Bisphosphonate therapy for osteogenesis imperfecta

Functional outcomes of an adult with osteogenesis imperfecta after rehabilitation post bilateral Girdlestone procedure

This is a case of a 54-year-old woman managed as a case of osteogenesis imperfecta type 1 who sustained a left subtrochanteric fracture and eventual ankylosis of both hips after surgery and immobilisation. These injuries rendered her bedridden, maximally assisted in transitions and transfers, and unable to be positioned past 30° of backrest elevation. The patient underwent a bilateral Girdlestone procedure and had tailored progressive postoperative rehabilitation in both the inpatient and outpatient settings. The patient also continued to receive bisphosphonates during her preoperative and postoperative period, to improve bone stock and aid in relieving pain. Through the efforts of a team of physiatrists, geneticists and orthopaedic surgeons, the patient was able to achieve pain-free sitting, independent transitions and short-distance ambulation, which have allowed her to care for herself more effectively and return to her work and activities of daily living.

Survey of MRI Usefulness for the Clinical Assessment of Bone Microstructure

Bone microarchitecture has been shown to provide useful information regarding the evaluation of skeleton quality with an added value to areal bone mineral density, which can be used for the diagnosis of several bone diseases. Bone mineral density estimated from dual-energy X-ray absorptiometry (DXA) has shown to be a limited tool to identify patients' risk stratification and therapy delivery. Magnetic resonance imaging (MRI) has been proposed as another technique to assess bone quality and fracture risk by evaluating the bone structure and microarchitecture. To date, MRI is the only completely non-invasive and non-ionizing imaging modality that can assess both cortical and trabecular bone in vivo. In this review article, we reported a survey regarding the clinically relevant information MRI could provide for the assessment of the inner trabecular morphology of different bone segments. The last section will be devoted to the upcoming MRI applications (MR spectroscopy and chemical shift encoding MRI, solid state MRI and quantitative susceptibility mapping), which could provide additional biomarkers for the assessment of bone microarchitecture.

[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.

Bone density, fractures and the associated factors in iranian children and adolescent with Osteogenesis Imperfecta

Backround

Osteogenesis imperfecta(OI) is a frequent bone fragility disorder in children. The purpose of this study was to assess the BMD and Vitamin D level in children with OI in southern Iran.

Method

This case-control study was conducted on 23 children, clinically diagnosed as osteogenesis imperfecta and 23 age- and gender-matched healthy controls. Demographic and anthropometric data, biochemical parameters, puberty, sun exposure and physical activity were assessed. Bone mineral density (BMD) was measured by Dual-energy X-ray absorptiometry (DXA). Data analysis was done by SPSS22.

Results

Forty-three point four percent of OI patients and fifty-six point five percent of control group had vitamin D deficiency (P = 0.376). Thirteen OI patients (56%) had low bone mass for chronological age in lumbar area (P < 0.001). Fracture episodes during treatment was significantly influenced by time of Pamidronate start, courses of Pamidronate injection, puberty and sun exposure (P values = 0.015, 0.030, 0.044 and 0.032, respectively). Fracture episodes during treatment had significantly increased in patients who had received Pamidronate more than 3 years compared with those received less than 3 years(P values = 0.047).

Conclusions

This study showed that vitamin D deficiency is prevalent amongst OI children in southern Iran. More than half of the OI children had low bone mass for chronological age in lumbar area, despite receiving bisphosphonate therapy. The present results revealed that early initiation of Pamidronate and number of Pamidronate courses are associated with lower fracture rate. However, treatment period more than 3 years can have adverse effect on fracture rates.

Mechanisms of Bone Fragility: From Osteogenesis Imperfecta to Secondary Osteoporosis

Bone material strength is determined by several factors, such as bone mass, matrix composition, mineralization, architecture and shape. From a clinical perspective, bone fragility is classified as primary (i.e., genetic and rare) or secondary (i.e., acquired and common) osteoporosis. Understanding the mechanism of rare genetic bone fragility disorders not only advances medical knowledge on rare diseases, it may open doors for drug development for more common disorders (i.e., postmenopausal osteoporosis). In this review, we highlight the main disease mechanisms underlying the development of human bone fragility associated with low bone mass known to date. The pathways we focus on are type I collagen processing, WNT-signaling, TGF-ß signaling, the RANKL-RANK system and the osteocyte mechanosensing pathway. We demonstrate how the discovery of most of these pathways has led to targeted, pathway-specific treatments.

Osteogenesis Imperfecta in neonatal period in Cameroon: A case report

Early forms of Osteogenesis Imperfecta should be considered as main etiology of bone deformities in newborns. Prenatal diagnosis and genetic counseling should be improved in Africa. Management of these children remains difficult in low-income countries.

Case Report: Locking Plate for Cubitus Varus Correction in a 7-Year-Old Girl With Osteogenesis Imperfecta

Background: Cubitus varus deformity is a common complication of untreated elbow fractures in children. However, cubitus varus in osteogenesis imperfecta (OI) children is a rare but challenging situation. To the author's knowledge, this is the first study discussing the correction of cubitus varus deformity in patient with OI. Case Presentation: Here we report a case of a 7-year-old OI girl with cubitus varus deformity due to a supracondylar fracture of humerus 3 year ago. The patient's parent gave a history of supracondylar fracture of left humerus in 2015. Without medical intervention, the patient was admitted into our institution for corrective surgery with the diagnosis of osteogenesis imperfecta and cubitus varus deformity in the left arm. Result: Medications including calcium, vitamin D and bisphosphonates were administered before the corrective surgery of cubitus varus, and a single locking plate was used to fixate the osteotomy. After the surgery, the appearance and range of motion (ROM) of the left arm was almost normal. Combined with gradual rehabilitation, the ROM of the left arm was normal without pain during daily use within the 1-year follow up. The hardware was removed as the nailing of the forearm fractures was performed at the same time. In the latest follow-up in September 2021, the appearance and ROM of the left arm was normal. Conclusion: Cubitus varus is a common deformity in children with elbow injuries, but it presents a challenging situation in compound fractures in OI patients. Locking plate combined with meticulous pharmacological intervention provides a good option for corrective surgery of cubitus varus in patients with OI.

Oral Ibandronate Therapy in Three Patients with Osteogenesis Imperfecta

INTRODUCTION

Treatment with orally administered ibandronate is an effective way to increase bone mineral density (BMD) and reduce fracture rate in post-menopausal women and in men with osteoporosis. There are only very few reports concerning ibandronate therapy in children and adolescents, and in patients with osteogenesis imperfecta (OI), as bisphosphonates are not registered for therapeutic use in pediatrics.

CASE REPORT

We present three patients with OI, where once-monthly oral ibandronate increased spinal BMD after two and four years, respectively, of therapy without any occurrence of new fractures and no adverse reactions. Somatic growth was not affected by the ibandronate treatment.

CONCLUSION

Once-monthly oral ibandronate increased BMD and most probably improved bone quality in young patients with OI.

Management of Osteogenesis Imperfecta: A Multidisciplinary Comprehensive Approach

Osteogenesis imperfecta (OI) is characterized by recurring fractures and limb and spine deformities. With the advent of medical therapeutics and the discovery of causative genes, as well as the introduction of a newly devised intramedullary rod, the general condition and ambulatory function of patients diagnosed with OI have been improved over the past decades. This review covers recent developments in research and management of OI.

