The Erlenmeyer flask bone deformity in the skeletal dysplasias

Preclinical Rodent Models for Human Bone Disease, Including a Focus on Cortical Bone

Preclinical models (typically ovariectomized rats and genetically altered mice) have underpinned much of what we know about skeletal biology. They have been pivotal for developing therapies for osteoporosis and monogenic skeletal conditions, including osteogenesis imperfecta, achondroplasia, hypophosphatasia, and craniodysplasias. Further therapeutic advances, particularly to improve cortical strength, require improved understanding and more rigorous use and reporting. We describe here how trabecular and cortical bone structure develop, are maintained, and degenerate with aging in mice, rats, and humans, and how cortical bone structure is changed in some preclinical models of endocrine conditions (eg, postmenopausal osteoporosis, chronic kidney disease, hyperparathyroidism, diabetes). We provide examples of preclinical models used to identify and test current therapies for osteoporosis, and discuss common concerns raised when comparing rodent preclinical models to the human skeleton. We focus especially on cortical bone, because it differs between small and larger mammals in its organizational structure. We discuss mechanisms common to mouse and human controlling cortical bone strength and structure, including recent examples revealing genetic contributors to cortical porosity and osteocyte network configurations during growth, maturity, and aging. We conclude with guidelines for clear reporting on mouse models with a goal for better consistency in the use and interpretation of these models.

A new case of Melnick-Needles syndrome with skeletal manifestations: A case report

INTRODUCTION AND IMPORTANCE

Melnick-Needles syndrome (MNS) is a rare skeletal dysplasia that affects skeletal and connective tissue. Less than 70 cases of MNS reported in the literature. MNS had various clinical manifestations such as skeletal deformity, cortical bony sclerosis, facial abnormality, and urogenital symptoms.

CASE PRESENTATION

We presented a 5-year-old girl who referred to our orthopedic clinic with knee valgus deformity, spinal kyphoscoliosis, bilateral coxa valga, and humerus cortical irregularity. Based on some facial and skeletal feature, MNS was confirmed with genetic evaluation (heterozygote Filamin A genome).

CLINICAL DISCUSSION

The diagnosis of MNS requires a thorough medical and family history, physical examination, and radiographic evaluation. Differential diagnoses for patients with skeletal and facial deformities like MNS include Camurati-Engelmann disease, cystinuria, Galloway-Mowat syndrome, Joubert syndrome, and mucopolysaccharidosis. Treatment for MNS patients with bony deformities without lethal conditions can be conservative, but corrective surgery may be necessary in some cases.

CONCLUSIONS

MNS was a rare syndrome with common clinical manifestations such as limb and spine deformity. It is important to conduct a careful examination of any patient who presents with limb and skeletal deformity to the orthopedic clinic, as the disease may have some lethal clinical implications.

Autosomal dominant osteopetrosis

Autosomal dominant osteopetrosis (ADO) is the most common form of osteopetrosis. ADO is characterized by generalized osteosclerosis along with characteristic radiographic features such as a "bone-in-bone" appearance of long bones and sclerosis of the superior and inferior vertebral body endplates. Generalized osteosclerosis in ADO typically results from abnormalities in osteoclast function, due most commonly to mutations in the chloride channel 7 (CLCN7) gene. A variety of debilitating complications can occur over time due to bone fragility, impingement of cranial nerves, encroachment of osteopetrotic bone in the marrow space, and poor bone vascularity. There is a wide spectrum of disease phenotype, even within the same family. Currently, there is no disease specific treatment for ADO, so clinical care focuses on monitoring for disease complications and symptomatic treatment. This review describes the history of ADO, the wide disease phenotype, and potential new therapies.

Osteopetrosis: Discovery and early history of "marble bone disease"

Discovery in 1904 of the disorder initially called "marble bones", then in 1926 more appropriately referred to as "osteopetrosis", is attributed to Heinrich E. Albers-Schönberg (1865-1921), the first radiologist. He used the new technique of Röntgenography to report in a young man the radiographic hallmarks of this osteopathy. Clinical descriptions of lethal forms of osteopetrosis had apparently been published earlier by others. Here, I review the discovery and early understanding of osteopetrosis. Characterization of this disorder commencing at the beginning of the past century would support the aphorism of Sir William Osler (1849-1919): "Clinics Are Laboratories; Laboratories Of The Highest Order". As featured in this special issue of Bone, the osteopetroses would prove remarkably informative about the formation and function of the cells responsible for skeletal resorption.

