, Bone Mass, and Bone Structure During Pregnancy and Lactation: Normal Physiology and Pregnancy and Lactation-Associated Osteoporosis

This article reviews bone metabolism, bone mass, and bone structure changes expected during and after pregnancy and lactation, as well as the condition of pregnancy and lactation-associated osteoporosis (PLO)-a presentation with fragility fracture(s) in the context of these physiologic changes. Clinical implications of physiologic bone changes will be addressed, as will specific management considerations that apply to premenopausal women with PLO.

Medication-related osteonecrosis of the jaw (MRONJ): a review of pathogenesis hypothesis and therapy strategies

Medication-related osteonecrosis of the jaw (MRONJ), a severe side effect caused by antiresorptive antiangiogenic medication, particularly bisphosphonates (BPs), has become a challenging disease with serious and profound effects on the physical and mental health of patients. Although it occurs with high frequency and is harmful, the exact mechanism of MRONJ remains unknown, and systematic and targeted approaches are still lacking. Maxillofacial surgeons focus on the etiology of osteonecrosis in the mandible and maxilla as well as the appropriate oral interventions for high-risk patients. Adequate nursing care and pharmacotherapy management are also crucial. This review provides a current overview of the clinicopathologic feature and research of MRONJ caused by BPs, with an emphasis on the potential mechanisms and current therapy and prevention strategies of the disease. We are of the opinion that an in-depth comprehension of the mechanisms underlying MRONJ will facilitate the development of more precise and efficacious therapeutic approaches, resulting in enhanced clinical outcomes for patients.

New Perspectives of Therapies in Osteogenesis Imperfecta-A Literature Review

(1) Background: Osteogenesis imperfecta (OI) is a rare skeletal dysplasia characterized as a heterogeneous disorder group with well-defined phenotypic and genetic features that share uncommon bone fragility. The current treatment options, medical and orthopedic, are limited and not efficient enough to improve the low bone density, bone fragility, growth, and mobility of the affected individuals, creating the need for alternative therapeutic agents. (2) Methods: We searched the medical database to find papers regarding treatments for OI other than conventional ones. We included 45 publications. (3) Results: In reviewing the literature, eight new potential therapies for OI were identified, proving promising results in cells and animal models or in human practice, but further research is still needed. Bone marrow transplantation is a promising therapy in mice, adults, and children, decreasing the fracture rate with a beneficial effect on structural bone proprieties. Anti-RANKL antibodies generated controversial results related to the therapy schedule, from no change in the fracture rate to improvement in the bone mineral density resorption markers and bone formation, but with adverse effects related to hypercalcemia. Sclerostin inhibitors in murine models demonstrated an increase in the bone formation rate and trabecular cortical bone mass, and a few human studies showed an increase in biomarkers and BMD and the downregulation of resorption markers. Recombinant human parathormone and TGF-β generated good results in human studies by increasing BMD, depending on the type of OI. Gene therapy, 4-phenylbutiric acid, and inhibition of eIF2α phosphatase enzymes have only been studied in cell cultures and animal models, with promising results. (4) Conclusions: This paper focuses on eight potential therapies for OI, but there is not yet enough data for a new, generally accepted treatment. Most of them showed promising results, but further research is needed, especially in the pediatric field.

Perspective: A multi-trait integrative approach to understanding the structural basis of bone fragility for pediatric conditions associated with abnormal bone development

Bone development is a highly orchestrated process that establishes the structural basis of bone strength during growth and functionality across the lifespan. This developmental process is generally robust in establishing mechanical function, being adaptable to many genetic and environmental factors. However, not all factors can be fully accommodated, leading to abnormal bone development and lower bone strength. This can give rise to early-onset bone fragility that negatively impacts bone strength across the lifespan. Current guidelines for assessing bone strength include measuring bone mineral density, but this does not capture the structural details responsible for whole bone strength in abnormally developing bones that would be needed to inform clinicians on how and when to treat to improve bone strength. The clinical consequence of not operationalizing how altered bone development informs decision making includes under-detection and missed opportunities for early intervention, as well as a false positive diagnosis of fragility with possible resultant clinical actions that may actually harm the growing skeleton. In this Perspective, we emphasize the need for a multi-trait, integrative approach to better understand the structural basis of bone growth for pediatric conditions with abnormal bone development. We provide evidence to showcase how this approach might reveal multiple, unique ways in which bone fragility develops across and within an array of pediatric conditions that are associated with abnormal bone development. This Perspective advocates for the development of new translational research aimed at informing better ways to optimize bone growth, prevent fragility fractures, and monitor and treat bone fragility based on the child's skeletal needs.