Management of primary and secondary osteoporosis in children

Osteoporosis in children differs from adults in terms of definition, diagnosis, monitoring and treatment options. Primary osteoporosis comprises primarily of osteogenesis imperfecta (OI), but there are significant other causes of bone fragility in children that require treatment. Secondary osteoporosis can be a result of muscle disuse, iatrogenic causes, such as steroids, chronic inflammation, delayed or arrested puberty and thalassaemia major. Investigations involve bone biochemistry, dual-energy X-ray absorptiometry scan for bone densitometry and vertebral fracture assessment, radiographic assessment of the spine and, in some cases, quantitative computed tomography (QCT) or peripheral QCT. It is important that bone mineral density (BMD) results are adjusted based on age, gender and height, in order to reflect size corrections in children. Genetics are being used increasingly for the diagnosis and classification of various cases of primary osteoporosis. Bone turnover markers are used less frequently in children, but can be helpful in monitoring treatment and transiliac bone biopsy can assist in the diagnosis of atypical cases of osteoporosis. The management of children with osteoporosis requires a multidisciplinary team of health professionals with expertise in paediatric bone disease. The prevention and treatment of fragility fractures and improvement of the quality of life of patients are important aims of a specialised service. The drugs used most commonly in children are bisphosphonates, that, with timely treatment, can give good results in improving BMD and reshaping vertebral fractures. The data regarding their effect on reducing long bone fractures are equivocal. Denosumab is being used increasingly for various conditions with mixed results. There are more drugs trialled in adults, but these are not yet licenced for children. Increasing awareness of risk factors for paediatric osteoporosis, screening and referral to a specialist team for appropriate management can lead to early detection and treatment of asymptomatic fractures and prevention of further bone damage.

Osteoporose im Kindes- und Jugendalter

Osteoporose ist eine Erkrankung des Skelettapparats, die durch eine Beeinträchtigung der Knochenmikroarchitektur zu einer erhöhten Knochenbruchrate führt. Während Osteoporose im höheren Erwachsenenalter eine häufige Diagnose darstellt, wird der Osteoporose des Kindes- und Jugendalters erst seit relativ kurzer Zeit zunehmend Bedeutung zugesprochen. Generell werden zwei unterschiedliche Formen der Erkrankung unterschieden: Die primäre Osteoporose wird verursacht durch genetische Veränderungen in skelettrelevanten Genen, die häufigste Erkrankungsgruppe stellt die Osteogenesis imperfecta mit ursächlichen Mutationen im Kollagen-1-Gen dar. Internistische Maßnahmen umfassen neben funktionell-therapeutischen Maßnahmen auch pharmakologische Therapien mit Bisphosphonaten. Die sekundäre Osteoporose als Symptom chronischer Grunderkrankungen oder pharmakologischer Interventionen weist eine deutlich höhere Prävalenz als die primären Formen der Osteoporose auf. Abhängig von Pathomechanismus und Verlauf der Grunderkrankung kommt es zu osteoporotischen Symptomen unterschiedlichster Ausprägung. Die Therapiekonzepte müssen der individuellen Symptomatik angepasst werden, die Datenlage zum Einsatz von Bisphosphonaten ist deutlich geringer als bei der Osteogenesis imperfecta. Ziel dieses Artikels ist es, einen Überblick über Diagnostik und Therapie der sehr unterschiedlichen Formen der pädiatrischen Osteoporose sowie einen Einblick in die rezenten Entwicklungen für den primär und Sekundärversorgungsbereich zu geben.

Therapeutic Dimensions of Bisphosphonates: A Clinical Update

Bisphosphonates (BPs) are a commonly used class of drugs for the treatment of bone disorders. An extensive review of BPs with their clinical efficacy and safety profile is unavailable. This study aimed to review the available literature on BPs, summarize their role in clinical therapy, and emphasize their safety profile. Authors reviewed the existing literature using the Google Scholar, PubMed, and Micromedex databases and analyzed the collected articles. BPs are the preferred medication for osteoporosis and other similar conditions owing to their efficient antiosteoclastic activity. Few of them are available in oral dosage forms; hence, they are patient-friendly. The mechanism of action, common adverse effects and their clinical applications, precautions and warnings pertaining to the route of administration, and safety profiles have been discussed in this manuscript. The common adverse effects are majorly related to the gastrointestinal, cardiovascular, and endocrine system. Upon chronic usage, patients may experience serious problems like osteonecrosis of the jaw and atypical bone fractures. Although BPs are effective and safe, they may cause GI adverse effects and rare cases of osteonecrosis. Patient counseling could prove beneficial in early identification and prevention of the adverse effects associated with BPs.

Osteogenesis imperfecta-pathophysiology and therapeutic options

Osteogenesis imperfecta (OI) is a rare congenital disease with a wide spectrum of severity characterized by skeletal deformity and increased bone fragility as well as additional, variable extraskeletal symptoms. Here, we present an overview of the genetic heterogeneity and pathophysiological background of OI as well as OI-related bone fragility disorders and highlight current therapeutic options.

The most common form of OI is caused by mutations in the two collagen type I genes. Stop mutations usually lead to reduced collagen amount resulting in a mild phenotype, while missense mutations mainly provoke structural alterations in the collagen protein and entail a more severe phenotype. Numerous other causal genes have been identified during the last decade that are involved in collagen biosynthesis, modification and secretion, the differentiation and function of osteoblasts, and the maintenance of bone homeostasis.

Management of patients with OI involves medical treatment by bisphosphonates as the most promising therapy to inhibit bone resorption and thereby facilitate bone formation. Surgical treatment ensures pain reduction and healing without an increase of deformities. Timely remobilization and regular strengthening of the muscles by physiotherapy are crucial to improve mobility, prevent muscle wasting and avoid bone resorption caused by immobilization. Identification of the pathomechanism for SERPINF1 mutations led to the development of a tailored mechanism-based therapy using denosumab, and unraveling further pathomechanisms will likely open new avenues for innovative treatment approaches.

Finite element analysis of bone strength in osteogenesis imperfecta

As a dedicated experimentalist, John Currey praised the high potential of finite element (FE) analysis but also recognized its critical limitations. The application of the FE methodology to bone tissue is reviewed in the light of his enthusiastic and colorful statements. In the past decades, FE analysis contributed substantially to the understanding of structure-function properties in the hierarchical organization of bone and to the simulation of bone adaptation. The systematic experimental validation of FE analysis of bone strength in anatomical locations at risk of fracture led to its application in clinical studies to evaluate efficacy of antiresorptive or anabolic treatment of bone fragility. Beyond the successful analyses of healthy or osteoporotic bone, FE analysis becomes increasingly involved in the investigation of other fragility-related bone diseases. The case of osteogenesis imperfecta (OI) is exposed, the multiscale alterations of the bone tissue and the effect of treatment summarized. A few FE analyses attempting to answer open questions in OI are then reported. An original study is finally presented that explored the structural properties of the Brtl/+ murine model of OI type IV subjected to sclerostin neutralizing antibody treatment using microFE analysis. The use of identical material properties in the four-point bending FE simulations of the femora reproduced not only the experimental values but also the statistical comparisons examining the effect of disease and treatment. Further efforts are needed to build upon the extraordinary legacy of John Currey and clarify the impact of different bone diseases on the hierarchical mechanical properties of bone.

New perspectives on the treatment of skeletal dysplasia

The last few decades have been marked by the identification of numerous genes implicated in genetic disorders, helping in the elucidation of the underlying pathophysiology of these conditions. This has allowed new therapeutic approaches to emerge such as cellular therapy, gene therapy, or pharmacological therapy for various conditions. Skeletal dysplasias are good models to illustrate these scientific advances. Indeed, several therapeutic strategies are currently being investigated in osteogenesis imperfecta; there are ongoing clinical trials based on pharmacological approaches, targeting signaling pathways in achondroplasia and fibrodysplasia ossificans progressiva or the endoplasmic reticulum stress in metaphyseal dysplasia type Schmid or pseudoachondroplasia. Moreover, the treatment of hypophosphatasia or Morquio A disease illustrates the efficacy of enzyme drug replacement. To provide a highly specialized multidisciplinary approach, these treatments are managed by reference centers. The emergence of treatments in skeletal dysplasia provides new perspectives on the prognosis of these severe conditions and may change prenatal counseling in these diseases over the coming years.

Expert panel consensus recommendations for diagnosis and treatment of secondary osteoporosis in children

BACKGROUND

Osteoporosis incidence in children is increasing due to the increased survival rate of patients suffering from chronic diseases and the increased use of drugs that can damage bones. Recent changes made to the definition of childhood osteoporosis, along with the lack of guidelines or national consensuses regarding its diagnosis and treatment, have resulted in a wide variability in the approaches used to treat this disease. For these reasons, the Osteogenesis Imperfecta and Childhood Osteoporosis Working Group of the Spanish Society of Pediatric Rheumatology has sounded the need for developing guidelines to standardize clinical practice with regard to this pathology.

