Osteogenesis imperfecta in children and adolescents-new developments in diagnosis and treatment

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.

Predicting ambulatory function at skeletal maturity in children with moderate to severe osteogenesis imperfecta

Maximizing ambulation is a key treatment aim in moderate to severe osteogenesis imperfecta (OI). Here we investigated which early clinical characteristics predicted ambulation function at skeletal maturity. We assessed Bleck ambulation scores in 88 individuals with OI at 5 to 6 years of age and again at final height (at 15 to 24 years of age). At 5 to 6 years of age, 33 (38%) children were non-ambulators, 32 (36%) were fully independent ambulators, and 23 (26%) had intermediate ambulation skills. At skeletal maturity, 58% of the study participants had the same mobility level as at first assessment. The ability to ambulate independently at skeletal maturity was predicted by independent ambulation at 5 to 6 years (odds ratio [OR] 22.6, 95% confidence interval [CI] 4.9-105; P < 0.001), height z score at 5 to 6 years (OR 3.1, CI 1.6-6.3; P = 0.001) and weight z score at 5 to 6 years (OR 0.44, CI 0.19-0.99; P = 0.04).Conclusion: Independent ambulation at 5 to 6 years was the main determinant of independent ambulation at skeletal maturity. This highlights the importance of maximizing ambulation in children below 5 years of age. What is Known: •walking ability varies markedly between OI types. The highest level of mobility was found in OI type I, the lowest in OI type III who require mobility aids; intermediate levels were reported for OI type IV. • OI type is a key predictor of ultimate ability to ambulate, whereas the timing of developmental milestones was not associated with walking ability What is New: • overall key predictors of mobility function at skeletal maturity were mobility status and height z-score at 5-6 years of age • Childrenwho were non-ambulators at 5 to 6 years of age had a higher chance of having better mobility at skeletal maturity if they had good upper extremity function, as expressed in the PEDI Self Care Score.

Neonatal Bone Disorders

Neonatologists care for newborns with either an antenatal suspicion or postnatal diagnosis of bone disease. With improved ultrasound imaging techniques, more cases of neonatal bone disorders are identified antenatally and this requires further diagnostic/molecular testing either antenatally or soon after birth for confirmation of the diagnosis and facilitating subsequent management. Prompt diagnosis is vital in certain conditions where initiation of treatment is time critical and life saving. We outline an approach to diagnosis, investigation, and management of a neonate with a suspected bone disorder.

Glucocorticoid-Induced Osteoporosis: Why Kids Are Different

Glucocorticoids (GC) are an important risk factor for bone fragility in children with serious illnesses, largely due to their direct adverse effects on skeletal metabolism. To better appreciate the natural history of fractures in this setting, over a decade ago the Canadian STeroid-associated Osteoporosis in the Pediatric Population ("STOPP") Consortium launched a 6 year, multi-center observational cohort study in GC-treated children. This study unveiled numerous key clinical-biological principles about GC-induced osteoporosis (GIO), many of which are unique to the growing skeleton. This was important, because most GIO recommendations to date have been guided by adult studies, and therefore do not acknowledge the pediatric-specific principles that inform monitoring, diagnosis and treatment strategies in the young. Some of the most informative observations from the STOPP study were that vertebral fractures are the hallmark of pediatric GIO, they occur early in the GC treatment course, and they are frequently asymptomatic (thereby undetected in the absence of routine monitoring). At the same time, some children have the unique, growth-mediated ability to restore normal vertebral body dimensions following vertebral fractures. This is an important index of recovery, since spontaneous vertebral body reshaping may preclude the need for osteoporosis therapy. Furthermore, we now better understand that children with poor growth, older children with less residual growth potential, and children with ongoing bone health threats have less potential for vertebral body reshaping following spine fractures, which can result in permanent vertebral deformity if treatment is not initiated in a timely fashion. Therefore, pediatric GIO management is now predicated upon early identification of vertebral fractures in those at risk, and timely intervention when there is limited potential for spontaneous recovery. A single, low-trauma long bone fracture can also signal an osteoporotic event, and a need for treatment. Intravenous bisphosphonates are currently the recommended therapy for pediatric GC-induced bone fragility, typically prescribed to children with limited potential for medication-unassisted recovery. It is recognized, however, that even early identification of bone fragility, combined with timely introduction of intravenous bisphosphonate therapy, may not completely rescue the osteoporosis in those with the most aggressive forms, opening the door to novel strategies.

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.

Assessment of longitudinal bone growth in osteogenesis imperfecta using metacarpophalangeal pattern profiles

OBJECTIVE

Osteogenesis imperfecta (OI) is commonly associated with short stature, but it is unclear whether this is exclusively secondary to fractures and bone deformities or whether there is a primary defect in longitudinal bone growth. As metacarpal and phalangeal bones are rarely affected by fractures and deformities, any length deficits in these bones should reflect a direct disease effect on longitudinal growth. This study therefore assessed the relationship of hand bone length with clinical OI type and genotype.

STUDY DESIGN

Prospective study.

RESULTS

The length of all 19 tubular hand bones were measured in 144 individuals (age 6 to 57 years; 68 female) who had OI caused by COL1A1 or COL1A2 variants. Measurements of bone length were converted to z-scores using published reference data. Bone length was mostly normal in OI type I but was significantly decreased in OI types III and IV. Mean hand bone length z-score (i.e., the average length z-score of all 19 bones of a hand) was -0.2 for OI type I, -2.9 for OI type III and -1.2 for OI type IV. Mean hand bone length z-score was positively associated with height z-score (r² = 0.65, P < 0.001). Regarding genotype-phenotype correlations, mean hand bone length z-score was close to 0 in individuals with COL1A1 mutations leading to haploinsufficiency but were significantly lower in the presence of mutations leading to triple-helical glycine substitutions in either the alpha 1 or alpha 2 chain of collagen type I.

CONCLUSION

COL1A1 and COL1A2 mutations affect bone growth not only by inducing fractures and bone deformities, but also through longitudinal growth deficits in bones that do not fracture or deform.

