Developments in rare bone diseases and mineral disorders

Efficacy of Bisphosphonate for Urolithiasis Complicated by Osteogenesis Imperfecta

A 44-year-old man with osteogenesis imperfecta presented with left renal colic. Non-contrast computed tomography revealed a stone (10×9 mm) in the left upper ureter. Ureteroscopic lithotripsy was performed twice and stone-free status was achieved. An analysis of the stone revealed a mixed composition including calcium oxalate and calcium phosphate. Postoperatively, we administered bisphosphonates to prevent recurrence of urolithiasis, as 24-hour urine collection revealed marked hypercalciuria. Eighteen months after surgery, the urinary calcium levels had normalized, and there was no recurrence of urolithiasis. Osteogenesis imperfecta can be complicated by urolithiasis, but bisphosphonates may be useful in preventing recurrence of this disease.

The intricate mechanism of PLS3 in bone homeostasis and disease

Since our discovery in 2013 that genetic defects in PLS3 lead to bone fragility, the mechanistic details of this process have remained obscure. It has been established that PLS3 variants cause syndromic and nonsyndromic osteoporosis as well as osteoarthritis. PLS3 codes for an actin-bundling protein with a broad pattern of expression. As such, it is puzzling how PLS3 specifically leads to bone-related disease presentation. Our review aims to summarize the current state of knowledge regarding the function of PLS3 in the predominant cell types in the bone tissue, the osteocytes, osteoblasts and osteoclasts. This is related to the role of PLS3 in regulating mechanotransduction, calcium regulation, vesicle trafficking, cell differentiation and mineralization as part of the complex bone pathology presented by PLS3 defects. Considering the consequences of PLS3 defects on multiple aspects of bone tissue metabolism, our review motivates the study of its mechanism in bone diseases which can potentially help in the design of suitable therapy.

Systematic review of health related-quality of life in adults with osteogenesis imperfecta

BACKGROUND

Osteogenesis imperfecta (OI) is a rare, connective tissue disorder characterised by bone fragility, resulting in recurrent fractures and skeletal deformities. Extra-skeletal manifestations include dentinogenesis imperfecta, hearing abnormalities and lung disease. These co-morbidities combined with recurrent fractures can exert a significant impact on health-related quality of life (HR-QOL). It is important to assess HR-QOL throughout adulthood because the prevalence of some OI-specific complications increases with age.

METHODS

PubMed, EMBASE and CENTRAL databases were searched on 2nd February 2022 to identify studies reporting quantitative assessments of HR-QOL in adults with OI. The primary endpoint was to determine the impact of an OI diagnosis on adult's HR-QOL. Secondary endpoints were to (i) examine how frequently various HR-QOL assessment tools were used (ii) identify differences in HR-QOL between OI types and (iii) investigate the determinants of HR-QOL in adults with OI. Search results were exported to Endnote where two reviewers independently conducted title/abstract and full-text reviews. Data from accepted studies were extracted into Microsoft Excel. A narrative synthesis was then undertaken.

RESULTS

The review identified 17 studies with a total of 1,648 adults. The Short Form-36 (SF-36) was the most frequently reported HR-QOL assessment tool and was used in nine studies. Physical HR-QOL was reduced in adults with OI. Physical component scores (PCS) or individual physical domains of the SF-36 were lower in eight of nine studies. Mental component scores (MCS) were preserved in all six studies, however individual mental health domains of the SF-36 were reduced in some studies. The prevalence of anxiety/depression was relatively low in adults with OI. Those with type III OI had lower physical and respiratory HR-QOL but preserved mental HR-QOL compared with type I. The prevalence of fatigue and pain was higher in adults with OI compared with reference populations. Age and cardio-pulmonary co-morbidities were associated with lower HR-QOL.

CONCLUSION

OI in adulthood has a wide-ranging negative impact on HR-QOL. Physical and respiratory HR-QOL were lower, while the prevalence of pain and fatigue were higher than in reference populations. Mental HR-QOL was relatively preserved, although some deficits were identified. Age and cardio-pulmonary co-morbidities were associated with lower HR-QOL.