METHODS

An expert panel comprised of 6 pediatricians and 5 rheumatologists carried out a qualitative literature review and provided recommendations based on evidence, when that was available, or on their own experience. The level of evidence was determined for each section using the Oxford Centre for Evidence-based Medicine (CEBM) system. A Delphi survey was conducted for those recommendations with an evidence level of IV or V. This survey was sent to all members of the SERPE. All recommendations that had a level of agreement higher or equal to 70% were included.

RESULTS

Fifty-one recommendations, categorized into eight sections, were obtained. Twenty-four of them presented an evidence level 4 or 5, and therefore a Delphi survey was conducted. This was submitted electronically and received a response rate of 40%. All recommendations submitted to the Delphi round obtained a level of agreement of 70% or higher and were therefore accepted.

CONCLUSION

In summary, we present herein guidelines for the prevention, diagnosis and treatment of secondary childhood osteoporosis based on the available evidence and expert clinical experience. We believe it can serve as a useful tool that will contribute to the standardization of clinical practice for this pathology. Prophylactic measures, early diagnosis and a proper therapeutic approach are essential to improving bone health, not only in children and adolescents, but also in the adults they will become in the future.

Combination therapy in the Col1a2G610C mouse model of Osteogenesis Imperfecta reveals an additive effect of enhancing LRP5 signaling and inhibiting TGFβ signaling on trabecular bone but not on cortical bone

Enhancing LRP5 signaling and inhibiting TGFβ signaling have each been reported to increase bone mass and improve bone strength in wild-type mice. Monotherapy targeting LRP5 signaling, or TGFβ signaling, also improved bone properties in mouse models of Osteogenesis Imperfecta (OI). We investigated whether additive or synergistic increases in bone properties would be attained if enhanced LRP5 signaling was combined with TGFβ inhibition. We crossed an Lrp5 high bone mass (HBM) allele (Lrp5^A214V) into the Col1a2^G610C/+ mouse model of OI. At 6-weeks-of-age we began treating mice with an antibody that inhibits TGFβ1, β2, and β3 (mAb 1D11), or with an isotype-matched control antibody (mAb 13C4). At 12-weeks-old, we observed that combining enhanced LRP5 signaling with inhibited TGFβ signaling produced an additive effect on femoral and vertebral trabecular bone volumes, but not on cortical bone volumes. Although enhanced LRP5 signaling increased femur strength in a 3-point bending assay in Col1a2^G610C/+ mice, femur strength did not improve further with TGFβ inhibition. Neither enhanced LRP5 signaling nor TGFβ inhibition, alone or in combination, improved femur 3-point-bending post-yield displacement in Col1a2^G610C/+ mice. These pre-clinical studies indicate combination therapies that target LRP5 and TGFβ signaling should increase trabecular bone mass in patients with OI more than targeting either signaling pathway alone. Whether additive increases in trabecular bone mass will occur in, and clinically benefit, patients with OI needs to be determined.

Pretreatment with Pamidronate Decreases Bone Formation but Increases Callus Bone Volume in a Rat Closed Fracture Model

Clinical concerns have been raised over prior exposure to bisphosphonates impairing fracture healing. To model this, groups of male Wistar rats were assigned to saline control or treatment groups receiving 0.15 mg/kg (low dose), 0.5 mg/kg (medium dose), and 5 mg/kg (high dose) Pamidronate (PAM) twice weekly for 4 weeks. At this point, closed fractures were made using an Einhorn apparatus, and bisphosphonate dosing was continued until the experimental endpoint. Specimens were analyzed at 2 and 6 weeks (N = 8 per group per time point). Twice weekly PAM dosing was found to have no effect on early soft callus remodeling at 2 weeks post fracture. At this time point, the highest dose PAM group gave significant increases in bone volume (+ 10%, p < 0.05), bone mineral content (+ 30%, p < 0.01), and bone mineral density (+ 10%, p < 0.01). This PAM dosing regimen showed more substantive effects on hard callus at 6 weeks post fracture, with PAM treatment groups showing + 46-79% increased bone volume. Dynamic bone labeling showed reduced calcein signal in the PAM-treated calluses (38-63%, p < 0.01) and reduced MAR (32-49%, p < 0.01), suggesting a compensatory reduction in bone anabolism. These data support the concept that bisphosphonates lead to profound decreases in bone turnover in fracture repair, however, this does not affect soft callus remodeling.

6'-Methoxy Raloxifene-analog enhances mouse bone properties with reduced estrogen receptor binding

Raloxifene (RAL) is an FDA-approved drug used to treat osteoporosis in postmenopausal women. RAL suppresses bone loss primarily through its role as a selective estrogen receptor modulator (SERM). This hormonal estrogen therapy promotes unintended side effects, such as hot flashes and increased thrombosis risk, and prevents the drug from being used in some patient populations at-risk for fracture, including children with bone disorders. It has recently been demonstrated that RAL can have significant positive effects on overall bone mechanical properties by binding to collagen and increasing bone tissue hydration in a cell-independent manner. A Raloxifene-Analog (RAL-A) was synthesized by replacing the 6-hydroxyl substituent with 6-methoxy in effort to reduce the compound's binding affinity for estrogen receptors (ER) while maintaining its collagen-binding ability. It was hypothesized that RAL-A would improve the mechanical integrity of bone in a manner similar to RAL, but with reduced estrogen receptor binding. Molecular assessment showed that while RAL-A did reduce ER binding, downstream ER signaling was not completely abolished. In-vitro, RAL-A performed similarly to RAL and had an identical concentration threshold on osteocyte cell proliferation, differentiation, and function. To assess treatment effect in-vivo, wildtype (WT) and heterozygous (OIM+/−) female mice from the Osteogenesis Imperfecta (OI) murine model were treated with either RAL or RAL-A from 8 weeks to 16 weeks of age. There was an untreated control group for each genotype as well. Bone microarchitecture was assessed using microCT, and mechanical behavior was assessed using 3-point bending. Results indicate that both compounds produced analogous gains in tibial trabecular and cortical microarchitecture. While WT mechanical properties were not drastically altered with either treatment, OIM+/− mechanical properties were significantly enhanced, most notably, in post-yield properties including bone toughness. This proof-of-concept study shows promising results and warrants the exploration of additional analog iterations to further reduce ER binding and improve fracture resistance.

Plethora of Traumatic Lesions of Bilateral Knee Extensor Mechanism in Osteogenesis Imperfecta

INTRODUCTION

Injuries to the quadriceps extensor mechanism are rare in patients with Osteogenesis Imperfecta (OI). To the best of our knowledge, non-union of the patella in OI, either as an isolated problem or in combination with an acute fracture, has not been previously reported.

CASE REPORT

We describe how we surgically approached both the fracture and the non-union simultaneously. The surgical technique and steps are described in detail. Post-operative course was uneventful and the outcome was favorable, with full return of function for the patient.

CONCLUSION

A review of various knee extensor mechanism injuries in OI is described as illustrated in a single patient. The unusual simultaneous surgical treatment of a non-union and an acute fracture in the same patella shows that despite the severely compromised bone in this rare bone disease the bone still has a capacity to heal with a functional outcome.