Giving Children With Osteogenesis Imperfecta a Voice: Participatory Approach for the Development of the Interactive Assessment and Communication Tool Sisom OI

BACKGROUND

Children with osteogenesis imperfecta (OI) experience acute and chronic symptoms that expose them to physical, mental, and social challenges. Empowering these children by involving them in their care can help them to cope with OI. Sisom is an interactive assessment and communication tool designed to help children aged 6-12 years with chronic illnesses express their symptoms. This tool has not yet been adapted to the unique needs of OI.

OBJECTIVE

The aim of this study was to develop a Sisom OI paper prototype by seeking the perspectives of end users.

METHODS

A participatory approach was adopted to develop the prototype overseen by an expert panel of 9 clinicians at a university-affiliated pediatric hospital. Purposive sampling was used to recruit 12 children with OI who were aged 6-12 years. The study was carried out over the course of 3 feedback cycles. Data were deductively interpreted using content analysis techniques.

RESULTS

Overall, 64% (57/89) of the Sisom symptoms were deemed relevant for inclusion in Sisom OI, with 42% (37/89) directly incorporated and 22% (20/89) incorporated with changes. In total, 114 symptoms were used to create the prototype, of which 57 were newly generated. The relevant symptoms addressed children's thoughts and feelings about hospitalization and their wishes for participation in their own care. The new symptoms addressed fractures, body image, and social isolation related to difficulties with accessibility and intimidation.

CONCLUSIONS

Once developed, Sisom OI will offer clinicians an innovative and child-centered approach to capture children's perspectives on their condition.

Guidelines for the management of children at risk of secondary bone fragility: Expert opinion of a French working group

The current French national guidelines were elaborated by a working group consisting of experts in the field of pediatric endocrinology, rheumatology, hepatogastroenterology, nephrology, and pneumology. A systematic search was undertaken of the literature published between 2008 and 2018 and indexed in PubMed. The recommendations developed were then validated by an external evaluation group comprising representatives from the various highly specialized fields in pediatrics, representatives of the societies and groups supporting the development of the guidelines, and representatives of different healthcare professions. The objective of these guidelines was to detail the current optimal management of children at risk of secondary bone fragility.

The molecular landscape of osteogenesis imperfecta in a Brazilian tertiary service cohort

We have sought the molecular diagnosis of OI in 38 Brazilian cases through targeted sequencing of 15 candidate genes. While 71% had type 1 collagen-related OI, defects in FKBP10, PLOD2 and SERPINF1, and a potential digenic P3H1/WNT1 interaction were prominent causes of OI in this underrepresented population.

INTRODUCTION

Defects in type 1 collagen reportedly account for 85-90% of osteogenesis imperfecta (OI) cases, but most available molecular data has derived from Sanger sequencing-based approaches in developed countries. Massively parallel sequencing (MPS) allows for systematic and comprehensive analysis of OI genes simultaneously. Our objective was to obtain the molecular diagnosis of OI in a single Brazilian tertiary center cohort.

METHODS

Forty-nine individuals (84% adults) with a clinical diagnosis of OI, corresponding to 30 sporadic and 8 familial cases, were studied. Sixty-three percent had moderate to severe OI, and consanguinity was common (26%). Coding regions and 25-bp boundaries of 15 OI genes (COL1A1, COL1A2, IFITM5 [plus 5'UTR], SERPINF1, CRTAP, P3H1, PPIB, SERPINH1, FKBP10, PLOD2, BMP1, SP7, TMEM38B, WNT1, CREB3L1) were analyzed by targeted MPS and variants of interest were confirmed by Sanger sequencing or SNP array.

RESULTS

A molecular diagnosis was obtained in 97% of cases. COL1A1/COL1A2 variants were identified in 71%, whereas 26% had variants in other genes, predominantly FKBP10, PLOD2, and SERPINF1. A potential digenic interaction involving P3H1 and WNT1 was identified in one case. Phenotypic variability with collagen defects could not be explained by evident modifying variants. Four consanguineous cases were associated to heterozygous COL1A1/COL1A2 variants, and two nonconsanguineous cases had compound PLOD2 heterozygosity.

CONCLUSIONS

Novel disease-causing variants were identified in 29%, and a higher proportion of non-collagen defects was seen. Obtaining a precise diagnosis of OI in underrepresented populations allows expanding our understanding of its molecular landscape, potentially leading to improved personalized care in the future.

Musculoskeletal phenotype in two unrelated individuals with a recurrent nonsense variant in SGMS2

Heterozygous mutations in the gene encoding the sphingomyelin synthase 2, SGMS2, have recently been linked to childhood-onset osteoporosis and skeletal dysplasia. One nonsense variant at position c.148C>T (p.Arg50*) has been associated with mild bone fragility with or without cranial sclerosis. Here we assessed the effect of the SGMS2 p.Arg50* variant in two unrelated probands with childhood-onset osteoporosis and their unaffected family members. We found that the p.Arg50* variant was associated with phenotypic variability, ranging from absence of a bone phenotype to severe vertebral compression fractures and low lumbar spine areal bone mineral density (BMD) as measured by dual energy x-ray absorptiometry. Peripheral quantitative computed tomography of the radius and tibia in the two probands revealed low cortical volumetric BMD and reduced cortical thickness. In addition, both probands were obese and suffered from muscle function deficits compared to sex- and age-matched controls. Long-term bisphosphonate treatment was associated with reshaping of previously compressed vertebral bodies.

Exploring the Perceived Self-management Needs of Young Adults With Osteogenesis Imperfecta

PURPOSE

To explore the perceived self-management needs of young adults with osteogenesis imperfecta (OI) with the goal of optimizing the self-management and transitional care services.

METHODS

A qualitative descriptive study was performed with young adults diagnosed with OI. Two semistructured interviews were conducted before and after their first appointment with a nurse practitioner in the adult healthcare settings (a new partnership initiated by the pediatric hospital). Data were transcribed and descriptively analyzed.

RESULTS

Seven participants with OI types I, III, and IV were interviewed. Ages ranged from 23 to 34 years, and years since discharge from the pediatric hospital ranged from 3 to 10. Four themes emerged including (1) dropped in the jungle, with no one to call; (2) they do not know how to treat me; (3) I feel like I'm going to get back in the loop; and (4) self-managing what I know, how I know.