Prevalence of depression and anxiety, and their relationship to social support among patients and family caregivers of rare bone diseases

BACKGROUND

Rare bone diseases (RBDs) are a set of inherited rare diseases that can cause disability and have a devastating impact on families affected, which may lead to a particular high prevalence of psychological disorders in patients and caregivers. Social support plays a role in the well-being of families with rare disease patients, but its effect on psychology of RBD families remains unclear. The purpose of the current cross-sectional quantitative study was to investigate the frequency of depression and anxiety, and their relationship with social support among RBD patients and family caregivers.

RESULTS

A total of 196 participants responded to the questionnaire, including 72 patients and 124 caregivers. Depression was detected among 33.8% of patients and 57% of caregivers, and anxiety disorder was presented in 28.6% of patients and 50% of caregivers. Higher depression scores and anxiety scores were found in both patients and caregivers with an education level of ≤ middle school and monthly income of ≤ ￥2000 (all P < 0.05). The mean (SD) scores of Social Support Rating Scales in patients and caregivers were 37.06 (8.05) and 38.31 (5.76), respectively. After adjusting for gender, age, monthly income, education, employment and marital status, the reverse associations between depression scores, anxiety scores and social support were found merely in caregivers (depression & social support: β = - 0. 46, P < 0.001, anxiety & social support: β = - 0. 44, P < 0.001), specifically for subjective support (depression & subjective support: β = - 0.94, P < 0.001, anxiety & subjective support: β = - 0.87, P < 0.001).

CONCLUSIONS

The study identified a high prevalence of depression and anxiety among RBD patients and caregivers, and pointed out the significance of social support in alleviating psychological distress. In order to provide RBD families with comprehensive assistance, the government should actively develop programs aimed at psychological aid, policy advocacy and tangible support.

Treatment for subtrochanteric fracture and subsequent nonunion in an adult patient with osteopetrosis: A case report and review of the literature

BACKGROUND

As a congenital metabolic bone disease caused by defective osteoclastic resorption of immature bone, osteopetrosis is characterized by diffused sclerosis of bones, brittle bones, easy fracturing, narrow medullary canals, and a weak fracture healing ability. At present, clear standards and principles for the treatment of fractures in patients with osteopetrosis are lacking. Non-operative treatment can prevent fracture hematoma and preserve the blood supply to the bone fragments, while being associated with frequent failures and higher mortality rates. Meanwhile, closed reduction and internal fixation with intramedullary nail (CRIF + IMN) approaches can also protect blood supply to the fracture site. However, IMN cannot be used for the vast majority of patients with osteopetrosis due to the narrowing of medullary canals. Thus, open reduction and internal fixation with plate remains the most appropriate surgical method for treating fractures in patients with osteopetrosis, but this approach is complicated by the lack of intramedullary hematopoiesis in such patients. Fracture healing primarily depends on the blood supply to the external periosteum. Open reduction can also easily destroy the periosteum and cause delayed fracture healing or even nonunion; however, CRIF may be the most practical approach. As a result, it would be prudent to solve the difficulty of drilling during the operation and the problem of postoperative nonunion.

CASE SUMMARY

In 2018, we treated an adult patient with osteopetrosis presenting with a subtrochanteric fracture. The fracture was fixed using a femoral locking compression plate. Because of delayed consolidation, at 12 mo postoperatively the patient was further treated with platelet-rich plasma (PRP) combined with radial extracorporeal shock wave therapy (rESWT). Antero-posterior and lateral radiographs obtained at the latest follow-up (10 mo) showed that the callus had grown at the original fracture site, and the medial fracture line almost disappeared.

CONCLUSION

Osteosynthesis remains the first choice of treatment approach for fractures in patients with osteopetrosis, especially peritrochanteric fractures. Preoperative preparation is necessary to avoid risks such as drill bit breakage and iatrogenic fracture during the operation. Moreover, fractures in a patient with osteopetrosis present with a high risk of delayed union and nonunion, which can be potentially cured with PRP + rESWT.

Comprehensive pain management strategy for infants with moderate to severe osteogenesis imperfecta in the perinatal period

Osteogenesis imperfecta (OI) is a rare genetic heterogeneous disorder that causes increased bone fragility and recurrent fractures. For infants with OI and diffuse fractures, pain management, which is nuanced and specific for this population, is of the utmost importance to their neonatal care. Through experience at our center, we have developed a standard approach that has been successful in optimizing survival for these infants during this tenuous period. In this paper, we outline our multidisciplinary approach to pain management for infants with moderate to severe OI during the neonatal period, with emphasis on promotion of fracture healing and adequate pain control.