Skeletal phenotypes in secreted frizzled-related protein 4 gene knockout mice mimic skeletal architectural abnormalities in subjects with Pyle's disease from SFRP4 mutations

Mutations in SFRP4 cause Pyle's bone disease with wide metaphyses and increased skeletal fragility. The WNT signaling pathway plays important roles in determining skeletal architecture and SFRP4 is a secreted Frizzled decoy receptor that inhibits WNT signaling. Seven cohorts of male and female Sfrp4 gene knockout mice, examined through 2 years of age, had a normal lifespan but showed cortical and trabecular bone phenotypes. Mimicking human Erlenmeyer flask deformities, bone cross-sectional areas were elevated 2-fold in the distal femur and proximal tibia but only 30% in femur and tibia shafts. Reduced cortical bone thickness was observed in the vertebral body, midshaft femur and distal tibia. Elevated trabecular bone mass and numbers were observed in the vertebral body, distal femur metaphysis and proximal tibia metaphysis. Midshaft femurs retained extensive trabecular bone through 2 years of age. Vertebral bodies had increased compressive strength, but femur shafts had reduced bending strength. Trabecular, but not cortical, bone parameters in heterozygous Sfrp4 mice were modestly affected. Ovariectomy resulted in similar declines in both cortical and trabecular bone mass in wild-type and Sfrp4 KO mice. SFRP4 is critical for metaphyseal bone modeling involved in determining bone width. Sfrp4 KO mice show similar skeletal architecture and bone fragility deficits observed in patients with Pyle's disease with SFRP4 mutations.

Spectrum of Skeletal Imaging Features in Osteopetrosis: Inheritance Pattern and Radiological Associations

Osteopetrosis (from the Greek "osteo": bone; "petrosis": stone) is a clinically and genetically heterogeneous group of rare diseases of the skeleton, sharing the same main characteristic of an abnormally increased bone density. Dense bones in radiological studies are considered the hallmark of these diseases, and the reason for the common term used: "Marble bone disease". Interestingly, a radiologist, Dr. Albers-Schonberg, described this disease for the first time in Germany in 1904. Indeed, radiology has a key role in the clinical diagnosis of osteopetrosis and is fundamental in assessing the disease severity and complications, as well as in follow-up controls and the evaluation of the response to treatment. Osteopetrosis includes a broad spectrum of genetic mutations with very different clinical symptoms, age onset, and prognosis (from mild to severe). This diversity translates into different imaging patterns related to specific mutations, and different disease severity. The main recognized types of osteopetrosis are the infantile malignant forms with autosomal recessive transmission (ARO-including the rarer X-linked recessive form); the intermediate autosomal recessive form (IAO); and the autosomal dominant ones ADO, type I, and type II, the latter being called 'Albers-Schonberg' disease. Imaging features may change among those distinct types with different patterns, severities, skeletal segment involvement, and speeds of progression. There are several classical and well-recognized radiological features related to osteopetrosis: increased bone density (all types with different degrees of severity assuming a 'Marble Bone Appearance' especially in the ARO type), different metaphyseal alterations/enlargement including the so-called 'Erlenmeyer flask deformity' (particularly of femoral bones, more frequent in ADO type 2, and less frequent in ARO and IAO), 'bone in bone' appearance (more frequent in ADO type 2, less frequent in ARO and IAO), and 'rugger-jersey spine' appearance (typical of ADO type 2). After conducting an overview of the epidemiological and clinical characteristic of the disease, this review article aims at summarizing the main radiological features found in different forms of osteopetrosis together with their inheritance pattern.

Hereditary Metabolic Bone Diseases: A Review of Pathogenesis, Diagnosis and Management

Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases. In this review, we examine 25 selected hereditary metabolic bone diseases and recognized genetic variations of 78 genes that represent each of the three groups, including sclerosing bone disorders, disorders of defective bone mineralization and disorder of bone matrix and cartilage formation. We also review pathophysiology, manifestation and treatment for each disease. Advances in molecular genetics and basic sciences has led to accurate genetic diagnosis and novel effective therapeutic strategies for some diseases. For other diseases, the genetic basis and pathophysiology remain unclear. Further researches are therefore crucial to innovate ways to overcome diagnostic challenges and develop effective treatment options for these orphan diseases.

Craniofacial, dental, and molecular features of Pyle disease in a South African child

Introduction

Pyle Disease (PD), or familial metaphyseal dysplasia [OMIM 265900], is a rare autosomal recessive condition leading to widened metaphyses of long bones and cortical bone thinning and genu valgum. We detail the oro-dental and molecular findings in a South African patient with PD.

Methods

The patient underwent clinical, radiographic and molecular examinations. An exfoliated tooth was analysed using scanning electron microscopy and was compared to a control tooth.

Results

The patient presented with marked Erlenmeyer-flask deformity (EFD) of the long bones and several Wormian bones. His dental development was delayed by approximately three years. The permanent molars were mesotaurodontic. The bones, including the jaws and cervical vertebrae, showed osteoporotic changes. The lamina dura was absent, and the neck of the condyle lacked normal constrictions. Ionic component analysis of the primary incisors found an absence of magnesium. Sanger sequencing revealed a novel putative pathogenic variant in intron 5 of SFRP4 (c.855+4delAGTA) in a homozygous state.