Impact of fracture characteristics and disease-specific complications on health-related quality of life in osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a connective tissue disease with bone fragility. Several studies have indicated that physical function in adult OI was correlated to the disease severity, but there have been no reports delineating the impact of the fracture characteristics and disease-specific complications on health-related quality of life (HRQoL). The purpose of this study is to clarify the factors impacted on HRQoL in adult OI patients. We conducted a cross-sectional study between July 2016 and March 2018 and sent a questionnaire regarding HRQoL using Short Form-36 (SF-36) to the OI patients at the age of 20 years or older who had a medical history of the investigators' institutions. The 40 patients completely answered the SF-36. Mental component summary and role/social component summary were unremarkable. Physical component summary (PCS) was significantly associated with z-score for height, teeth abnormality, and cardiopulmonary insufficiency (partial regression coefficient, 3.04, - 9.70, and - 11.35; p, < 0.001, 0.047, and 0.025, respectively). PCS was also significantly lower in the patients who had an initial fracture before the age of 2 years than those without occurrence of fractures until 2 years old (25.80 ± 17.15 versus 44.20 ± 16.54; p = 0.002), or those who had lower extremity fractures more than five times as compared with normal populations. Physical function was decreased in OI patients who had fractures before 2 years old, especially in lower extremity. Appropriate medical managements for cardiopulmonary insufficiency are required not only to maintain physical function but also to decrease mortality.

The evolving therapeutic landscape of genetic skeletal disorders

BACKGROUND

Rare bone diseases account for 5% of all birth defects yet very few have personalised treatments. Developments in genetic diagnosis, molecular techniques and treatment technologies however, are leading to unparalleled therapeutic advance. This review explores the evolving therapeutic landscape of genetic skeletal disorders (GSDs); the key conditions and there key differentials.

METHODS

A retrospective literature based review was conducted in December 2018 using a systematic search strategy for relevant articles and trials in Pubmed and clinicaltrials.gov respectively. Over 140 articles and 80 trials were generated for review.

RESULTS

Over 20 personalised therapies are discussed in addition to several novel disease modifying treatments in over 25 GSDs. Treatments discussed are at different stages from preclinical studies to clinical trials and approved drugs, including; Burosumab for X-linked hypophosphatemia, Palovarotene for Hereditary Multiple Exostoses, Carbamazepine for Metaphyseal Chondrodysplasia (Schmid type), Lithium carbonate and anti-sclerostin therapy for Osteoporosis Pseudoglioma syndrome and novel therapies for Osteopetrosis. We also discuss therapeutic advances in Achondroplasia, Osteogenesis Imperfecta (OI), Hypophosphotasia (HPP), Fibrodysplasia Ossificans Progressiva, and RNA silencing therapies in preclinical studies for OI and HPP.

DISCUSSION

It is an exciting time for GSD therapies despite the challenges of drug development in rare diseases. In discussing emerging therapies, we explore novel approaches to drug development from drug repurposing to in-utero stem cell transplants. We highlight the improved understanding of bone pathophysiology, genetic pathways and challenges of developing gene therapies for GSDs.

Neuromuscular Diseases and Bone

Neuromuscular diseases (NMDs) are inherited or acquired conditions affecting skeletal muscles, motor nerves, or neuromuscular junctions. Most of them are characterized by a progressive damage of muscle fibers with reduced muscle strength, disability, and poor health-related quality of life of affected patients. In this scenario, skeletal health is usually compromised as a consequence of modified bone-muscle cross-talk including biomechanical and bio-humoral issues, resulting in increased risk of bone fragility and fractures. In addition, NMD patients frequently face nutritional issues, including malnutrition due to feeding disorders and swallowing problems that might affect bone health. Moreover, in these patients, low levels of physical activity or immobility are common and might lead to overweight or obesity that can also interfere with bone strength features. Also, vitamin D deficiency could play a critical role both in the pathogenesis and in the clinical scenario of many NMDs, suggesting that its correction could be useful in maintaining or enhancing bone health, especially in the early phases of NMDs. Last but not least, specific disease-modifying drugs, available for some NMDs, are frequently burdened with adverse effects on bone tissue. For example, glucocorticoid therapy, standard of care for many muscular dystrophies, prolongs long-term survival in treated patients; nevertheless, high dose and/or chronic use of these drugs are a common cause of secondary osteoporosis. This review addresses the current state of knowledge about the factors that play a role in determining bone alterations reported in NMDs, how these factors can modify the biological pathways underlying bone health, and which are the available interventions to manage bone involvement in patients affected by NMDs. Considering the complexity of care of these patients, an interdisciplinary and multimodal management strategy based on both pharmacological and non-pharmacological interventions is recommended, particularly targeting musculoskeletal issues that are closely related to functional independence as well as social implications.

Individualized treatment with denosumab in children with osteogenesis imperfecta - follow up of a trial cohort

Background

Osteogenesis imperfecta (OI) is a rare disease leading to hereditary bone fragility. Nearly 90% of cases are caused by mutations in the collagen genes COL1A1/A2 (classical OI) leading to multiple fractures, scoliosis, short stature and nonskeletal findings as blue sclera, hypermobility of joints, bone pain and delayed motor function development. Bisphosphonates are used in most moderate and severely affected patients assuming that an increase of bone mineral density might reduce fractures and bone pain in patients with OI. Denosumab as a RANK ligand antibody inhibiting osteoclast maturation has been approved for osteoporosis treatment in adults. First data from small clinical trials promised a high efficacy of Denosumab in children with OI. Aim of this analysis was a retrospective evaluation of an individualized biomarker-associated treatment regime with Denosumab in 10 children with classical OI which were followed for 1 year after their participation in a pilot trial with Denosumab. Therefore urinary deoxypyridinoline levels were evaluated frequently as an osteoclastic activity marker and depending on that levels Denosumab injections were scheduled individually.

Methods

Ten patients (age range: 6.16–12.13 years; all participated in the former OI-AK phase 2 trial (NCT01799798)) were included in the follow-up period. Denosumab was administered subcutaneously depending on the individual urinary excretion course of deoxypyridinoline (DPD/Crea) as osteoclastic activity marker with 1 mg/kg body weight. DPD/Crea levels were evaluated before denosumab administration and afterwards. If patients present after an initial decrease after injection with a re-increase up to the DPD/crea level before Denosumab injection next dosage was planned. Changes of areal bone mineral density (aBMD) using dual energy x-ray absorptiometry of the lumbar spine after 12 month was evaluated. Safety was assessed by bone metabolism markers and side effect reporting.

Results

During follow-up mean relative change of lumbar aBMD was − 6.4%. Lumbar spine aBMD z-Scores decreased from − 1.01 ± 2.61 (mean ± SD) to − 1.91 ± 2.12 (p = 0.015). Mobility changed not significantly (GMFM-88 -6.49 ± 8.85% (p = 0.08). No severe side effects occurred. Dose intervals could be extended in the mean from 12 weeks previously to 20.3 weeks.

Conclusions

On average, it was possible to prolong the intervals between drug administrations and to reduce the total dose about by 25% without a decrease of mobility or change of vertebral shape despite a reduction of lumbar aBMD during 1 year of biomarker-directed Denosumab treatment. Further trials are necessary to balance side effects and highest efficacy in children.

Validation of the Adolescent Pediatric Pain Tool for the Multidimensional Measurement of Pain in Children and Adolescents Diagnosed with Osteogenesis Imperfecta

Background: The Adolescent Pediatric Pain Tool (APPT) is a self-reported, multidimensional assessment of pain location, intensity, and quality in children and adolescents. Yet, it has not been validated for use in children and adolescents with osteogenesis imperfecta (OI). Aims: This study aimed to validate and evaluate the feasibility of the APPT for pain assessment in children and adolescents with OI. Methods: A prospective observational study was conducted at a university-affiliated pediatric hospital in Canada. Thirty-three children and adolescents with OI participated by completing the APPT pre-bisphosphonate intravenous infusion and 1 week post-bisphosphonate intravenous infusion. Main outcomes were internal consistency, convergent and discriminative validity, and feasibility. Results: The Kuder-Richardson test of internal consistency was 0.863, 0.661, and 0.729 for the Sensory, Affective, and Evaluative subscales, respectively. For the entire pain quality scale, the Cronbach's alpha was 0.835. Regarding convergent validity, a moderate correlation was observed between the ratings on the pain intensity scale and the Faces Pain Scale-Revised (Spearman's rho = 0.711). Patients for whom pain was a problem reported higher pain intensity (Mann Whitney U = 41.50, P = 0.032) and more pain quality descriptors (Mann Whitney U = 45.50, P = 0.020) and painful body areas (Mann-Whitney U = 25.50, P = 0.001) than those for whom it was not (Mann-Whitney U, P < 0.05). In terms of feasibility, completing the tool may require a considerable time commitment and assistance from a clinician or parent, especially if the patient is experiencing pain and provides detailed pain location and quality information by completing the APPT. Conclusions: This study suggests that the APPT is valid for the multidimensional assessment of pain in children and adolescents with OI, but feasibility needs to be enhanced.