Collagen transport and related pathways in Osteogenesis Imperfecta

Osteogenesis Imperfecta (OI) comprises a heterogeneous group of patients who share bone fragility and deformities as the main characteristics, albeit with different degrees of severity. Phenotypic variation also exists in other connective tissue aspects of the disease, complicating disease classification and disease course prediction. Although collagen type I defects are long established as the primary cause of the bone pathology, we are still far from comprehending the complete mechanism. In the last years, the advent of next generation sequencing has triggered the discovery of many new genetic causes for OI, helping to draw its molecular landscape. It has become clear that, in addition to collagen type I genes, OI can be caused by multiple proteins connected to different parts of collagen biosynthesis. The production of collagen entails a complex process, starting from the production of the collagen Iα1 and collagen Iα2 chains in the endoplasmic reticulum, during and after which procollagen is subjected to a plethora of posttranslational modifications by chaperones. After reaching the Golgi organelle, procollagen is destined to the extracellular matrix where it forms collagen fibrils. Recently discovered mutations in components of the retrograde transport of chaperones highlight its emerging role as critical contributor of OI development. This review offers an overview of collagen regulation in the context of recent gene discoveries, emphasizing the significance of transport disruptions in the OI mechanism. We aim to motivate exploration of skeletal fragility in OI from the perspective of these pathways to identify regulatory points which can hint to therapeutic targets.

A novel mutation in TNFRSF11A gene causes pediatric osteopetrosis: case report

BACKGROUND

Osteopetrosis is a rare inherited bone disorder affected individual by osteoclast disfunction and increasing bone density. Surgery was taken for histological examination of the specimen and evidence of malignancy was not found. Finally, X-ray and gene detection lead to the diagnosis.

CASE PRESENTATION

We report a 10-year-old girl with two years history of pus rhinorrhea, nasal obstruction and smelly nose. She was diagnosed and treated as sinusitis. But the symptoms were recurrent. Ten months ago, she was afflicted with persistent swelling and broken skin on the right cheek. All the laboratory findings showed normal. During surgery, we resected the right gingiva, the right nasal mucosa and the right facial tissue for biopsies. Histological examination showed proliferation of granulation tissue in chronic inflammatory mucosa. X-rays showed generalized sclerosis. Genetic analysis strongly supported a novel mutation of TNFRSF11A gene which caused osteoporosis. We found a novel mutation of the c.1196C > G (p.S399X) in exon 9 of TNFRSF11A. The TNFRSF11A gene encodes RANK, which is fundamental for osteoclast formation.

CONCLUSION

Osteopetrosis is a rare genetic bone disease characterized by increased bone density because of bone resorption failure. Diagnosis is based on X-ray and gene analyze. Osteoclasts are bone-related cells derived from hematopoietic cell lines. Since osteoclasts arise from a hematopoietic progenitor cell of the monocytic lineage, the defect can be corrected by hematopoietic stem cell transplantation (HSCT). Better understanding of this pathological situation and pathogenesis is so important to plan appropriate immunotherapy to benefit.

Metabolic Bone Diseases in the Pediatric Population

Bone plays an important role in regulating mineral balance in response to physiologic needs. In addition, bone is subject to a continuous remodeling process to maintain healthy bone mass and growth. Metabolic bone diseases are a heterogeneous group of diseases caused by abnormalities of bone mass, mineral structure homeostasis, bone turnover, or bone growth. In pediatrics, several significant advances have been made in recent years in the diagnosis of metabolic bone diseases (e.g., osteogenesis imperfecta, hyperparathyroidism, rickets, renal osteodystrophy, pediatric osteoporosis, and osteopetrosis). Imaging is fundamental in the diagnosis of these pathologies.

Rare Diseases of the Middle Ear and Lateral Skull Base

Otalgia, otorrhea and hearing loss are the most common ear-related symptoms that lead to the consultation of an otolaryngologist. Furthermore, balance disorders and affections of the cranial nerve function may play a role in the consultation. In large academic centres, but also in primary care, the identification of rare diseases of the middle ear and the lateral skull base is essential, as these diseases often require interdisciplinary approaches to establish the correct diagnosis and to initiate safe and adequate treatments. This review provides an overview of rare bone, neoplastic, haematological, autoimmunological and infectious disorders as well as malformations that may manifest in the middle ear and the lateral skull base. Knowledge of rare disorders is an essential factor ensuring the quality of patient care, in particular surgical procedures. Notably, in untypical, complicated, and prolonged disease courses, rare differential diagnoses need to be considered.