Conclusion

This study has reported for the first time the implication of a mutation in the SFRP4 gene in an African patient presenting with PD and highlights the need for dental practitioners to be made aware of the features and management implications of PD.

Wnt signaling pathway inhibitors, sclerostin and DKK-1, correlate with pain and bone pathology in patients with Gaucher disease

Patients with Gaucher disease (GD) have progressive bone involvement that clinically presents with debilitating bone pain, structural bone changes, bone marrow infiltration (BMI), Erlenmeyer (EM) flask deformity, and osteoporosis. Pain is referred by the majority of GD patients and continues to persist despite the type of therapy. The pain in GD is described as chronic deep penetrating pain; however, sometimes, patients experience severe acute pain. The source of bone pain is mainly debated as nociceptive pain secondary to bone pathology or neuropathic or inflammatory origins. Osteocytes constitute a significant source of secreted molecules that coordinate bone remodeling. Osteocyte markers, sclerostin (SOST) and Dickkopf-1 (DKK-1), inactivate the canonical Wnt signaling pathway and lead to the inhibition of bone formation. Thus, circulated sclerostin and DKK-1 are potential biomarkers of skeletal abnormalities. This study aimed to assess the circulating levels of sclerostin and DKK-1 in patients with GD and their correlation with clinical bone pathology parameters: pain, bone mineral density (BMD), and EM deformity. Thirty-nine patients with GD were classified into cohorts based on the presence and severity of bone manifestations. The serum levels of sclerostin and DKK-1 were quantified by enzyme-linked immunosorbent assays. The highest level of sclerostin was measured in GD patients with pain, BMI, and EM deformity. The multiparameter analysis demonstrated that 95% of GD patients with pain, BMI, and EM deformity had increased levels of sclerostin. The majority of patients with elevated sclerostin also have osteopenia or osteoporosis. Moreover, circulating sclerostin level increase with age, and GD patients have elevated sclerostin levels when compared with healthy control from the same age group. Pearson's linear correlation analysis showed a positive correlation between serum DKK-1 and sclerostin in healthy controls and GD patients with normal bone mineral density. However, the balance between sclerostin and DKK-1 waned in GD patients with osteopenia or osteoporosis. In conclusion, the osteocyte marker, sclerostin, when elevated, is associated with bone pain, BMI, and EM flask deformity in GD patients. The altered sclerostin/DKK-1 ratio correlates with the reduction of bone mineral density. These data confirm that the Wnt signaling pathway plays a role in GD-associated bone disease. Sclerostin and bone pain could be used as biomarkers to assess patients with a high risk of BMI and EM flask deformities.

Cortical bone development, maintenance and porosity: genetic alterations in humans and mice influencing chondrocytes, osteoclasts, osteoblasts and osteocytes

Cortical bone structure is a crucial determinant of bone strength, yet for many years studies of novel genes and cell signalling pathways regulating bone strength have focused on the control of trabecular bone mass. Here we focus on mechanisms responsible for cortical bone development, growth, and degeneration, and describe some recently described genetic-driven modifications in humans and mice that reveal how these processes may be controlled. We start with embryonic osteogenesis of preliminary bone structures preceding the cortex and describe how this structure consolidates then matures to a dense, vascularised cortex containing an increasing proportion of lamellar bone. These processes include modelling-induced, and load-dependent, asymmetric cortical expansion, which enables the cortex's transition from a highly porous woven structure to a consolidated and thickened highly mineralised lamellar bone structure, infiltrated by vascular channels. Sex-specific differences emerge during this process. With aging, the process of consolidation reverses: cortical pores enlarge, leading to greater cortical porosity, trabecularisation and loss of bone strength. Each process requires co-ordination between bone formation, bone mineralisation, vascularisation, and bone resorption, with a need for locational-, spatial- and cell-specific signalling pathways to mediate this co-ordination. We will discuss these processes, and a number of cell-signalling pathways identified in both murine and human genetic studies to regulate cortical bone mass, including signalling through gp130, STAT3, PTHR1, WNT16, NOTCH, NOTUM and sFRP4.

Imaging of Congenital Skeletal Disorders

Osteochondrodysplasias are the result of the expression of gene mutations. The phenotypes in osteochondrodysplasias evolve through life, with the possibility that previously unaffected bones may be involved at later stages of growth. Due to the variable time of onset, the diagnosis may be made prenatally, at birth, or later. Certainty in the diagnosis is sometimes only achieved as the patient matures and the disease evolves. Radiographic evaluation is a fundamental part of the diagnostic work-up of congenital skeletal disorders and in most cases the first tool used to arrive at a diagnosis. This review describes the imaging characteristics, specific signs, and evolution of several skeletal dysplasias in which diagnosis may be directly or indirectly suggested by radiologic findings. A definitive accurate diagnosis of a congenital skeletal abnormality is necessary to help provide a prognosis of expected outcomes and to counsel parents and patients.