CONCLUSIONS

Similar to other childhood-onset conditions, adolescents and young adults with OI require education and mentorship, and clinicians in the adult healthcare system need to be prepared and supported to receive them. Collective efforts are needed to improve the self-management and transitional care needs for young adults with OI.

Bone Disease in Patients with Ehlers-Danlos Syndromes

PURPOSE OF REVIEW

To summarize the bone findings, mainly bone mass and fracture risk, in Ehlers-Danlos syndromes (EDS).

RECENT FINDINGS

Low bone mineral density and fractures seem to be frequent in some of the rare EDS types (kyphoscoliotic, arthrochalasia, spondylodysplastic, and classic-like EDS). For the more prevalent hypermobile and classic EDS types, some case-control studies found mildly decreased bone mineral density, but it was not clear that fracture rates were increased. Nevertheless, abnormalities in vertebral shape seem to be common in classical and hypermobile EDS types. In a cohort of individuals with EDS followed since birth, no fractures were observed during infancy. Bone mineral density varies widely among the different types of EDS, and vertebral abnormalities seem to be common in classical and hypermobile EDS. It might be justified to perform spine radiographs and bone mineral density assessments in newly diagnosed EDS.

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.

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.

Exploring the Views of Osteogenesis Imperfecta Caregivers on Internet-Based Technologies: Qualitative Descriptive Study

Background

Osteogenesis imperfecta (OI) is a rare genetic condition that can lead to frequent debilitating bone fractures. Family caregivers of children with OI face unique challenges in providing care, which may include limited access to information about the condition, feelings of distress, and experiences of social isolation. Internet-based technologies (IBTs) have been useful for supporting other types of caregivers. However, the views of OI caregivers on IBTs have not been explored.

Objective

This study aimed to explore the views of OI caregivers on the uses of IBTs to support them in caring for their children with OI.

Methods

A qualitative descriptive study was conducted. Caregivers of children with OI were recruited at a pediatric hospital in Montreal, Canada. Interviews were used to explore each caregiver’s views on the applicability of IBTs in supporting their caregiving needs. The interviews were transcribed verbatim and thematically analyzed.

Results

A total of 18 caregivers participated. The caregivers shared that IBTs were useful for facilitating the following activities: daily activities of caregiving (such as providing physical care, supporting relationships, supporting self-care and hope, and managing the logistics of caregiving), OI medical information seeking, and OI social networking. However, they also revealed concerns about the health consequences of IBT use and the quality of IBT content. Concerns regarding IBTs varied somewhat with caregivers’ geographies. Caregivers offered suggestions and strategies for how IBTs can be optimized for caregiving.

Conclusions

Family caregivers of children with OI face unique challenges in providing care, which may include lacking access to information about the rare condition and feeling socially isolated. OI caregivers use IBTs to overcome some of these challenges and to support their specific caregiving needs. These findings contribute to the paucity of knowledge by offering varied IBT strategies to support caregiving activities, which may be beneficial for other caregivers. Participants’ suggestions for IBT services can inform the development of new resources for OI caregivers and potentially for other caregivers of children living with rare conditions.

A novel Ser40Trp variant in IFITM5 in a family with osteogenesis imperfecta and review of the literature

Osteogenesis imperfecta, is a genetically and clinically heterogeneous connective tissue disorder that disrupts bone architecture, making it fragile and more prone to fractures. While more than 85% of cases are due to variants in COL1A1 and COL1A2, variants in noncollagen genes have been identified in the remaining cases. The recurring heterozygous variant in IFITM5 (c.-14C>T) leads to osteogenesis imperfecta type V, a second missense variant in IFITM5 (c.119C>T, p.Ser40Leu) leads to phenotype resembling osteogenesis imperfecta type VI. In this report, we describe the first patient with Ser40Trp variant in IFITM5, who presented with multiple fractures in the prenatal period. She remained fracture free after birth (except for trauma-related fractures during puberty) with normal bone mineral densitometry. Her mother, who did not have a history of fracture, was noted to have somatogonadal mosaicism for this variant and became pregnant with a second child with multiple prenatal fractures, found to have the same variant. To our knowledge, this is the first case of somatogonadal mosaicism in IFITM5. In addition, we have summarized the literature on patients presenting with variant in codon 40 (serine) of IFTIM5 protein.

Osteogenesis Imperfecta: Skeletal Outcomes After Bisphosphonate Discontinuation at Final Height

Intravenous cyclical bisphosphonates are widely used to treat children with moderate to severe osteogenesis imperfecta (OI). Bisphosphonates are often discontinued when growth is completed, but subsequent skeletal changes have not been studied in detail. We assessed 31 patients (22 females) with OI who had started intravenous bisphosphonates (either pamidronate or zoledronic acid) before 13 years of age, were treated for at least 2 years (range 4.7-15.7 years), and discontinued treatment after completion of growth, when their age ranged from 13.4 to 20.0 years (mean 16.4 years). At 4 years after treatment discontinuation, lumbar spine areal bone mineral density (BMD) had increased by 4% (p < 0.05). Peripheral quantitative computed tomography of the radius showed a decrease in trabecular volumetric BMD at the distal metaphysis of 19% but an increase in cortical volumetric BMD of 4% (p < 0.05 for both). None of the patients sustained a new vertebral compression fracture during follow-up. The proportion of patients with new long-bone fractures was higher in the 2 years before treatment discontinuation than in the last 2 years of follow-up (42% and 16%, respectively; p < 0.05). © 2019 American Society for Bone and Mineral Research.