Adiponectin signalling in bone homeostasis, with age and in disease

Adiponectin is the most abundant circulating adipokine and is primarily involved in glucose metabolism and insulin resistance. Within the bone, osteoblasts and osteoclasts express the adiponectin receptors, however, there are conflicting reports on the effects of adiponectin on bone formation and turnover. Many studies have shown a pro-osteogenic role for adiponectin in in vivo murine models and in vitro: with increased osteoblast differentiation and activity, alongside lower levels of osteoclastogenesis. However, human studies often demonstrate an inverse relationship between adiponectin concentration and bone activity. Moreover, the presence of multiple isoforms of adiponectin and multiple receptor subtypes has the potential to lead to more complex signalling and functional consequences. As such, we still do not fully understand the importance of the adiponectin signalling pathway in regulating bone homeostasis and repair in health, with age and in disease. In this review, we explore our current understanding of adiponectin bioactivity in the bone; the significance of its different isoforms; and how adiponectin biology is altered in disease. Ultimately, furthering our understanding of adiponectin regulation of bone biology is key to developing pharmacological and non-pharmacological (lifestyle) interventions that target adiponectin signalling to boost bone growth and repair in healthy ageing, following injury or in disease.

Subtrochanteric Femoral Fracture in a Patient with Osteopetrosis: Treated with Internal Fixation and Complicated by Intraoperative Femoral Neck Fracture

Objective

Osteopetrosis (OP) is a rare, heritable skeletal disorder that is caused by osteoclast dysfunction, leading to failure of bone resorption and increased bone density. The fragility of such dense bone may result in an increased incidence of fractures. Furthermore, surgery in patients with OP is associated with increased technical difficulty and a higher risk of complications.

Case Report

We report a case of a 20-year-old woman with autosomal dominant OP who developed a subtrochanteric femoral fracture. The fracture was treated by open reduction and internal fixation using a dynamic hip screw. Although technical difficulties were experienced and an intraoperative femoral neck fracture occurred, the surgical outcome was satisfactory. Union of the fractures was visible on radiographs obtained 12 months postoperatively. At 2 years postoperatively, the patient was completely free of any complications resulting from her injury and treatment.

Conclusion

Open reduction and internal fixation may be an effective option for fractures in patients with OP. Orthopedic surgeons should be aware that the increased density and stiffness of osteopetrotic bone increases the risks of intraoperative technical difficulties, iatrogenic fractures, and postoperative complications.

Hearing loss in individuals with osteogenesis imperfecta in North America: Results from a multicenter study

Hearing loss (HL) is an extra-skeletal manifestation of the connective tissue disorder osteogenesis imperfecta (OI). Systematic evaluation of the prevalence and characteristics of HL in COL1A1/COL1A2-related OI will contribute to a better clinical management of individuals with OI. We collected and analyzed pure-tone audiometry data from 312 individuals with OI who were enrolled in the Linked Clinical Research Centers and the Brittle Bone Disorders Consortium. The prevalence, type, and severity of HL in COL1A1/COL1A2-related OI are reported. We show that the prevalence of HL in OI is 28% and increased with age in Type I OI but not in Types III and IV. Individuals with OI Types III and IV are at a higher risk to develop HL in the first decade of life when compared to OI Type I. We also show that the prevalence of SNHL is higher in females with OI compared to males. This study reveals new insights regarding prevalence of HL in OI including a lower general prevalence of HL in COL1A1/COL1A2-related OI than previously reported (28.3 vs. 65%) and high prevalence of SNHL in females. Our data support the need in early routine hearing evaluation in all types of OI that can be adjusted to the severity of the skeletal disease.

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.

Mobility in osteogenesis imperfecta: a multicenter North American study

PURPOSE

Osteogenesis imperfecta (OI) is a genetic connective tissue disorder that causes bone fragility. Phenotypic severity influences ability to walk, however, little is known about ambulatory characteristics of individuals with OI, especially in more severe forms. The purpose of this work was to characterize mobility in OI using standard clinical assessment tools and determine if patient characteristics could be used to predict mobility outcomes.

METHODS

We collected mobility data at five clinical sites to analyze the largest cohort of individuals with OI (n = 491) to date. Linear mixed models were developed to explore relationships among subject demographics and mobility metrics.