Expanding the phenotypic spectrum of osteogenesis imperfecta type V including heterotopic ossification of muscle origins and attachments

Background

Osteogenesis imperfecta (OI) is a clinical and genetic heterogeneous group of connective tissue disorders, characterized by bone fragility and a propensity to fracture.

Methods

In this report we describe the clinical phenotype of two patients, a 28‐year‐old woman and her mother (54 years old), both with a history of short stature and multiple fractures.

Results

Exome sequencing revealed the recurring IFITM5:c.‐14 C>T variant causing OI type V. Both patients had several fractures during childhood. CT‐scan and scintigraphy showed ossification of the origin and attachment of muscles and hypertrophic callus formation.

Conclusion

Ossification of the origin and attachment of muscles seems to be part of the phenotype in patients with OI type V.

Cyclic pamidronate treatment for osteogenesis imperfecta: Report from a Brazilian reference center

Treatment of moderate and severe forms of osteogenesis imperfecta (OI) with cyclic pamidronate at the Reference Center for OI Treatment in Southern Brazil was studied. A retrospective cohort study was conducted from 2002 to 2012. Data were obtained during inpatient (drug infusion) and outpatient care. Clinical data, including the presence of blue sclerae, dentinogenesis imperfecta, history and site of the fractures, biochemical data, including calcium, phosphorus, and alkaline phosphatase levels, were systematically collected. Bone mineral density (BMD) was measured using dual energy X-ray absorptiometry (DXA). Forty-five patients (26 females) were included in the study, and the age of the patients at the time of diagnosis ranged from 1 to 144 months, with a median age (p25-p75) of 38 (5-96) months. Most cases presented OI-4 (51.1%), and the median age of the patients at the start of treatment was 3.3 years (25-75 percentiles: 0.5 - 8.7 years). Twenty-four patients (54.5%) had some adverse events or intercurrences during treatment, and the treatment compliance mean was 92.3% (± 10.7). The treatment with intravenous pamidronate has shown to be safe, well-tolerated, and effective in regard to the improvement of BMD and the reduction of the number of fractures in children and adolescents with OI.

Osteogenesis Imperfecta: A Pediatric Orthopedic Perspective

Osteogenesis imperfecta is a genetically and phenotypically heterogeneous disorder related to a defect or deficiency in the production of type I collagen. It is characterized by brittle bones, fractures, spine and extremity deformity, and a host of extraskeletal manifestations. Type I collagen is present in bone, tendons, ligaments, skin, dentin, and the sclera of the eye and other connective tissues. Osteogenesis imperfecta includes a multitude of disease manifestations that may be present at birth or develop over time and vary depending on the severity of the disease. This article describes the disease presentation and management considerations from a pediatric orthopedic perspective.

The effect of bisphosphonate medication on orthodontics and orthognathic surgery in patients with osteogenesis imperfecta

Introduction: Osteogenesis imperfecta (OI) is a genetic disease that primarily affects bone formation and metabolism. Craniofacial malformations belong to the broad spectrum of the OI phenotype. The introduction of bisphosphonate medications was intended to counteract the significant brittleness of the bones of OI patients. In connection with the application of bisphosphonates, drug-associated osteonecrosis of the jaw has become known as an undesirable effect of the therapeutically intended reduction of osteoclast activity. Originally, the pharmacological inhibition of bone loss was mainly used in oncological therapy. For some time now, osteoporosis has also been treated with substances that inhibit bone resorption.

In OI, malposition of the jaws is relatively common, in particular retrognathia of the maxilla and progeny of the mandible. The literature discloses complications of orthognathic surgery in OI patients. Previous literature reviews suggest that bisphosphonate medication has no significant impact on the performance of and healing after oral surgery in OI patients.

Materialandmethods: An essential prerequisite of a therapy adapted to the patient’s condition is the knowledge of the patient's medical history. This case report describes the orthodontic-surgical treatment of an OI patient and the treatment experience derived in dealing with the condition. The unusual circumstance of this case is that the patient had concealed both his underlying disease and his medication during the current treatment period. In addition, the relevant literature is evaluated for combining the keywords OI, orthodontic therapy, bisphosphonates, and orthognathic surgery.

Results: Based on the literature and our own experience, it is concluded that orthodontic treatment with bisphosphonate medication can also be carried out in OI patients. However, considerably greater forces and longer time intervals should be scheduled for each treatment. Orthognathic surgery with bisphosphonate medication turned out to be uncomplicated in our own case, considering the underlying disease in the planning of surgical procedures. However, there have been very few reports of OI patients in whom orthodontic-surgical treatment of jaw malformation has been performed with bisphosphonate medication.

Conclusion: Taking into account the reported experience of severe complications of orthognathic surgery, the multiple documented adjustments to the treatment strategy of OI patients should be taken seriously. The basic condition of therapy adapted to the disease is that the patient informs the practitioner in an appropriate manner about his or her state of health.

Genotype-phenotype correlation study in 364 osteogenesis imperfecta Italian patients

Osteogenesis imperfecta (OI) is a rare genetic disorder of the connective tissue and 90% of cases are due to dominant mutations in COL1A1 and COL1A2 genes. To increase OI disease knowledge and contribute to patient follow-up management, a homogeneous Italian cohort of 364 subjects affected by OI types I–IV was evaluated. The study population was composed of 262 OI type I, 24 type II, 39 type III, and 39 type IV patients. Three hundred and nine subjects had a type I collagen affecting function mutations (230 in α1(I) and 79 in α2(I)); no disease-causing changes were noticed in 55 patients. Compared with previous genotype–phenotype OI correlation studies, additional observations arose: a new effect for α1- and α2-serine substitutions has been pointed out and heart defects, never considered before, resulted associated to quantitative mutations (P = 0.043). Moreover, some different findings emerged if compared with previous literature; especially, focusing the attention on the lethal form, no association with specific collagen regions was found and most of variants localized in the previously reported “lethal clusters” were causative of OI types I–IV. Some discrepancies have been highlighted also considering the “50–55 nucleotides rule,” as well as the relationship between specific collagen I mutated region and the presence of dentinogenesis imperfecta and/or blue sclera. Despite difficulties still present in defining clear rules to predict the clinical outcome in OI patients, this study provides new pieces for completing the puzzle, also thanks to the inclusion of clinical signs never considered before and to the large number of OI Italian patients.

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.