Effects of zoledronic acid on vertebral shape of children and adolescents with osteogenesis imperfecta

Vertebral compression fracture (VCF) is a common and severe complication of osteogenesis imperfecta (OI). We prospectively observe the changes of vertebral shape during zoledronic acid (ZOL) treatment and assess influence factors of VCF in OI children. 32 children with VCF and 10 children without VCF (NVCF) were included and given ZOL treatment for 2 years, who were matched in age and gender. Control group included 17 treatment naïve OI patients with VCF who were matched in age, gender and clinical severity to 17 patients in VCF group received ZOL treatment for 1 year (as ZOL treated group). We performed quantitative vertebral morphometry and calculated concavity index (mh/ph), height-length ratio (ah/LL, mh/LL, ph/LL) and projection area (PA) of vertebrae from T4 to L4 before and after treatment. At baseline, patients in VCF group had significantly lower PA, mh/ph, ah/LL, mh/LL and ph/LL than patients in NVCF group (P < 0.01). PA, mh/ph, ah/LL, mh/ LL and ph/LL of patients with VCF were raised by (35.2 ± 19.5)%, (22.9 ± 15.1)%, (19.6 ± 13.9)%, (33.6 ± 25.5)%, and (8.1 ± 8.8)% (P < 0.01) after 1-year treatment of ZOL, and were increased by (71.8 ± 28.2)%, (42.8 ± 21.8)%, (35.1 ± 20.6)%, (65.4 ± 43.2)%, and (12.5 ± 11.4)% after 2-year treatment of ZOL (P < 0.01). Compared to control group, mh/ph, ah/LL and mh/LL were significantly higher (P < 0.01) in ZOL treated group. LS-BMD and its increase were positively correlated to vertebral height and PA at baseline and the improvement of vertebral height and PA after ZOL treatment, respectively. In conclusion, the compressive vertebrae of OI children could be effectively reshaped during ZOL treatment. Low LS-BMD was an independent risk factor for VCF and its increase was positively correlated to the improvement in vertebral shape after ZOL treatment.

Mendelian bone fragility disorders

Mendelian bone fragility disorders are caused by genetic variants that can be inherited in an autosomal dominant, autosomal recessive or X-linked manner and have a large detrimental effect on bone strength. As a rule, the more damaging the genetic defect is, the earlier the first fracture will occur, typically during bone development. This review focusses on conditions where bone fragility is the most conspicuous characteristic, of which osteogenesis imperfecta (OI) is the best-known disorder. The large majority of individuals with an OI phenotype have disease-causing dominant variants in COL1A1 or COL1A2, the genes coding for collagen type I. Interestingly, large sequencing databases indicate that there are about 10 times more carriers of COL1A1/COL1A2 variants that should lead to OI than there are individuals with a diagnosis of OI. It is possible that at least some of these variants lead to incomplete OI phenotypes and are diagnosed as osteoporosis during adulthood. Apart from mutations affecting collagen type I production, biallelic mutations in LRP5 and WNT1 can cause very rare and severe bone fragility disorders. Heterozygous pathogenic variants in these genes are much more common and can cause the clinical picture of primary osteoporosis. As sequencing studies are more widely performed in adults with bone fragility disorders, evidence is emerging that what appears as primary osteoporosis in fact can be due to mutations in bona fide OI genes. The distinction between OI and primary osteoporosis is therefore likely to blur in future.

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.

Cone-Beam Computed Tomography of Osteogenesis Imperfecta Types III and IV: Three-Dimensional Evaluation of Craniofacial Features and Upper Airways

This cross-sectional study investigated the natural history of craniofacial deformities in osteogenesis imperfecta (OI) and determined the impact of three-dimensional (3D) analysis on diagnosis and treatment planning in orthodontics and orthognathic surgery in comparison to conventional two-dimensional (2D) cephalometric examination. 3D images of the craniofacial complex were acquired during 1 calendar year using cone-beam computed tomography (CBCT) from a cohort of 41 individuals (aged 11 to 35 years; 28 females) with OI type III (n = 13) or IV (n = 28). 3D evaluation of the craniocervical junction and upper airways was conducted using InVivoTM. 2D lateral cephalogram was constructed, traced, and examined using the University of Western Ontario analysis (DolphinTM). Quantitative and qualitative parameters were compared between OI type III and type IV groups (unpaired t test) and the unaffected population (Z-score). 3D evaluation revealed a high prevalence of craniocervical abnormalities, craniofacial asymmetries, and nasal septum deviation in both OI groups. Mean airway dimensions were comparable to the non-affected population norms, except for 5 individuals who had insufficient airway dimensions. In 2D, the maxilla was retrognathic and hypoplastic, and the mandibular position was convergent with respect to the face, resulting in mandibular prognathism and face height reduction. The 2D trends were more pronounced in OI type III, whereas the 3D craniocervical and airway abnormalities were common in both types. This study illustrates the prevalence of craniofacial and airway anomalies in OI that occur along with facial deformities are not associated with postcranial phenotype and OI type, are apparent only in 3D evaluation, and are likely to influence treatment strategy. For OI patients, a team effort involving a dentist, orthodontist, neurologist, and ear-nose-throat (ENT) practitioner is recommended for successful management of craniofacial deformities.

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.

A novel missense mutation in P4HB causes mild osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a rare heritable bone disorder characterized by low bone mineral density (BMD), recurrent bone fractures, and progressive bone deformities. P4HB encodes protein disulfide isomerase (PDI) and is identified as a novel candidate gene of OI. The purposes of the present study are to detect pathogenic mutation, to evaluate the phenotypes of a Chinese family with mild OI, and to investigate the effects of bisphosphonates on bone of the proband. We detected the pathogenic mutation by next generation sequencing and Sanger sequencing. Laboratory and radiological investigations were conducted to evaluate the phenotypes. The proband was a 12-year-old girl with low BMD, history of recurrent non-traumatic fractures, slight scoliosis, with bluish grey sclera and ligamentous laxity. Her father suffered from one fragility fracture and slight wedge changes of vertebras, with bluish grey sclera. We identified a novel heterozygous missense mutation (c.692A>C, p.His231Pro) in P4HB in the proband and her father. This mutation was predicted to affect the combination of PDI with type I procollagen and lead to the disorder of its triple helix formation. Bisphosphonates were effective in reducing bone resorption and increasing BMD of the proband with well tolerance. In conclusion, we identified a novel mutation in P4HB in a Chinese family with mild OI, which expanded the genotypic and phenotypic spectrum of OI. Bisphosphonates were effective to this extremely rare OI induced by P4HB mutation.