A New COL1A1 Mutation Associated With Type I Osteogenesis Imperfecta: Treatment Options for a Woman of Childbearing Age

Osteogenesis imperfecta (OI) is a rare heritable skeletal dysplasia, clinically characterized by abnormal bone fragility and predisposition to fractures. Here, we describe the case of a 30-year-old woman harboring a novel frameshift variant in the COL1A1 gene, causing a mild but characteristic phenotype of type I OI. She has blue sclerae, a medical history of fractures during infancy and puberty, a vertebral fracture at a young age, and joint hypermobility. The mutation, c.108del (p.Pro37GInfs*37), causes a premature stop codon insertion, predicted to lead to an unstable mRNA, with a consequent reduction in type I collagen quantity. At present, little is known about the evolution of this phenotype during pregnancy, lactation, and premenopause, conditions that could increase the risk of fractures. Management of type I OI in a young woman of childbearing potential is problematic because most antiosteoporotic drugs are contraindicated in pregnancy, as discussed in our brief review.

Approach to the Patient: Pharmacological Therapies for Fracture Risk Reduction in Adults With Osteogenesis Imperfecta

CONTEXT

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility largely caused by defects in structure, synthesis, or post-translational processing of type I collagen. The effectiveness of medications used for fracture reduction in adults with OI is understudied and practice recommendations are not well established. Drugs currently used to improve skeletal health in OI were initially developed to treat osteoporosis. Oral and intravenous bisphosphonates have been shown to improve bone mineral density (BMD) in adults with OI and are commonly used; however, conclusive data confirming fracture protection are lacking. Similarly, teriparatide appears to increase BMD, an effect that seems to be limited to individuals with type I OI. The role of denosumab, abaloparatide, romosozumab, and estradiol/testosterone in adult OI have not been systematically studied. Anti-sclerostin agents and transforming growth factor-beta antagonists are under investigation in clinical trials.

OBJECTIVE

This review summarizes current knowledge on pharmacologic treatment options for reducing fracture risk in adults with OI.

METHODS

A PubMed online database search of all study types published in the English language using the terms "osteogenesis imperfecta," "OI," and "brittle bone disease" was performed in June 2022. Articles screened were restricted to adults. Additional sources were identified through manual searches of reference lists.

CONCLUSION

Fracture rates are elevated in adults with OI. Although clinical trial data are limited, bisphosphonates and teriparatide may be useful in improving BMD. Further research is needed to develop medications for adults with OI that will lead to definite fracture rate reduction.

Murine Animal Models in Osteogenesis Imperfecta: The Quest for Improving the Quality of Life

Osteogenesis imperfecta is a rare genetic disorder characterized by bone fragility, due to alterations in the type I collagen molecule. It is a very heterogeneous disease, both genetically and phenotypically, with a high variability of clinical phenotypes, ranging from mild to severe forms, the most extreme cases being perinatal lethal. There is no curative treatment for OI, and so great efforts are being made in order to develop effective therapies. In these attempts, the in vivo preclinical studies are of paramount importance; therefore, serious analysis is required to choose the right murine OI model able to emulate as closely as possible the disease of the target OI population. In this review, we summarize the features of OI murine models that have been used for preclinical studies until today, together with recently developed new murine models. The bone parameters that are usually evaluated in order to determine the relevance of new developing therapies are exposed, and finally, current and innovative therapeutic strategies attempts considered in murine OI models, along with their mechanism of action, are reviewed. This review aims to summarize the in vivo studies developed in murine models available in the field of OI to date, in order to help the scientific community choose the most accurate OI murine model when developing new therapeutic strategies capable of improving the quality of life.