Natural history of alpha-thalassemia X-linked intellectual disability syndrome: A case report of a 45-year-old man

We have followed the clinical course of a 45-year-old man with a severe form of alpha-thalassemia X-linked intellectual disability syndrome for 40 years. The most challenging health issue is the combination of rumination, drooling, and vomiting. The patient achieved present adaptive and motor skills in his teenage years. He is able to move on the floor in a sitting position. He seems happy and has not shown any behavioral or psychiatric symptoms. New signs not described in the literature before are accelerated growth after puberty and atypical sleeping position with upper body resting on legs.

Improving the quantitative classification of Erlenmeyer flask deformities

The Erlenmeyer flask deformity is a common skeletal modeling deformity, but current classification systems are binary and may restrict its utility as a predictor of associated skeletal conditions. A quantifiable 3-point system of severity classification could improve its predictive potential in disease. Ratios were derived from volumes of regions of interests drawn in 50 Gaucher's disease patients. ROIs were drawn from the distal physis to 2 cm proximal, 2 cm to 4 cm, and 4 cm to 6 cm. Width was also measured at each of these boundaries. Two readers rated these 100 femurs using a 3-point scale of severity classification. Weighted kappa indicated reliability and one-way analysis of variance characterized ratio differences across the severity scale. Accuracy analyses allowed determination of clinical cutoffs for each ratio. Pearson's correlations assessed the associations of volume and width with a shape-based concavity metric of the femur. The volume ratio incorporating the metaphyseal region from 0 to 2 cm and the diametaphyseal region at 4-6 cm was most accurate at distinguishing femurs on the 3-point scale. Receiver operating characteristic curves for this ratio indicated areas of 0.95 to distinguish normal and mild femurs and 0.93 to distinguish mild and severe femurs. Volume was moderately associated with the degree of femur concavity. The proposed volume ratio method is an objective, proficient method at distinguishing severities of the Erlenmeyer flask deformity with the potential for automation. This may have application across diseases associated with the deformity and deficient osteoclast-mediated modeling of growing bone.

Bilateral Posterior-Stabilized Total Knee Arthroplasty in a Patient With Osteopetrosis and Literature Review

We present a case report of a patient with osteopetrosis and refractory bilateral knees osteoarthritis who underwent bilateral total knee arthroplasties (TKAs). After conservative management has failed, surgical treatment with arthroplasty is an excellent alternative with satisfactory outcomes. TKA in patients with osteopetrosis has only been described in 6 other case studies, none of which underwent bilateral TKA. To perform this procedure, additional attention should be directed toward the presurgical planning because of the amplified difficulty of the procedure and the altered bone biology that increases the risks of intraoperative fractures and markedly extends the time of surgery. This report describes a case of osteopetrosis with refractory osteoarthritis managed with bilateral TKA, the surgical technique and special considerations, complications, and future recommendations.

A family of Melnick-Needles syndrome: a case report

BACKGROUND

Melnick-Needles syndrome (MNS) is an extremely rare osteochondrodysplasia caused by a mutation of FLNA, the gene encoding filamin A. MNS is inherited in an X-linked dominant manner. In this study, we describe three members of the same family with MNS, who exhibited different phenotypic severity despite having an identical FLNA gene mutation.

CASE PRESENTATION

The patient was 16 months old, with a history of delayed physical development, multiple upper respiratory infections and otitis media episodes. She was referred to our orthopedic clinic because of bowed legs and an abnormal plain chest radiograph. Both upper and lower extremities were bowed. Plain X-rays showed thoracolumbar kyphoscoliosis, with anterior and posterior vertebral scalloping, and thin, wavy ribs. Hypoplasia of the pubis and ischium, with bilateral coxa valga, were also noted. Target exome sequencing revealed a heterozygous mutation of FLNA, c.3578 T > C, p.Lys1193Pro, which confirmed the diagnosis of MNS. Her older sister and mother had minimal deformities of the axial and extremity skeleton, but genetic analyses revealed the same FLNA mutation as the patient. The mutation identified in this family has not been previously reported.

CONCLUSION

This report illustrates the potential inherited nature of MNS and the phenotypic variability of clinicoradiologic characteristics. In patients with traits suggestive of MNS, a careful medical and family history should be obtained, and genetic testing should be performed for the patient, as well as all family members.

Diagnosis and management of pediatric metabolic bone diseases associated with skeletal fragility

PURPOSE OF REVIEW

The goal of this review is to give an overview of diagnosis and up-to-date management of major pediatric metabolic bone diseases that are associated with bone fragility, including nutritional rickets, hypophosphatemic rickets, osteogenesis imperfecta, Ehlers--Danlos syndrome, Marfan's syndrome, hypophosphatasia, osteopetrosis and skeletal fluorosis.