Outcomes following intravenous bisphosphonate infusion in pediatric patients: A 7-year retrospective chart review

INTRODUCTION

Intravenous bisphosphonates (IV BP) have been used to treat children with osteoporosis for many years. Favorable side effect profile and improvements in bone mineral density (BMD) have been demonstrated in patients with osteogenesis imperfecta (OI), a primary form of osteoporosis in pediatrics. Less is known about the safety of IV BP in children with secondary osteoporosis or glucocorticoid-induced osteoporosis (GIO). We aimed to determine the prevalence of both acute and long-term side effects and assess the efficacy of IV BP treatment to increase bone mineral density in pediatric patients with varying presentations of compromised bone health.

METHODS

We conducted a retrospective chart review of pediatric patients (<21 years old) treated for osteoporosis with intravenous pamidronate (PAM) or zoledronic acid (ZA) at Cincinnati Children's Hospital Medical Center from 2010 to 2017. Patient demographics, diagnosis, infusion type and dose, acute phase reactions (APR), electrolyte abnormalities, and bone density measurements were collected from the electronic medical records. Diagnoses were grouped into 3 categories: primary osteoporosis, secondary osteoporosis, and GIO. Descriptive characteristics and adverse events were compared among categories. Change in bone mineral density (BMD) over time was compared among groups.

RESULTS

123 patients (56% male) received 942 infusions (83% PAM and 17% ZA). APR was reported in 7% of all infusions and more common in secondary osteoporosis (16%, p < 0.0001). There was a higher percentage of acute adverse events after the first infusion (27% vs 5%, p < 0.0001). Hypocalcemia following IV BP infusions occurred in 7% (27/379) of infusions and was significantly associated with ZA use (p = 0.04). Severity of hypocalcemia was generally mild, requiring intravenous calcium in 3% (13/379) of infusions. Hypophosphatemia occurred frequently, however rarely required intravenous supplementation. In 468 patient years of IV BP exposure, there were no reports of osteonecrosis of the jaw (ONJ) nor atypical femoral fracture (AFF). Lumbar spine (LS) aBMD Z-score 1 year after IV BP initiation increased overall for all groups (p < 0.0001) but did not significantly differ for those who did or did not fracture following IV BP treatment.

CONCLUSIONS

APR due to intravenous BP treatment for pediatric osteoporosis were infrequent and generally mild. APR were more likely to occur in patients with secondary osteoporosis, a group who may require closer monitoring. A higher proportion of hypophosphatemia occurred in the patients with GIO. Long-term serious adverse events including ONJ and AFF were not identified in our patient population. LS aBMD Z-score increased following initiation of IV BP. However, the change in BMD was not associated with risk of fracture during the follow-up interval. These data provide reassurance and suggest that IV BP can be safely used in pediatric patients with osteoporosis.

Challenges of delivery of dental care and dental pathologies in children and young people with osteogenesis imperfecta

BACKGROUND

Osteogenesis imperfecta (OI) is the most common inherited disorder of bone fragility in children, increasing fracture risk 100-fold and can feature dental and facial bone involvement causing additional morbidities.

AIM

To assess the utilisation of tertiary dental services by children and young people with OI attending a supra-regional multi-disciplinary OI service and review of the pathology identified and interventions undertaken.

DESIGN

Case notes review of the current caseload of children and young people (0-18 years) with OI at a large regional OI specialist centre (n = 92). Primary outcome was whether an initial dental assessment was arranged in a tertiary dental centre and the corresponding attendance.

RESULTS

49% had a tertiary dental assessment arranged, of whom 82% attended (one quarter requiring several appointments) and 18% did not attend (DNA).Those travelling > 100 miles had a DNA rate of 47%. Assessed children had dentinogenesis imperfecta (24%, 50% in Type III OI), radiographs (95%), caries (41%), required extraction under general anaesthesia (38%) and malocclusion (30%). 48% of the total cohort received bisphosphonates.

CONCLUSION

Tertiary dental assessment encountered barriers to uptake of recommended referral in all patients, often due to geographic factors of travel distance, yet when implemented did identify pathology in a large proportion and many resulted in dental intervention. These emphasise the relevance of specialist dental assessment in OI, particularly in the modern context of increased use of bisphosphonates. This is challenging to achieve and several models of delivery of care may need to be considered in this chronic childhood condition.

The Bone Phenotype and Pain Response to Pamidronate in Tyrosine Kinase Inhibitor-Treated Chronic Myelogenous Leukemia

Tyrosine kinase inhibitors (TKIs) have been linked to bone pain and linear growth attenuation in children with TKI-treated chronic myelogenous leukemia (CML). We describe the skeletal phenotype in an 11-year-old boy with chronic bone pain due to TKI-treated CML, including his response to intravenous (IV) pamidronate. This boy was diagnosed with Philadelphia chromosome-positive CML at 4 years of age. He was treated with imatinib for 3 years, followed by dasatinib for 4 years. At age 11 years, he was seen in a bone health clinic with a 4-year history of leg pains that necessitated regular nonsteroidal anti-inflammatory drugs (NSAIDS) and downward crossing of height percentiles (from the 25th to fifth). The bone volume/tissue volume Z-score was +1.6 for a trans-iliac bone biopsy specimen, with an increase in trabecular number (Z-score, +3.1). Bone formation and resorption parameters on trabecular surfaces were within normal limits. Tibia volumetric bone mineral density (BMD) and bone geometry were normal by peripheral quantitative computed tomography, areal BMD Z-scores were average or above average at multiple skeletal sites by dual-energy x-ray absorptiometry, and tibia length Z-score was reduced (−2.3). Growth- and bone-related biochemical studies were unremarkable except a low serum alkaline phosphatase level. His bone pain resolved completely after 9 months of low-dose IV pamidronate. An increase in trans-iliac trabecular number and shortened tibia were the main skeletal features in this patient. Short-term IV pamidronate was effective for mitigating bone pain, allowing this boy to continue receiving dasatinib without the need for chronic NSAID therapy.