A Multicenter Observational Cohort Study to Evaluate the Effects of Bisphosphonate Exposure on Bone Mineral Density and Other Health Outcomes in Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is characterized by low bone mass and bone fragility. Using data from a large cohort of individuals with OI from the Osteogenesis Imperfecta Foundation's linked clinical research centers, we examined the association between exposure to bisphosphonate (BPN) treatment (past or present) and lumbar spine (LS) areal bone mineral density (aBMD), fractures, scoliosis, and mobility. From 466 individuals, we obtained 1394 participant‐age LS aBMD data points. Though all OI subtypes were examined, primary analyses were restricted to type I OI (OI‐1). Using linear regression, we constructed expected OI‐1 LS aBMD‐for‐age curves from the data from individuals who had never received BPN. LS aBMD in those who had been exposed to BPN was then compared with the computed expected aBMD. BPN exposure in preadolescent years (age <14 years) was associated with a LS aBMD that was 9% more than the expected computed values in BPN‐naïve individuals (p < 0.01); however, such association was not observed across all ages. Exposure to i.v. BPN and treatment duration >2 years correlated with LS aBMD in preadolescent individuals. BPN exposure also had a significant association with non‐aBMD clinical outcome variables. Logistic regression modeling predicted that with BPN exposure, a 1‐year increase in age would be associated with an 8.2% decrease in fracture probability for preadolescent individuals with OI‐1, compared with no decrease in individuals who had never received any BPN (p < 0.05). In preadolescent individuals with OI‐1, a 0.1 g/cm² increase in LS aBMD was associated with a 10.6% decrease in scoliosis probability, compared with a 46.8% increase in the BPN‐naïve group (p < 0.01). For the same changes in age and LS aBMD in preadolescent individuals, BPN exposure was also associated with higher mobility scores (p < 0.01), demonstrating that BPN treatment may be associated with daily function. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Management of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is the term used to describe a group of rare inherited skeletal disorders characterized by a greatly increased risk of fragility fractures (1). Mutations in several genes can cause OI but the condition is most commonly caused by mutations of COLIA1 or COL1A2 resulting in the production of collagen which is abnormal or present in reduced amounts. Fractures in OI are particularly common during childhood but the elevated fracture risk continues throughout life. Bone mineral density (BMD) can be reduced in OI but the magnitude of increase in fracture risk is far greater than can be accounted for by low BMD, highlighting that a key mechanism of bone fragility is reduced bone quality due to defects of bone matrix and mineralization. A multidisciplinary approach is needed to optimize management of OI, with input from physicians, orthopedic surgeons, physiotherapists, occupational therapists, and other allied health professionals. Orthopedic surgery plays a key role both in the fixation of fractures and in the correction of limb deformities. Bisphosphonates have been widely used in the treatment of children and adults with OI. Although there is good evidence that they increase BMD, it is uncertain to what extent they reduce fracture risk. Clinical trials of bone anabolic drugs such as teriparatide and inhibitors of sclerostin have also been studied; although they increase BMD, studies of these agents have not been powered to look at fracture endpoints. Various other treatment modalities including denosumab, and cell therapy have been explored but haven't gained acceptance in routine clinical practice. There have been huge advances in understanding the pathogenesis of OI but these have not been accompanied by advances in treatment. This signals need for well-designed clinical trials with fracture endpoints in OI, both with existing agents and with the newer therapeutic agents that are now starting to emerge.

New Insights Into Monogenic Causes of Osteoporosis

Osteoporosis, characterized by deteriorated bone microarchitecture and low bone mineral density, is a chronic skeletal disease with high worldwide prevalence. Osteoporosis related to aging is the most common form and causes significant morbidity and mortality. Rare, monogenic forms of osteoporosis have their onset usually in childhood or young adulthood and have specific phenotypic features and clinical course depending on the underlying cause. The most common form is osteogenesis imperfecta linked to mutations in COL1A1 and COL1A2, the two genes encoding type I collagen. However, in the past years, remarkable advancements in bone research have expanded our understanding of the intricacies behind bone metabolism and identified novel molecular mechanisms contributing to skeletal health and disease. Especially high-throughput sequencing techniques have made family-based studies an efficient way to identify single genes causative of rare monogenic forms of osteoporosis and these have yielded several novel genes that encode proteins partaking in type I collagen modification or regulating bone cell function directly. New forms of monogenic osteoporosis, such as autosomal dominant osteoporosis caused by WNT1 mutations or X-linked osteoporosis due to PLS3 mutations, have revealed previously unidentified bone-regulating proteins and clarified specific roles of bone cells, expanded our understanding of possible inheritance mechanisms and paces of disease progression, and highlighted the potential of monogenic bone diseases to extend beyond the skeletal tissue. The novel gene discoveries have introduced new challenges to the classification and diagnosis of monogenic osteoporosis, but also provided promising new molecular targets for development of pharmacotherapies. In this article we give an overview of the recent discoveries in the area of monogenic forms of osteoporosis, describing the key cellular mechanisms leading to skeletal fragility, the major recent research findings and the essential challenges and avenues in future diagnostics and treatments.

Pamidronate decreases bilirubin-impaired cell death and improves dentinogenic dysfunction of stem cells from human deciduous teeth

BACKGROUND

Hyperbilirubinemia that occurs in pediatric liver diseases such as biliary atresia can result in the development of not only jaundice in the brain, eyes, and skin, but also tooth abnormalities including green pigmentation and dentin hypoplasia in the developing teeth. However, hyperbilirubinemia-induced tooth impairments remain after liver transplantation. No effective dental management to prevent hyperbilirubinemia-induced tooth impairments has been established.

METHODS

In this study, we focused on pamidronate, which is used to treat pediatric osteopenia, and investigated its effects on hyperbilirubinemia-induced tooth impairments. We cultured stem cells from human exfoliated deciduous teeth (SHED) under high and low concentrations of unconjugated bilirubin in the presence or absence of pamidronate. We then analyzed the effects of pamidronate on the cell death, associated signal pathways, and dentinogenic function in SHED.

RESULTS

We demonstrated that a high concentration of unconjugated bilirubin induced cell death in SHED via the mitochondrial pathway, and this was associated with the suppression of AKT and extracellular signal-related kinase 1 and 2 (ERK1/2) signal pathways and activation of the nuclear factor kappa B (NF-κB) signal pathway. The high concentration of unconjugated bilirubin impaired the in vitro and in vivo dentinogenic capacity of SHED, but not the low concentration. We then demonstrated that pamidronate decreased the bilirubin-induced cell death in SHED via the altered AKT, ERK1/2, and NF-κB signal pathways and recovered the bilirubin-impaired dentinogenic function of SHED.

CONCLUSIONS

Our findings suggest that pamidronate may prevent tooth abnormalities in pediatric patients with hyperbilirubinemia.

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.

Atypical femur fracture in a woman with osteogenesis imperfecta and multiple myeloma

Use of intravenous bisphosphonates has been demonstrated to improve clinical outcomes in children with osteogenesis imperfecta (OI). However, efficacy and safety of bisphosphonates in adults with OI remains unclear. Atypical femur fractures (AFF) are rare insufficiency fractures associated with long-term bisphosphonate use. We report on a 56 year old woman with OI type 1 and long-term bisphosphonate use who was diagnosed with multiple myeloma (MM) following a severe vertebral fracture. During workup, an asymptomatic incomplete AFF of the left femur diaphysis was noted. Multiple factors may have contributed to the occurrence of AFF, including bisphosphonate exposure, bowing of the proximal femur, as well as the intrinsic collagen defect of OI. To reduce the risk of skeletal complications from MM, intravenous pamidronate was administered in addition to chemotherapy, though in reduced dose and frequency. Orthopedic consultant recommended against prophylactic surgery for the AFF. Follow-up radiograph showed no progression of the AFF, though delayed healing was present. This case highlights the importance of close monitoring of patients on long-term bisphosphonate therapy who have additional risk factors for developing AFF, such as underlying genetic bone disorders or lower limb deformities. A multidisciplinary approach is recommended for optimal management of such complex patients.

Novel compound heterozygous mutations in SERPINH1 cause rare autosomal recessive osteogenesis imperfecta type X

We identified novel compound heterozygous mutations in SERPINH1 in a Chinese boy suffering from recurrent fractures, femoral deformities, and growth retardation, which resulted in extremely rare autosomal recessive OI type X. Long-term treatment of BPs was effective in increasing BMD Z-score, reducing fracture incidence and reshaping vertebrae compression.

INTRODUCTION

Osteogenesis imperfecta (OI) is a heritable bone disorder characterized by low bone mineral density, recurrent fractures, and progressive bone deformities. Mutation in serpin peptidase inhibitor clade H, member 1 (SERPINH1), which encodes heat shock protein 47 (HSP47), leads to rare autosomal recessive OI type X. We aimed to detect the phenotype and the pathogenic mutation of OI type X in a boy from a non-consanguineous Chinese family.

METHODS

We investigated the pathogenic mutations and analyzed their relationship with the phenotype in the patient using next-generation sequencing (NGS) and Sanger sequencing. Moreover, the efficacy of long-term bisphosphonate treatment in this patient was evaluated.