[Osteogenesis imperfecta : A multidisciplinary challenge]

Osteogenesis imperfecta (OI) describes a group of rare diseases which are associated with an increased tendency to bone fractures. In addition to the main symptom of fractures, OI is characterized by a variety of pediatric, pediatric orthopedic and anesthesiological challenges. The multidisciplinary expertise is mostly concentrated at specialized centers. The current treatment concepts aim at minimizing the fracture rate, prevention and treatment of deformities, pain reduction and improved mobility. In addition to pharmacotherapy, conservative and surgical measures are also applied. Scheduled interventions on the extremities are one of the most commonly performed operations in children with OI. Various intramedullary nailing techniques are available. This article addresses the important aspects of multidisciplinary care of children with OI concerning the treatment of the lower extremities.

Acetabular Revision Surgery with Tantalum Trabecular Metal Acetabular Cup for Failed Acetabular Cage Reconstruction with Bone Allografts: A Retrospective Study with Mid- to Long-Term Follow-Up

Background: Acetabular cage reconstruction with bone allografts is among the successful strategies to deal with massive acetabular bone loss. However, the nonbiological fixation nature of cages can compromise long-term success. Tantalum trabecular metal acetabular cups (TM cups) have been used in acetabular revision surgery because of their increased initial stability and good bone ingrowth features. This study was performed to determine whether the bone stock of the acetabulum is enough to support a hemispheric TM cup after failed cage reconstruction with bone allografts. Methods: We retrospectively reviewed patients who received acetabular revision surgery with TM cups after failed cage reconstruction with bone allografts from 2006 to 2017. There were 12 patients (5 males and 7 females) included in this study, with a mean age of 61.5 years (38 to 81) at the time of re-revision surgery. The mean follow-up after re-revision surgery was 8.6 years (2.6 to 13.3). The endpoint was defined as the aseptic loosening of the TM cup and reoperation for any causes. The change in bone stock of the acetabulum between index revision and re-revision was assessed according to the Gross classification for acetabular bone loss. Results: One patient died after eight years of follow-up of a cause not related to hip surgery. Two patients received two-stage revision arthroplasty due to PJI after 3.2 and 9.4 years of follow-up, respectively. The bone stock of the acetabulum was significantly improved between index revision and re-revision surgery (p < 0.0001). The Kaplan−Meier survivorship was 100% with aseptic loosening as the endpoint and 90% and 75% at five- and ten-year follow-up, respectively, with reoperation for any reason as the endpoint. Even cage reconstruction with bone allografts will fail eventually, and the bone stock of the acetabulum will improve after union and incorporation between host bone and allografts. The restored bone stocks will facilitate further revision surgery with hemispheric TM cups. The biological fixation between host bone and tantalum trabecular metal can provide longstanding stability of the TM cup. Conclusions: The results of our study offer a viable option for patients with failed cage reconstruction with bone allografts.

Therapeutic Treatments for Osteoporosis-Which Combination of Pills Is the Best among the Bad?

Osteoporosis is a chronical, systemic skeletal disorder characterized by an increase in bone resorption, which leads to reduced bone density. The reduction in bone mineral density and therefore low bone mass results in an increased risk of fractures. Osteoporosis is caused by an imbalance in the normally strictly regulated bone homeostasis. This imbalance is caused by overactive bone-resorbing osteoclasts, while bone-synthesizing osteoblasts do not compensate for this. In this review, the mechanism is presented, underlined by in vitro and animal models to investigate this imbalance as well as the current status of clinical trials. Furthermore, new therapeutic strategies for osteoporosis are presented, such as anabolic treatments and catabolic treatments and treatments using biomaterials and biomolecules. Another focus is on new combination therapies with multiple drugs which are currently considered more beneficial for the treatment of osteoporosis than monotherapies. Taken together, this review starts with an overview and ends with the newest approaches for osteoporosis therapies and a future perspective not presented so far.

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.