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

Caries prevalence and experience in individuals with osteogenesis imperfecta: A cross-sectional multicenter study

OBJECTIVE

Dentinogenesis Imperfecta (DI) forms a group of dental abnormalities frequently found associated with Osteogenesis Imperfecta (OI), a hereditary disease characterized by bone fragility. The objectives of this study were to quantify the dental caries prevalence and experience among different OI-types in the sample population and quantify how much these values change for the subset with DI.

METHODS

To determine which clinical characteristics were associated with increased Caries Prevalence and Experience (CPE) in patients with OI, the adjusted DFT scores were used to account for frequent hypodontia, impacted teeth and retained teeth in OI population. For each variable measured, frequency distributions, means, proportions and standard deviations were generated. Groups means were analyzed by the unpaired t-test or ANOVA as appropriate. For multivariate analysis, subjects with caries experience of zero were compared with those with caries experience greater than zero using logistic regression.

RESULTS

The stepwise regression analysis while controlling for all other variables demonstrated the presence of DI (OR 2.43; CI 1.37-4.32; P = 0.002) as the significant independent predictor of CPE in the final model.

CONCLUSION

This study found no evidence that CPE of OI subjects differs between the types of OI. The presence of DI when controlled for other factors was found to be the significant predictor of CPE.

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.

Kinetic and Kinematic Analysis of Gait in Type IV Osteogenesis Imperfecta Patients: A Comparative Study

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic connective tissue disorder characterized by skeletal deformity and increased risk of fracture. Independent mobility is of concern for OI patients as it is associated with the quality of life. The present study investigates the variation of kinetic and kinematic gait parameters of type IV OI subjects and compares them with age-matched healthy subjects.

MATERIALS AND METHODS

Gait analysis is performed on five type IV OI patients and six age-matched normal subjects. Spatiotemporal, kinematic, and kinetic data are obtained using Helen Hayes marker placement protocol.

RESULTS

The results indicate an imprecise double-humped profile for vertical ground reaction force (GRF) with reduced ankle push off power and walking speed for OI subjects. Moreover, a comparison of vertical GRFs in OI subjects with that of healthy subjects suggests lower values for the former. The results encourage and motivate for further investigation with a bigger set of subjects.

CONCLUSION

This information may be useful in developing a better understanding of pathological gait in type IV OI subjects, which ultimately helps the design of subject-specific implants, surgical preplanning, and rehabilitation.

Oro-dental and cranio-facial characteristics of osteogenesis imperfecta type V

Osteogenesis imperfecta (OI) type V is an ultrarare heritable bone disorder caused by the heterozygous c.-14C > T mutation in IFITM5. The oro-dental and craniofacial phenotype has not been described in detail, which we therefore undertook to evaluate in a multicenter study (Brittle Bone Disease Consortium). Fourteen individuals with OI type V (age 3-50 years; 10 females, 4 males) underwent dental and craniofacial assessment. None of the individuals had dentinogenesis imperfecta. Six of the 9 study participants (66%) for whom panoramic radiographs were obtained had at least one missing tooth (range 1-9). Class II molar occlusion was present in 8 (57%) of the 14 study participants. The facial profile was retrusive and lower face height was decreased in 8 (57%) individuals. Cephalometry, performed in three study participants, revealed a severely retrusive maxilla and mandible, and moderately to severly retroclined incisors in a 14-year old girl, a protrusive maxilla and a retrusive mandible in a 14-year old boy. Cone beam computed tomograpy scans were obtained from two study participants and demonstrated intervertebral disc calcification at the C2-C3 level in one individual. Our study observed that OI type V is associated with missing permanent teeth, especially permanent premolar, but not with dentinogenesis imperfecta. The pattern of craniofacial abnormalities in OI type V thus differs from that in other severe OI types, such as OI type III and IV, and could be described as a bimaxillary retrusive malocclusion with reduced lower face height and multiple missing teeth.

Oral health-related quality of life in children and adolescents with osteogenesis imperfecta: cross-sectional study

Background

Osteogenesis imperfecta (OI) affects dental and craniofacial development and may therefore impair Oral Health-Related Quality of Life (OHRQoL). However, little is known about OHRQoL in children and adolescents with OI. The aim of this study was to explore the influence of OI severity on oral health-related quality of life in children and adolescents.

Methods

Children and adolescents aged 8–14 years were recruited in the context of a multicenter longitudinal study (Brittle Bone Disease Consortium) that enrolls individuals with OI in 10 centers across North America. OHRQoL was assessed using the Child Perceptions Questionnaire (CPQ) versions for 8 to 10-year-olds (CPQ_8–10) and for 11 to 14-year-olds (CPQ_11–14).

Results

A total of 138 children and adolescents (62% girls) diagnosed with OI types I, III, IV, V and VI (n = 65, 30, 37, 4 and 2, respectively) participated in the study. CPQ_8–10 scores were similar between OI types in children aged 8 to 10 years. In the 11 to 14-year-old group, CPQ_11–14-scores were significantly higher (i.e. worse) for OI types III (24.7 [SD 12.5]) and IV (23.1 [SD 14.8]) than for OI type I (16.5 [SD 12.8]) (P < 0.05). The difference between OI types was due to the association between OI types and the functional limitations domain, as OI types III and IV were associated with significantly higher grade of functional limitations compared to OI type I.

Conclusion

The severity of OI impacts OHRQoL in adolescents aged 11 to 14 years, but not in children age 8 to 10 years.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0935-y) contains supplementary material, which is available to authorized users.

Dental and craniofacial characteristics caused by the p.Ser40Leu mutation in IFITM5

Severe forms of osteogenesis imperfecta (OI) are usually caused by mutations in genes that code for collagen Type I and frequently are associated with craniofacial abnormalities. However, the dental and craniofacial characteristics of OI caused by the p.Ser40Leu mutation in the IFITM5 gene have not been reported. We investigated a 15-year-old girl with severe OI caused by this mutation. She had marked deformations of extremity long bones. There were no clinical or radiological signs of dentinogenesis imperfecta, but one tooth was missing and several teeth were impacted. Cone beam computed tomography revealed a generalized osteopenic appearance of the craniofacial skeleton, bilateral enlargement of mandibular bodies, and areas of cortical erosions. The cranial base and skull showed a generalized granular bone pattern with a mixture of osteosclerosis and osteolysis. Sphenoid and frontal sinuses were congenitally missing. Cephalometric analysis indicated a Class III growth pattern. In this case, the IFITM5 p.Ser40Leu mutation did not affect tooth structure but was associated with deformities in craniofacial bones that resemble those in the other parts of the skeleton.