RESULTS

The patient suffered from multiple fractures, low bone mass, and bone deformities in the femur, without dentinogenesis imperfecta or hearing loss. Compound heterozygous variants were found in SERPINH1 as follows: c.149 T>G in exon 2 and c.1214G>A in exon 5. His parents were heterozygous carriers of each of these mutations, respectively. Bisphosphonates could be helpful in increasing BMD Z-score, reducing bone fracture risk and reshaping the compressed vertebral bodies of this patient.

CONCLUSION

We reported novel compound heterozygous mutations in SERPINH1 in a Chinese OI patient for the first time, which expanded the spectrum of phenotype and genotype of extremely rare OI type X.

Pain and quality of life of children and adolescents with osteogenesis imperfecta over a bisphosphonate treatment cycle

The objective was to describe the pain and quality of life among children and adolescents with any osteogenesis imperfecta (OI) type over one intravenous bisphosphonate treatment cycle from a child and parental perspective. A prospective, observational study was conducted, where children and adolescents evaluated their pain intensity, location, and quality, as well as quality of life before, 1 week after treatment, and 6 months later. Quality of life was also evaluated from the parental perspective at the same three time points. Thirty-three child/parent dyads participated. The results showed that pain intensity on the 0-10 self-report scale after the Zoledronate infusion (median = 0, range = 0-6) was not different from pre (median = 2, range = 0-10) and 6-months post-scores (median = 2, range = 0-8) (p = 0.170). Children and adolescents with OI reported experiencing pain mainly in the ankles and the anterior and posterior shoulders. They selected evaluative pain descriptors such as uncomfortable (n = 16, 48%) and annoying (n = 13, 39%). Children and adolescents' functioning and quality of life did not change significantly across the bisphosphonate treatment cycle (p = 0.326), parents perceived an improvement immediately after the treatment compared to before (p = 0.016).

CONCLUSION

Children and adolescents with OI experience mild, yet complex pain localized across several body areas. There is little fluctuation in the pain intensity and functioning of children with OI undergoing bisphosphonate treatment. What is Known: • Acute and chronic musculoskeletal pain remains a major issue in OI. • Pain has a negative impact on quality of life. What is New: • New and unpublished methods and findings describing the pain and quality of life of children and adolescents with OI over one intravenous bisphosphonate treatment cycle from a child- and parental-proxy perspective. • Children and adolescents with OI experience pain intensity that is mild, yet complex in quality and localized across several body areas.

Adults with osteogenesis imperfecta: Clinical characteristics of 151 patients with a focus on bisphosphonate use and bone density measurements

An expert center for adults with Osteogenesis Imperfecta (OI) has been founded at the Isala Hospital in Zwolle, the Netherlands to achieve optimal care for adults with OI. Clinical data such as patient history, Dual Energy X-ray Absorptiometry measurements and laboratory findings are collected with patient consent. This study provides an overview of clinical characteristics of the patients who visited the clinic during its first 5 years, a total of 151 patients. In this study, we focus on bisphosphonate use and bone density measurements at time of presentation at the expert center. As such, insight into the natural history of OI in adults will be increased. Analysing the data of a large group of adults with this rare disorder within a national expert center will allow detailed exploration of the course of OI over time.

•

The reported cohort of 151 adult individuals with OI is one of the largest adult cohorts described in the literature.

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45/145 patients (31%) had a 25OH-vitamin D levels <50 nm/L. Only a small group reported calcium and vitamin D use.

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Men with OI type 1 aged <50 years had significantly lower Z-scores of the lumbar spine compared to women.

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T- and Z-scores were lower when measured at the LS compared to PF in type 1 and 4 OI patients.

•

BP use was variable; of OI type 1, 3 and 4 patients respectively 46.7%, 27.8% and 59.1% had never used BP.

Multiscale modeling of keratin, collagen, elastin and related human diseases: Perspectives from atomistic to coarse-grained molecular dynamics simulations

Scleroproteins are an important category of proteins within the human body that adopt filamentous, elongated conformations in contrast with typical globular proteins. These include keratin, collagen, and elastin, which often serve a common mechanical function in structural support of cells and tissues. Genetic mutations alter these proteins, disrupting their functions and causing diseases. Computational characterization of these mutations has proven to be extremely valuable in identifying the intricate structure-function relationships of scleroproteins from the molecular scale up, especially if combined with multiscale experimental analysis and the synthesis of model proteins to test specific structure-function relationships. In this work, we review numerous critical diseases that are related to keratin, collagen, and elastin, and through several case studies, we propose ways of extensively utilizing multiscale modeling, from atomistic to coarse-grained molecular dynamics simulations, to uncover the molecular origins for some of these diseases and to aid in the development of novel cures and therapies. As case studies, we examine the effects of the genetic disease Epidermolytic Hyperkeratosis (EHK) on the structure and aggregation of keratins 1 and 10; we propose models to understand the diseases of Osteogenesis Imperfecta (OI) and Alport syndrome (AS) that affect the mechanical and aggregation properties of collagen; and we develop atomistic molecular dynamics and elastic network models of elastin to determine the role of mutations in diseases such as Cutis Laxa and Supravalvular Aortic Stenosis on elastin's structure and molecular conformational motions and implications for assembly.

Inhibiting checkpoint kinase 1 protects bone from bone resorption by mammary tumor in a mouse model

DNA damage response plays a critical role in tumor growth, but little is known about its potential role in bone metabolism. We employed selective inhibitors of Chk1 and examined their effects on the proliferation and migration of mammary tumor cells as well as the development of osteoblasts and osteoclasts. Further, using a mouse model of bone metastasis we evaluated the effects of Chk1 inhibitors on bone quality. Chk1 inhibitors blocked the proliferation, survival, and migration of tumor cells in vitro and suppressed the development of bone-resorbing osteoclasts by downregulating NFATc1. In the mouse model, Chk1 inhibitor reduced osteolytic lesions and prevented mechanical weakening of the femur and tibia. Analysis of RNA-seq expression data indicated that the observed effects were mediated through the regulation of eukaryotic translation initiation factor 2 alpha, stress to the endoplasmic reticulum, S100 proteins, and bone remodeling-linked genes. Our findings suggest that targeting Chk1 signaling without adding DNA damaging agents may protect bone from degradation while suppressing tumor growth and migration.

Generalized metabolic bone disease and fracture risk in Rothmund-Thomson syndrome

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by poikiloderma, small stature, sparse hair, skeletal abnormalities, increased risk of osteosarcoma, and decreased bone mass. To date, there has not been a comprehensive evaluation of the prevalence and extent of metabolic bone disease in RTS. Furthermore, the mechanisms that result in this phenotype are largely unknown. In this report, we provide a detailed evaluation of 29 individuals with RTS with respect to their metabolic bone status including bone mineral density, calcium kinetics studies, and markers of bone remodeling. We show that individuals with RTS have decreased areal bone mineral density. Additionally, we demonstrate that the presence of pathogenic variants in RECQL4 and low bone mineral density correlate with the history of increased risk of fractures. Using a RECQL4-deficient mouse model that recapitulates skeletal abnormalities seen in individuals with RTS, we demonstrate that generalized skeletal involvement is likely due to decreased osteogenesis. Our findings are clinically relevant as they may help in the risk stratification of patients with RTS and also in the identification of individuals who may benefit from additional surveillance and management of metabolic bone disease.