RECENT FINDINGS

During the past decade, a number of advanced treatment options have been introduced and shown to be an effective treatment in many metabolic bone disorders, such as burosumab for hypophosphatemic rickets and asfotase alfa for hypophosphatasia. On the other hand, other disorders, such as nutritional rickets and skeletal fluorosis continue to be underrecognized in many regions of the world. Genetic disorders of collagen-elastin, such as osteogenesis imperfecta, Ehlers--Danlos syndrome and Marfan's syndrome are also associated with skeletal fragility, which can be misdiagnosed as caused by non-accidental trauma/child abuse.

SUMMARY

It is essential to provide early and accurate diagnosis and treatment for pediatric patients with metabolic bone disorders in order to maintain growth and development as well as prevent fractures and metabolic complications.

Massive osteopetrosis caused by non-functional osteoclasts in R51Q SNX10 mutant mice

The R51Q mutation in sorting nexin 10 (SNX10) was shown to cause a lethal genetic disease in humans, namely autosomal recessive osteopetrosis (ARO). We describe here the first R51Q SNX10 knock-in mouse model and show that mice homozygous for this mutation exhibit massive, early-onset, and widespread osteopetrosis. The mutant mice exhibit multiple additional characteristics of the corresponding human disease, including stunted growth, failure to thrive, missing or impacted teeth, occasional osteomyelitis, and a significantly-reduced lifespan. Osteopetrosis in this model is the result of osteoclast inactivity that, in turn, is caused by absence of ruffled borders in the mutant osteoclasts and by their inability to secrete protons. These results confirm that the R51Q mutation in SNX10 is a causative factor in ARO and provide a model system for studying this rare disease.

The Implications of Endocrinology in Orthodontics – Literature Review

Endocrinopathies have a variety of orofacial presentations which span from dental malocclusion to facial disfigurement. These characteristics depend on the nature and severity of the condition. An orthodontist should understand the body’s physiological processes to be able to timely determine the optimum intervention and plan treatment stages accordingly in compromised individuals. Communication between the two specialties should be well coordinated and should help facilitate quality health care to the patient. This review was aimed to impart the basic knowledge and the pivotal guidelines for orthodontic management in these conditions. Systemic conditions require multidisciplinary management and the dental team should aim to provide quality oral health care to enhance the overall quality of life and the orthodontist plays a vital role in helping patients achieve physical and psychological health.

Imaging of non-neuronopathic Gaucher disease: recent advances in quantitative imaging and comprehensive assessment of disease involvement

Gaucher disease is an inherited metabolic disorder resulting in deficiency of lysosomal enzyme β-glucocerebrosidase causing the accumulation of abnormal macrophages (“Gaucher cells”) within multiple organs, most conspicuously affecting the liver, spleen, and bone marrow. As the most common glycolipid metabolism disorder, it is important for radiologists encountering these patients to be familiar with advances in imaging of organ and bone marrow involvement and understand the role of imaging in clinical decision-making. The recent advent of commercially available, reliable, and reproducible quantitative MRI acquisitions to measure fat fractions prompts revisiting the role of quantitative assessment of bone marrow involvement. This manuscript reviews the diverse imaging manifestations of Gaucher disease and discusses more optimal quantitative approaches to ascertain solid organ and bone marrow involvement with an emphasis on future applications of other quantitative methods including elastography.

Novel CLCN7 mutations cause autosomal dominant osteopetrosis type II and intermediate autosomal recessive osteopetrosis

Osteopetrosis refers to a group of rare genetic bone diseases that are clinically characterized by increased bone mass and fragility. The principal pathogenic defect in patients with chloride channel 7 (CLCN7) gene‑dependent osteopetrosis is reduced osteoclast activity, which leads to decreased bone resorption. Mutations in the CLCN7 gene result in autosomal dominant osteopetrosis type II (ADO‑II), autosomal recessive osteopetrosis (ARO) and intermediate ARO (IARO). In the present study, eight mutations in the CLCN7 gene were identified in six patients with familial osteopetrosis and one patient with sporadic osteopetrosis. Heterozygous mutations c.856C>T (R286W), c.2236T>G (Y746D), c.296A>G (Y99C) and c.937G>A (E313K), and a splice mutation (c.2232‑2A>G) in the CLCN7 gene were detected in patients with ADO‑II. A homozygous mutation c.2377G>C (G793R), and a compound heterozygous mutation c.1409C>T (P470L) and c.647_648dupTG (K217X) were detected in two Chinese families with IARO. Among these mutations, two heterozygous mutations (c.2236T>G and c.2232‑2A>G), one homozygous mutation (c.2377G>C) and the compound heterozygous mutation (c.1409C>T and c.647_648dupTG) are novel, to the best of our knowledge. The present findings not only broaden the allelic spectrum of CLCN7 mutations, but also provide increased knowledge of the clinical phenotypes observed in Chinese patients with osteopetrosis.