Heterozygous WNT1 variant causing a variable bone phenotype

Osteogenesis imperfecta (OI) is a family of heritable disorders of bone fragility. Most individuals with OI have mutations in the genes encoding type I collagen; at least 17 other genes have been associated with OI. Biallelic loss-of-function mutations in WNT1 cause severe OI. Heterozygous missense variants in WNT1 are responsible for early-onset osteoporosis with variable bone phenotypes. Herein, we report a third-generation family with four affected individuals, some presenting with multiple low-impact fractures in childhood and others presenting with early-onset osteoporosis without a striking fracture history. A WNT1 variant (c. 1051 > C; p.Trp351Arg) was identified in the proband and segregated with a bone phenotype in three additional family members, consistent with autosomal dominant inheritance. In the proband, whole genome sequencing also revealed a de novo duplication (434 kb) of 22q11.2 that involves 25 genes, 4 of which are associated with human disease when haploinsufficient. Though smaller than the typical (1.5 Mb) 22q11.2 duplication, the duplication in the proband may be responsible for additional nonosseous aspects of his phenotype (hypotonia, developmental delay, small genitalia, strabismus, and depression in preadolescence). This case demonstrates the variability of bone phenotype conferred by a WNT1 variant and extends the spectrum of bone phenotypes associated with heterozygous WNT1 mutations.

Novel WNT1 mutations in children with osteogenesis imperfecta: Clinical and functional characterization

INTRODUCTION

Biallelic mutations in WNT1 can give rise to a rare form of moderate to severe OI. Here we report on 12 children (age 2 to 16 years; 5 girls) with biallelic WNT1 mutations.

METHODS

Genomic DNA was analyzed either by targeted next-generation sequencing or Sanger sequencing. Mutations were modeled on the WNT1 protein structure. The in vitro functional effect of WNT1 mutations on WNT signaling was assessed in HEK293 cells using the topflash reporter assay system.

RESULTS

All patients had lower extremity deformities and vertebral compression fractures. Seven individuals had upper extremity deformities. Intellectual development appeared normal in 11 children, but was clearly impaired in a 3-year old boy. Ptosis was noted in 7 patients. Height z-scores varied widely, from -7.2 to +1.5. A total of 11 disease-causing WNT1 variants (7 missense mutations, 4 mutations leading to premature termination codons) were identified, of which 9 were novel. Three-dimensional protein modeling suggested that each of the missense mutations led to structural modifications. Functional in vitro studies revealed that all observed missense mutations led to decreased ability of WNT1 to induce WNT signaling via the canonical WNT pathway.

CONCLUSIONS

The reported biallelic WNT1 variants cause loss of WNT1 function and lead to a severe bone fragility phenotype with conspicuous involvement of the spine.

Cumulative radiation exposure from medical imaging and associated lifetime cancer risk in children with osteogenesis imperfecta

OBJECTIVES

To estimate the cumulative effective dose of radiation (E) and additional lifetime attributable risk (LAR) of cancer from ionizing radiation in children with osteogenesis imperfecta (OI), who require frequent imaging for fractures and bone densitometry (DXA) surveillance. Also, to evaluate the pattern of long bone fractures.

METHODS

We reviewed all imaging (x-rays, DXA and computed tomography [CT]) conducted in a cohort of children with OI with a minimum observation period of 5 years. For each image, E was estimated using age-dependent local data, and LAR of cancer was extrapolated. LAR and fracture data were compared among children with mild, moderate and severe OI. LAR was allocated to cancer risk categories, and the moderate risk group (1 in 1000 to 1 in 100) was evaluated further.

RESULTS

Results from 106 children with OI (50% females, 5747 images) are presented, with a median (range) observation period of 11.7 (5.2-15.6) years. CT accounted for 0.8% of total imaging procedures but contributed to 66% of total E. The overall LAR of cancer was minimal, averaging an additional 8.8 cases per 100,000 exposed patients (0.8-403). LAR was significantly lower in children with mild OI compared to those with moderate (p = 0.006) and severe OI (p = 0.001). All patients with a moderate LAR of cancer (n = 8) had undergone CT scans and 88% had scoliosis or vertebral fractures. The cohort experienced 412 long bone fractures, with the most common site being the femur (26.5%). OI severity correlated positively with long bone fracture rates (p < 0.001).

CONCLUSIONS

When compared to baseline LAR of cancer (50%) the additional cancer risk from ionizing radiation imaging in our paediatric OI cohort was small (0.0088%). To reduce additional cancer risk, we recommend replacing spinal x-rays with vertebral fracture assessments on DXA and exercising caution with CT imaging.

Elevated platelet counts in a cohort of children with moderate-severe osteogenesis imperfecta suggest that inflammation is present

BACKGROUND

Elevated platelet counts are observed in cancer, autoimmunity and inflammation with concurrent illness. Proinflammatory cytokines are elevated in murine osteogenesis imperfecta (OI) models. We hypothesised that platelet counts might be elevated in children with moderate-severe OI.

METHODS

We reviewed the hospital records of 71 children with moderate-severe OI, treated in the Sheffield Children's Hospital's Severe, Complex and Atypical Osteogenesis Imperfecta Highly Specialised Service. Data relating platelet count (below/above average, above upper limit) to prior and concurrent events were summarised as event proportions per child. Additionally, we created platelet SD scores to assess age and time-related trends, and relationship with OI type.