[Rehabilitation of orphan diseases in adulthood: osteogenesis imperfecta]

Osteogenesis imperfecta (brittle bone disease) is an orphan disease caused by a genetic mutation in collagen metabolism. Bone fractures are the most common symptoms; however, the clinical manifestation can vary widely. Additional features can include blue sclera, dwarfism, bone deformities, muscular weakness, scoliosis, hearing loss and hypermobility of joints. Most patients show a reduction of skeletal function. This leads to an increased risk of being unable to continue their former work and to participate in social life. A comprehensive treatment includes drug therapy, surgery and rehabilitation. This article gives an overview of the current status of rehabilitation in adult patients with osteogenesis imperfecta.

Suspension arthroplasty in the treatment of thumb carpometacarpal osteoarthritis

Literature presents several examples of surgical techniques for the treatment of carpometacarpal osteoarthritis. In our study we used a modified Ceruso's suspended arthroplasty technique. In this study, 53 patients from 2011 to 2017 underwent arthroplasty with trapezius excision and suture suspension between abductor pollicis longus and flexor carpi radialis. The average age at surgery was 69, the participants were 43 women and 10 men. The average total operation time was 59 minutes. The modified CMC suspension arthroplasty technique provides excellent results compared with those in the literature.

Atypical periprosthetic femoral fractures of the hip: characterisation of three cases

INTRODUCTION

Long-term use of bisphosphonates (BPs) has been associated with a specific type of tensile side femoral stress fracture known as Atypical Femoral Fracture (AFF). Theoretically periprosthetic femoral fractures (PFF) should be excluded from the diagnosis of AFF. However, emerging evidence correlates prolonged BPs use with the occurrence of a type of PFF with an atypical pattern (atypical PFF, APFF). The aim of the present study is to report 3 cases of APFF treated at a single centre.

METHODS

Clinical and radiographic records of PFF that occurred between January 2016 and August 2018 were retrospectively reviewed. All patients meeting the American Society for Bone and Mineral Research (ASBMR) criteria for definition of PFF were included. Management strategies for APFF and patient outcomes, including fracture healing and hip function (assessed by the Oxford Hip Score [OHS]) were collected.

RESULTS

3 patients in the study period were identified as APFF (1 incomplete, 2 complete). All patients were females with a mean age of 83.3 years. All patients were treated with lateral plating. The application of a contralateral strut allograft resulted in fracture healing in cases of complete fractures. Mean OHS at final follow-up was 34.3.

CONCLUSIONS

Despite occurring around a hip stem like PFF, APFF had peculiar clinical and radiographic features, making them more similar to AFF. Therefore, the orthopaedic surgeon should also consider the natural history and healing problems associated with AFF prior in order to choose the most appropriate management for APFF.

Osteogenesis imperfecta: advancements in genetics and treatment

PURPOSE OF REVIEW

The purpose of this review is to outline the current understanding of the molecular mechanisms and natural history of osteogenesis imperfecta, and to describe the development of new treatments for this disorder.

RECENT FINDINGS

The introduction of next-generation sequencing technology has led to better understanding of the genetic cause of osteogenesis imperfecta and enabled cost-effective and timely diagnosis via expanded gene panels and exome or genome sequencing. Clinically, despite genetic heterogeneity, different forms of osteogenesis imperfecta share similar features that include connective tissue and systemic manifestations in addition to bone fragility. Thus, the goals of treatment in osteogenesis imperfecta extend beyond decreasing the risk of fracture, to include the maximization of growth and mobility, and the management of extraskeletal complications. The standard of care in pediatric patients is bisphosphonates therapy. Ongoing preclinical studies in osteogenesis imperfecta mouse models and clinical studies in individuals with osteogenesis imperfecta have been instrumental in the development of new and targeted therapeutic approaches, such as sclerostin inhibition and transforming growth factor-β inhibition.

SUMMARY

Osteogenesis imperfecta is a skeletal dysplasia characterized by bone fragility and extraskeletal manifestations. Better understanding of the mechanisms of osteogenesis imperfecta will enable the development of much needed targeted therapies to improve the outcome in affected individuals.