Profilin 1 Negatively Regulates Osteoclast Migration in Postnatal Skeletal Growth, Remodeling, and Homeostasis in Mice

Profilin 1 (Pfn1), a regulator of actin polymerization, controls cell movement in a context-dependent manner. Pfn1 supports the locomotion of most adherent cells by assisting actin-filament elongation, as has been shown in skeletal progenitor cells in our previous study. However, because Pfn1 has also been known to inhibit migration of certain cells, including T cells, by suppressing branched-end elongation of actin filaments, we hypothesized that its roles in osteoclasts may be different from that of osteoblasts. By investigating the osteoclasts in culture, we first verified that Pfn1-knockdown (KD) enhances bone resorption in preosteoclastic RAW264.7 cells, despite having a comparable number and size of osteoclasts. Pfn1-KD in bone marrow cells showed similar results. Mechanistically, Pfn1-KD osteoclasts appeared more mobile than in controls. In vivo, the osteoclast-specific conditional Pfn1-deficient mice (Pfn1-cKO) by CathepsinK-Cre driver demonstrated postnatal skeletal phenotype, including dwarfism, craniofacial deformities, and long-bone metaphyseal osteolytic expansion, by 8 weeks of age. Metaphyseal and diaphyseal femurs were drastically expanded with suppressed trabecular bone mass as indicated by μCT analysis. Histologically, TRAP-positive osteoclasts were increased at endosteal metaphysis to diaphysis of Pfn1-cKO mice. The enhanced movement of Pfn1-cKO osteoclasts in culture was associated with a slight increase in cell size and podosome belt length, as well as an increase in bone-resorbing activity. Our study, for the first time, demonstrated that Pfn1 has critical roles in inhibiting osteoclast motility and bone resorption, thereby contributing to essential roles in postnatal skeletal homeostasis. Our study also provides novel insight into understanding skeletal deformities in human disorders.

Gaucher Disease: New Expanded Classification Emphasizing Neurological Features

Gaucher disease (GD) is a rare inherited metabolic disorder and the most common lysosomal storage disorder, caused by a deficiency in glucocerebrosidase enzyme activity. It has been classified according to the neurological manifestations into three types: type 1, without neuropathic findings, type 2 with acute infantile neuropathic signs and type 3 or chronic neuropathic form. However, report of new variants has led to the expansion of phenotype as a clinical phenotype of GD considered as a continuum of phenotypes. Therefore, it seems that a new classification is needed to cover new forms of the disease.

Diagnosis and Management of Osteopetrosis: Consensus Guidelines From the Osteopetrosis Working Group

BACKGROUND

Osteopetrosis encompasses a group of rare metabolic bone diseases characterized by impaired osteoclast activity or development, resulting in high bone mineral density. Existing guidelines focus on treatment of the severe infantile forms with hematopoietic cell transplantation (HCT) but do not address the management of patients with less severe forms for whom HCT is not the standard of care. Therefore, our objective was to develop expert consensus guidelines for the management of these patients.

METHODS

A modified Delphi method was used to build consensus among participants of the Osteopetrosis Working Group, with responses to an anonymous online survey used to identify areas of agreement and conflict and develop a follow-up survey. The strength of recommendations and quality of evidence was graded using the Grading of Recommendations Assessment, Development and Evaluation system.

RESULTS

Consensus was found in the areas of diagnosis, monitoring, and treatment. We recommend relying on characteristic radiographic findings to make the diagnosis and found that genetic testing adds important information by identifying mutations associated with unique disease complications. We recommend ongoing monitoring for changes in mineral metabolism and other complications, including cranial nerve impingement, anemia, leukopenia, and dental disease. We suggest that calcitriol should not be used in high doses and instead recommend symptom-based supportive therapy for disease complications because noninfantile osteopetrosis has no effective treatment.

CONCLUSIONS

Scarcity of published studies on osteopetrosis reduce the ability to develop evidence-based guidelines for the management of these patients. Expert opinion-based guidelines for this rare condition are nevertheless important to enable improved care.

A Review of Gaucher Disease Pathophysiology, Clinical Presentation and Treatments

Gaucher disease (GD, ORPHA355) is a rare, autosomal recessive genetic disorder. It is caused by a deficiency of the lysosomal enzyme, glucocerebrosidase, which leads to an accumulation of its substrate, glucosylceramide, in macrophages. In the general population, its incidence is approximately 1/40,000 to 1/60,000 births, rising to 1/800 in Ashkenazi Jews. The main cause of the cytopenia, splenomegaly, hepatomegaly, and bone lesions associated with the disease is considered to be the infiltration of the bone marrow, spleen, and liver by Gaucher cells. Type-1 Gaucher disease, which affects the majority of patients (90% in Europe and USA, but less in other regions), is characterized by effects on the viscera, whereas types 2 and 3 are also associated with neurological impairment, either severe in type 2 or variable in type 3. A diagnosis of GD can be confirmed by demonstrating the deficiency of acid glucocerebrosidase activity in leukocytes. Mutations in the GBA1 gene should be identified as they may be of prognostic value in some cases. Patients with type-1 GD-but also carriers of GBA1 mutation-have been found to be predisposed to developing Parkinson's disease, and the risk of neoplasia associated with the disease is still subject to discussion. Disease-specific treatment consists of intravenous enzyme replacement therapy (ERT) using one of the currently available molecules (imiglucerase, velaglucerase, or taliglucerase). Orally administered inhibitors of glucosylceramide biosynthesis can also be used (miglustat or eliglustat).