RESULTS

Results showed minor limitations in the mild group while the more severe types showed more significant limitations in all mobility metrics analyzed. Height and weight were shown to be the most significant predictors of mobility. Relationships with mobility and bisphosphonates varied with OI type and type used (oral/IV).

CONCLUSION

These results are significant to understanding mobility limitations of specific types of OI and beneficial when developing rehabilitation protocols for this population. It is important for physicians, patients, and caregivers to gain insight into severity and classification of the disease and the influence of disease-related characteristics on prognosis for mobility.

Genetic Disorders of the Extracellular Matrix

Mutations in the genes for extracellular matrix (ECM) components cause a wide range of genetic connective tissues disorders throughout the body. The elucidation of mutations and their correlation with pathology has been instrumental in understanding the roles of many ECM components. The pathological consequences of ECM protein mutations depend on its tissue distribution, tissue function, and on the nature of the mutation. The prevalent paradigm for the molecular pathology has been that there are two global mechanisms. First, mutations that reduce the production of ECM proteins impair matrix integrity largely due to quantitative ECM defects. Second, mutations altering protein structure may reduce protein secretion but also introduce dominant negative effects in ECM formation, structure and/or stability. Recent studies show that endoplasmic reticulum (ER) stress, caused by mutant misfolded ECM proteins, makes a significant contribution to the pathophysiology. This suggests that targeting ER‐stress may offer a new therapeutic strategy in a range of ECM disorders caused by protein misfolding mutations. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Osteopetrosis-Anesthetic Considerations for Total Knee Arthroplasty: A Case Report

Autosomal dominant or benign osteopetrosis is a rare genetic disorder of osteoclasts that results in dense but brittle bone structures. Patients with osteopetrosis may be scheduled for total knee arthroplasty to treat painful and functionally limiting osteoarthrosis. A search of the published literature produced no citation concerning anesthesia for patients with autosomal dominant osteopetrosis undergoing total knee arthroplasty. We present a case report detailing our experience and discuss considerations for the care of future patients with autosomal dominant osteopetrosis.

Craniofacial skeleton of MEXICAN tetra (Astyanax mexicanus): As a bone disease model

A small fresh water fish, the Mexican tetra (Astyanax mexicanus) is a novel animal model in evolutionary developmental biology. The existence of morphologically distinct surface and cave morphs of this species allows simultaneous comparative analysis of phenotypic changes at different life stages. The cavefish harbors many favorable constructive traits (i.e., large jaws with an increased number of teeth, neuromast cells, enlarged olfactory pits and excess storage of adipose tissues) and regressive traits (i.e., reduced eye structures and pigmentation) which are essential for cave adaptation. A wide spectrum of natural craniofacial morphologies can be observed among the different cave populations. Recently, the Mexican tetra has been identified as a human disease model. The fully sequenced genome along with modern genome editing tools has allowed researchers to generate transgenic and targeted gene knockouts with phenotypes that resemble human pathological conditions. This review will discuss the anatomy of the craniofacial skeleton of A. mexicanus with a focus on morphologically variable facial bones, jaws that house continuously replacing teeth and pharyngeal skeleton. Furthermore, the possible applications of this model animal in identifying human congenital and metabolic skeletal disorders is addressed. Developmental Dynamics 248:153-161, 2019. © 2018 Wiley Periodicals, Inc.

Burosumab in X-linked hypophosphatemia: a profile of its use in the USA

Burosumab (Crysvita^®), a fully human IgG1 monoclonal antibody directed at fibroblast growth factor 23 (FGF23), is indicated for the treatment of X-linked hypophosphatemia (XLH), a condition associated with excessive FGF23 production. It directly addresses the excessive FGF23 activity in patients with XLH by binding to FGF23, and inhibiting its signaling. This leads to increased gastrointestinal phosphate absorption and renal phosphate reabsorption, thereby improving serum phosphate levels, and, ultimately, bone mineralization and the risk of bone disease. In clinical trials, subcutaneous burosumab increased serum phosphorus levels in pediatric and adult patients with XLH, as well as significantly improving the severity of rickets in children, and improving pain, stiffness, physical functioning, and fracture/pseudofracture healing in adults. Burosumab is well tolerated by children and adults with XLH, with most treatment-emergent adverse events being of mild to moderate severity.