Genetic Risk Factors for Atypical Femoral Fractures (AFFs): A Systematic Review

Atypical femoral fractures (AFFs) are uncommon and have been associated particularly with long‐term antiresorptive therapy, including bisphosphonates. Although the pathogenesis of AFFs is unknown, their identification in bisphosphonate‐naïve individuals and in monogenetic bone disorders has led to the hypothesis that genetic factors predispose to AFF. Our aim was to review and summarize the evidence for genetic factors in individuals with AFF. We conducted structured literature searches and hand‐searching of conference abstracts/reference lists for key words relating to AFF and identified 2566 citations. Two individuals independently reviewed citations for (i) cases of AFF in monogenetic bone diseases and (ii) genetic studies in individuals with AFF. AFFs were reported in 23 individuals with the following 7 monogenetic bone disorders (gene): osteogenesis imperfecta (COL1A1/COL1A2), pycnodysostosis (CTSK), hypophosphatasia (ALPL), X‐linked osteoporosis (PLS3), osteopetrosis, X‐linked hypophosphatemia (PHEX), and osteoporosis pseudoglioma syndrome (LRP5). In 8 cases (35%), the monogenetic bone disorder was uncovered after the AFF occurred. Cases of bisphosphonate‐naïve AFF were reported in pycnodysostosis, hypophosphatasia, osteopetrosis, X‐linked hypophosphatemia, and osteoporosis pseudoglioma syndrome. A pilot study in 13 AFF patients and 268 controls identified a greater number of rare variants in AFF cases using exon array analysis. A whole‐exome sequencing study in 3 sisters with AFFs showed, among 37 shared genetic variants, a p.Asp188Tyr mutation in the GGPS1 gene in the mevalonate pathway, critical to osteoclast function, which is also inhibited by bisphosphonates. Two studies completed targeted ALPL gene sequencing, an ALPL heterozygous mutation was found in 1 case of a cohort of 11 AFFs, whereas the second study comprising 10 AFF cases did not find mutations in ALPL. Targeted sequencing of ALPL, COL1A1, COL1A2, and SOX9 genes in 5 cases of AFF identified a variant in COL1A2 in 1 case. These findings suggest a genetic susceptibility for AFFs. A large multicenter collaborative study of well‐phenotyped AFF cases and controls is needed to understand the role of genetics in this uncommon condition. © 2017 The Authors JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Management of atypical femoral fracture in a patient with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a generalised connective tissue disorder associated with low bone mass, bone fragility and increased susceptibility to fractures. First-line treatment to improve bone mineral density (BMD) is usually with bisphosphonates but long-term usage has been associated with uncommon complications such as atypical femoral fractures (AFF). Treatment with teriparatide in this situation has been reported with positive outcomes. However, choice of treatment after 2 years of teriparatide has not been well studied or reported. We describe a patient with OI treated with bisphosphonates for 9 years, who then suffered a spontaneous AFF, was subsequently started on teriparatide for 2 years followed by 6 monthly Denosumab. 1 year post-treatment with Denosumab, there was significant improvement in BMD, good fracture healing and no new fractures. This case highlights the potential use of denosumab following 2 years of teriparatide treatment in patients with OI with AFF.

Osteogenesis Imperfecta

Osteogenesis imperfecta is a common heritable connective tissue disorder. Nearly ninety percent are due to Type I collagen mutations. Type I-IV are autosomal dominant, and Type VI-XIII are autosomal recessive. They are Graded 1-5 based on severity. Genomic testing is done by collagen analysis from fibroblasts. The mainstay of treatment is bisphosphonate therapy. The prognosis is variable.

Skeletal Dysplasias: What Every Bone Health Clinician Needs to Know

PURPOSE OF REVIEW

This review highlights how skeletal dysplasias are diagnosed and how our understanding of some of these conditions has now translated to treatment options.

RECENT FINDINGS

The use of multigene panels, using next-generation sequence technology, has improved our ability to quickly identify the genetic etiology, which can impact management. There are successes with the use of growth hormone in individuals with SHOX deficiencies, asfotase alfa in hypophosphatasia, and some promising data for c-type natriuretic peptide for those with achondroplasia. One needs to consider that a patient with short stature has a skeletal dysplasia as options for management may be available.

Splenomegaly, myeloid lineage expansion and increased osteoclastogenesis in osteogenesis imperfecta murine

Osteogenesis imperfecta (OI) is a disease caused by defects in type I collagen production that results in brittle bones. While the pathology is mainly caused by defects in the osteoblast lineage, there is also elevated bone resorption by osteoclasts resulting in high bone turnover in severe forms of the disease. Osteoclasts originate from hematopoietic myeloid cells, however changes in hematopoiesis have not been previously documented in OI. In this study, we evaluated hematopoietic lineage distribution and osteoclast progenitor cell frequency in bone marrow, spleen and peripheral blood of osteogenesis imperfecta murine (OIM) mice, a model of severe OI. We found splenomegaly in all ages examined, and expansion of myeloid lineage cells (CD11b⁺) in bone marrow and spleen of 7-9week old male OIM animals. OIM spleens also showed an increased frequency of purified osteoclast progenitors. This phenotype is suggestive of chronic inflammation. Isolated osteoclast precursors from both spleen and bone marrow formed osteoclasts more rapidly than wild-type controls. We found that serum TNFα levels were increased in OIM, as was IL1α in OIM females. We targeted inflammation therapeutically by treating growing animals with murine TNFR2:Fc, a compound that blocks TNFα activity. Anti-TNFα treatment marginally decreased spleen mass in OIM females, but failed to reduce bone resorption, or improve bone parameters or fracture rate in OIM animals. We have demonstrated that OIM mice have changes in their hematopoietic system, and form osteoclasts more rapidly even in the absence of OI osteoblast signals, however therapy targeting TNFα did not improve disease parameters.

Long-Term Bisphosphonate Therapy in Osteogenesis Imperfecta

PURPOSE OF REVIEW

Osteogenesis imperfecta (OI) is a genetic bone disorder resulting in bone fragility. It has a heterogeneous phenotype which typically includes reduced bone mass, multiple fractures, deformity, and chronic disability. Bisphosphonate treatment remains the first-line medical management, but there is still debate on aspects of its effectiveness. This review summarizes current knowledge about long-term bisphosphonate use in OI with recommendations on clinical application.

RECENT FINDINGS

Bisphosphonates increase bone mineral density, most notably of the vertebrae, and reduce fracture risk in the pediatric OI population. Gains in strength and mobility, together with the permissive effect on orthopedic surgery (e.g., in combination with intramedullary rodding) and physiotherapy, have resulted in improved quality of life for those with OI. As experience in its use continues, the risks and benefits of long-term bisphosphonate treatment in OI are slowly emerging. Patient registries containing data on genotype, phenotype, fractures, bisphosphonate treatment, orthopedic intervention, and functional outcomes are essential for systematic evaluation given the lack of large multi-centered randomized control trials.

A novel large fragment deletion in PLS3 causes rare X-linked early-onset osteoporosis and response to zoledronic acid

We identified a novel large fragment deletion from intron 9 to 3'UTR in PLS3 (E10-E16del) in one Chinese boy with X-linked early-onset osteoporosis and vertebral fractures, which expanded the pathogenic spectrum of X-linked early-onset osteoporosis. Treatment with zoledronic acid was beneficial for increasing BMD and reshaping the vertebral bodies of this patient.

INTRODUCTION

X-linked early-onset osteoporosis is a rare disease, which is characterized by low bone mineral density (BMD), vertebral compression fractures (VCFs), and/or long bone fractures. We aimed to detect the phenotype and the underlying pathogenic mutation of X-linked early-onset osteoporosis in a boy from a nonconsanguineous Chinese family.

METHODS

We investigated the pathogenic mutation of the patient with X-linked early-onset osteoporosis by targeted next-generation sequencing and confirmed it by Sanger sequencing. We also observed the effects of zoledronic acid on fracture frequency and BMD of the patient.

RESULTS

Low BMD and multiple VCFs were the main phenotypes of X-linked early-onset osteoporosis. We identified a total of 12,229 bp deletion in PLS3, involving intron 9 to the 3'UTR (E10-E16 del). This large fragment deletion might be mediated by Alu repeats and microhomology of 26 bp at each breakpoint junction. Zoledronic acid treatment could significantly increase the Z-score of BMD and reshape the compressed vertebral bodies.

CONCLUSION

We identified a large fragment deletion mutation in PLS3 for the first time and elucidated the possible mechanism of the deletion, which led to X-linked early-onset osteoporosis and multiple vertebral fractures. Our findings would enrich the etiology spectrum of this rare disease.