Can acetazolamide be used to treat diseases involving increased bone mineral density?

Sclerosing bone dysplasias are a series of clinically and genetically heterogeneous diseases characterized by functional failure of the osteoclasts in bone resorption, leading to an excessive amount of bone mineral density (BMD) which could have serious clinical consequences. We treated three children affected with seriously high levels of BMD with acetazolamide, with the intention of inducing metabolic acidosis, thus increasing bone resorption and reducing BMD. All our patients tolerated and followed the treatment well and the clinical response was satisfactory in all cases.

The etiology and significance of fractures in infants and young children: a critical multidisciplinary review

This paper addresses significant misconceptions regarding the etiology of fractures in infants and young children in cases of suspected child abuse. This consensus statement, supported by the Child Abuse Committee and endorsed by the Board of Directors of the Society for Pediatric Radiology, synthesizes the relevant scientific data distinguishing clinical, radiologic and laboratory findings of metabolic disease from findings in abusive injury. This paper discusses medically established epidemiology and etiologies of childhood fractures in infants and young children. The authors also review the body of evidence on the role of vitamin D in bone health and the relationship between vitamin D and fractures. Finally, the authors discuss how courts should properly assess, use, and limit medical evidence and medical opinion testimony in criminal and civil child abuse cases to accomplish optimal care and protection of the children in these cases.

Metaphyseal dysplasia associated with chronic facial nerve palsy

INTRODUCTION

Metaphyseal dysplasia (Pyle disease) is a rare autosomal recessive disease with impressive and characteristic radiological findings but relatively mild clinical features. It is usually incidentally diagnosed, despite the impressive radiological findings of gross metaphyseal widening and thinning of cortical bone.

CASE REPORT

Herein, we report an exceptionally unusual case of metaphyseal dysplasia in association with chronic facial nerve palsy.

DISCUSSION

Chronic facial nerve palsy due to compression of the facial nerve in a patient with Pyle disease represents an unusual novelty. Furthermore, this case delineates the clinical spectrum and phenotype of such a rare clinical entity. To the best of our knowledge, this is the first time that such an association is being described.

A case of infantile osteopetrosis: The radioclinical features with literature update

BACKGROUND

Osteopetrosis is a rare hereditary metabolic bone disorder characterized by generalized skeletal sclerosis caused by a defect in bone resorption and remodelling. Infantile autosomal recessive osteopetrosis is one of three subtypes of osteopetrosis and the most severe form. The correct and early diagnosis of infantile osteopetrosis is important for management of complications and for future genetic counselling. Diagnosis is largely based on clinical and radiographic evaluation, confirmed by gene testing where applicable.

METHODS

Therefore, in this case study the classical clinical and radiological signs of a boy with infantile osteopetrosis will be presented with a comprehensive literature update. The differentiating signs from other causes of hereditary osteosclerosing dysplasias are discussed.

RESULTS

This case study and review of available literature show that there tends to be a highly unique clinical and skeletal radiographic pattern of affection in infantile osteopetrosis.

CONCLUSION

Although tremendous advances have been made in the elucidation of the genetic defect of osteopetrosis over the past years, the role of accurate clinical and radiological assessment remains an important contributor to the diagnosis of infantile osteopetrosis.

Osteochondromas in fibrodysplasia ossificans progressiva: a widespread trait with a streaking but overlooked appearance when arising at femoral bone end

Metaphyseal bony outgrowths are a well-recognized feature of fibrodysplasia ossificans progressiva (FOP) phenotype, but its genuine frequency, topographic distribution, morphological aspect, and potential implications are not fully established. To better ascertain the frequency and characteristics of osteocartilaginous exostoses in FOP disease, we conducted a cross-sectional radiological study based on all the traceable cases identified in a previous comprehensive national research. Metaphyseal exostoses were present in all the 17 cases of FOP studied. Although most often arising from the distal femoral (where metaphyseal exostoses adopt a peculiar not yet reported appearance) and proximal tibial bones, we have found that they are not restricted to these areas, but rather can be seen scattered at a variety of other skeletal sites. Using nuclear magnetic resonance imaging, we show that these exophytic outgrowths are true osteochondromas. As a whole, these results are in agreement with data coming from the literature review. Our study confirms the presence of metaphyseal osteochondromas as a very frequent trait of FOP phenotype and an outstanding feature of its anomalous skeletal developmental component. In line with recent evidences, this might imply that dysregulation of BMP signaling, in addition to promoting exuberant heterotopic ossification, could induce aberrant chondrogenesis and osteochondroma formation. Unveiling the molecular links between these physiopathological pathways could help to illuminate the mechanisms that govern bone morphogenesis.