RESULTS

1206 platelet counts were recorded. Platelet SD scores were right-shifted by 0.89 SD overall. 49 of 71 (69%) patients had at least one platelet count above the normal range and 246 (20.4%) of all counts were above the upper limit of normal. Of these, 101 (41%) were high despite no confounding factors being present. For the 47 children with data at age less than 2 years, 89 (30.0%) platelet counts were above the upper limit of normal and 39 (44%) had no associated confounding factor. Elevated platelet counts were recorded most often for children with new or existing vertebral fractures.

CONCLUSIONS

Raised platelet counts were observed in association with new and healing vertebral fractures, but also (41%-44%) in the absence of identified proinflammatory factors or events. We speculate that these findings are evidence for a proinflammatory component to OI that could be a target for therapeutic intervention.

Mutations That Alter the Carboxy-Terminal-Propeptide Cleavage Site of the Chains of Type I Procollagen Are Associated With a Unique Osteogenesis Imperfecta Phenotype

Osteogenesis imperfecta (OI) is a genetic bone disorder characterized by fractures, low bone mass, and skeletal fragility. It most commonly arises from dominantly inherited mutations in the genes COL1A1 and COL1A2 that encode the chains of type I collagen. A number of recent reports have suggested that mutations affecting the carboxyl-terminal propeptide cleavage site in the products of either COL1A1 or COL1A2 give rise to a form of OI characterized by unusually dense bones. We have assembled clinical, biochemical, and molecular data from 29 individuals from 8 families with 7 different mutations affecting the C-propeptide cleavage site. The phenotype was generally mild: The median height was ∼33th centile. Eighty percent of subjects had their first fracture by the age of 10 years, and one-third had a femoral or tibial fracture by the age of 25 years. Fractures continued into adulthood, though rates varied considerably. Healing was normal and rarely resulted in long bone deformity. One-third of subjects older than 15 years had scoliosis. The teeth and hearing were normal in most, and blue sclerae were not observed. Other features noted included fibro-osseous dysplasia of the mandible and Achilles tendon calcification. The mean spinal bone mineral density Z-score was +2.9 (SD 2.1) compared with -2.2 (0.7) in subjects with COL1A1 haploinsufficiency mutations. Bone mineral density distribution, assessed by quantitative backscattered electron imaging in bone showed higher levels of mineralization than found in any other disorder. Bone histology showed high trabecular volume and increased cortical thickness, with hyperosteoidosis and delayed mineralization. In vitro studies with cultured skin fibroblasts suggested that these mutations interfere with processing of the chain in which the sequence alteration occurs, but the C-propeptide is eventually cleaved (and detectable in blood), suggesting there are alternative sites of cleavage. The precise mechanism of the bony pathology is not yet clear. © 2018 American Society for Bone and Mineral Research.

Pulmonary and diaphragmatic pathology in collagen type I α1 mutant mice with osteogenesis imperfecta

BackgroundOsteogenesis imperfecta (OI) is most often caused by mutations in type I collagen genes. Respiratory complications have been largely attributed to spine and ribcage deformities. We hypothesized that direct involvement of the pulmonary parenchyma and/or diaphragm by the disease may occur.MethodsIn Col1a1^Jrt/+ mice, a model of severe dominant OI, mean linear intercept length (Lm) was used to assess the distal airspace size. Cross-sectional area (CSA) and myosin heavy chain (MyHC) phenotype of the diaphragm muscle fibers, as well as contractile properties, were determined. OI mice were also treated with neutralizing antibodies against transforming growth factor-β (TGF-β).ResultsDistal airspace enlargement occurred in OI mice (Lm +27%). Diaphragmatic thickness and fiber number were reduced, with increases in fast-twitch type IIx/IIb MyHC fibers. Ex vivo force generation (normalized for CSA) of the diaphragm was also significantly reduced. The increased Lm values found in OI mice were not prevented by anti-TGF-β antibody treatment.ConclusionsThe Col1a1^Jrt/+ mouse model of OI demonstrates: (1) pulmonary airspace enlargement not driven by TGF-β; and (2) reduced muscle mass and intrinsic contractile weakness of the diaphragm. These results suggest a complex and multifaceted basis for respiratory complications in OI that cannot be solely attributed to bone manifestations.

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.

Anabolic Therapy for the Treatment of Osteoporosis in Childhood

PURPOSE OF REVIEW

Numerous forms of osteoporosis in childhood are characterized by low bone turnover (for example, osteoporosis due to neuromuscular disorders and glucocorticoid exposure). Anti-resorptive therapy, traditionally used to treat osteoporosis in the young, is associated with further reductions in bone turnover, raising concerns about the long-term safety and efficacy of such therapy. These observations have led to increasing interest in the role of anabolic therapy to treat pediatric osteoporosis.

RECENT FINDINGS

While growth hormone and androgens appears to be relatively weak anabolic modulators of bone mass, emerging therapies targeting bone formation pathways (anti-transforming growth factor beta antibody and anti-sclerostin antibody) hold considerable promise. Teriparatide remains an attractive option that merits formal study for patients post-epiphyseal fusion, although it must be considered that adult studies have shown its effect is blunted when administered following bisphosphonate therapy. Mechanical stimulation of bone through whole body vibration therapy appears to be much less effective than bisphosphonate therapy for treating osteoporosis in children. New anabolic therapies which target important pathways in skeletal metabolism merit further study in children, including their effects on fracture risk reduction and after treatment discontinuation.

Consensus guidelines on the use of bisphosphonate therapy in children and adolescents

Bisphosphonate therapy is the mainstay of pharmacological intervention in young people with skeletal fragility. The evidence of its use in a variety of conditions remains limited despite over three decades of clinical experience. On behalf of the Australasian Paediatric Endocrine Group, this evidence-based consensus guideline presents recommendations and discusses the graded evidence (using the GRADE system) for these recommendations. Primary bone fragility disorders such as osteogenesis imperfecta are considered separately from osteoporosis secondary to other clinical conditions (such as cerebral palsy, Duchenne muscular dystrophy). The use of bisphosphonates in non-fragility conditions, such as fibrous dysplasia, avascular necrosis, bone cysts and hypercalcaemia, is also discussed. While these guidelines provide an evidence-based approach where possible, further research is required in all clinical applications in order to strengthen the recommendations made.