Osteogenesis Imperfecta: New Perspectives From Clinical and Translational Research

Osteogenesis imperfecta (OI) is a monogenic bone fragility disorder that usually is caused by mutations in one of the two genes coding for collagen type I alpha chains, COL1A1 or COL1A2. Mutations in at least 18 other genes can also lead to an OI phenotype. As genetic testing is more widely used, mutations in these genes are also more frequently discovered in individuals who have a propensity for fractures, but who do not have other typical clinical characteristics of OI. Intravenous bisphosphonate therapy is still the most widely used drug treatment approach. Preclinical studies in OI mouse models have shown encouraging effects when the antiresorptive effect of a bisphosphonate was combined with bone anabolic therapy using a sclerostin antibody. Other novel experimental treatment approaches include inhibition of transforming growth factor beta signaling with a neutralizing antibody and the inhibition of myostatin and activin A by a soluble activin receptor 2B. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research

Current concepts in osteogenesis imperfecta: bone structure, biomechanics and medical management

The majority of patients with osteogenesis imperfecta (OI) have mutations in the COL1A1 or COL1A2 gene, which has consequences for the composition of the bone matrix and bone architecture. The mutations result in overmodified collagen molecules, thinner collagen fibres and hypermineralization of bone tissue at a bone matrix level. Trabecular bone in OI is characterized by a lower trabecular number and connectivity as well as a lower trabecular thickness and volumetric bone mass. Cortical bone shows a decreased cortical thickness with less mechanical anisotropy and an increased pore percentage as a result of increased osteocyte lacunae and vascular porosity. Most OI patients have mutations at different locations in the COL1 gene. Disease severity in OI is probably partly determined by the nature of the primary collagen defect and its location with respect to the C-terminus of the collagen protein. The overall bone biomechanics result in a relatively weak and brittle structure. Since this is a result of all of the above-mentioned factors as well as their interactions, there is considerable variation between patients, and accurate prediction on bone strength in the individual patient with OI is difficult. Current treatment of OI focuses on adequate vitamin-D levels and interventions in the bone turnover cycle with bisphosphonates. Bisphosphonates increase bone mineral density, but the evidence on improvement of clinical status remains limited. Effects of newer drugs such as antibodies against RANKL and sclerostin are currently under investigation. This paper was written under the guidance of the Study Group Genetics and Metabolic Diseases of the European Paediatric Orthopaedic Society.

Special form of osteoporosis in a 53-year-old man

Male osteoporosis often remains unrecognised. Osteoporotic fractures occur approximately 10 years later in men than in women due to higher peak bone mass. However, 30% of all hip fractures occur in men. Risk factors of osteoporotic fractures can be grouped into primary and secondary causes. We present the case of a 53-year-old man, who suffered a compression fracture of a lumbar vertebra after a generalised seizure and an atraumatic rib fracture 5 months later. We could exclude secondary causes of bone mineral loss such as primary hyperparathyroidism, glucocorticoid use and hypogonadism. However, a heterozygous missense mutation of the COL1A1 gene in exon 48 in further search of a secondary cause was found. Therapy was changed from bisphosphonate treatment to teriparatide. Considering the lack of other osteogenesis imperfecta (OI) symptoms and signs, the patient's illness can be classified as mild. OI should be considered as differential diagnosis in unexplained cases with osteoporosis.

Osteogenesis imperfecta and therapeutics

Osteogenesis imperfecta, or brittle bone disease, is a congenital disease that primarily causes low bone mass and bone fractures but it can negatively affect other organs. It is usually inherited in an autosomal dominant fashion, although rarer recessive and X-chromosome-linked forms of the disease have been identified. In addition to type I collagen, mutations in a number of other genes, often involved in type I collagen synthesis or in the differentiation and function of osteoblasts, have been identified in the last several years. Seldom, the study of a rare disease has delivered such a wealth of new information that have helped our understanding of multiple processes involved in collagen synthesis and bone formation. In this short review I will describe the clinical features and the molecular genetics of the disease, but then focus on how OI dysregulates all aspects of extracellular matrix biology. I will conclude with a discussion about OI therapeutics.