Rapid skeletal turnover in a radiographic mimic of osteopetrosis

Among the high bone mass disorders, the osteopetroses reflect osteoclast failure that prevents skeletal resorption and turnover, leading to reduced bone growth and modeling and characteristic histopathological and radiographic findings. We report an 11-year-old boy with a new syndrome that radiographically mimics osteopetrosis (OPT), but features rapid skeletal turnover. He presented at age 21 months with a parasellar, osteoclast-rich giant cell granuloma. Radiographs showed a dense skull, generalized osteosclerosis and cortical thickening, medullary cavity narrowing, and diminished modeling of tubular bones. His serum alkaline phosphatase was >5000 IU/L (normal <850 IU/L). After partial resection, the granuloma re-grew but then regressed and stabilized during 3 years of uncomplicated pamidronate treatment. His hyperphosphatasemia transiently diminished, but all bone turnover markers, especially those of apposition, remained elevated. Two years after pamidronate therapy stopped, bone mineral density (BMD) Z-scores reached +9.1 and +5.8 in the lumbar spine and hip, respectively, and iliac crest histopathology confirmed rapid bone remodeling. Serum multiplex biomarker profiling was striking for low sclerostin. Mutation analysis was negative for activation of lipoprotein receptor-related protein 4 (LRP4), LRP5, or TGFβ1, and for defective sclerostin (SOST), osteoprotegerin (OPG), RANKL, RANK, SQSTM1, or sFRP1. Microarray showed no notable copy number variation. Studies of his nonconsanguineous parents were unremarkable. The etiology and pathogenesis of this unique syndrome are unknown.

Gaucher disease and bone manifestations

Gaucher disease is a relatively rare metabolic disease caused by the inherited deficiency of the lysosomal enzyme glucocerebrosidase. Gaucher disease affects multiple organs, among which is the skeleton. Bone involvement occurs frequently in Gaucher disease, and is one of its most debilitating features, reducing the quality of life of patients. Bone status is an important consideration for treatment to ameliorate symptoms and reduce the risk of irreversible complications. We have conducted a systematic review of all the various aspects of Gaucher disease, focusing on different skeletal manifestations, pathophysiology of bone alterations, clinical symptoms, and current diagnostic and therapeutic approaches.

Early diagnosis of Gaucher disease in pediatric patients: proposal for a diagnostic algorithm

Gaucher disease (GD) is caused by an enzyme deficiency that leads to the accumulation of glycolipids in various organs. Although the signs and symptoms of GD emerge in childhood in the majority of patients, the disease often remains unrecognized for many years with delay of benefits of therapy or development of irreversible complications. Based on published data and data from the International Collaborative Gaucher Group Registry, an algorithm has been drafted for early diagnosis of GD in pediatric patients. It will help hematologists in promoting a timely diagnosis and early access to therapy for pediatric patients with GD.

Skeletal dysplasias: A radiographic approach and review of common non-lethal skeletal dysplasias

Skeletal dysplasias are not uncommon entities and a radiologist is likely to encounter a suspected case of dysplasia in his practice. The correct and early diagnosis of dysplasia is important for management of complications and for future genetic counselling. While there is an exhaustive classification system on dysplasias, it is important to be familiar with the radiological features of common dysplasias. In this article, we enumerate a radiographic approach to skeletal dysplasias, describe the essential as well as differentiating features of common non-lethal skeletal dysplasias and conclude by presenting working algorithms to either definitively diagnose a particular dysplasia or suggest the most likely differential diagnoses to the referring clinician and thus direct further workup of the patient.

Miscellaneous non-inflammatory musculoskeletal conditions. Gaucher disease and bone

Gaucher disease (GD) is an inherited lysosomal storage disorder affecting multiple organs. Non-neuronopathic GD, the most common form, can present with hepatosplenomegaly, anaemia, bleeding tendencies, thrombocytopenia, skeletal pathologies, growth retardation and, in severe cases, with pulmonary disease. The bone manifestations include bone infarcts, avascular bone necrosis, lytic lesions, osteosclerosis, fractures due to osteoporosis and, rarely, acute osteomyelitis. Bone pain of varying intensity, fractures and joint collapses increase the patients' morbidity and impair their mobility and quality of life. Currently available therapies - enzyme replacement therapy and substrate reduction therapy - have shown to improve blood count and the visceral manifestations within a short time. Beneficial effects have also been documented on bone pain, bone crises and the extent of osteoporosis. The article focusses on the bone pathologies of GD including its pathophysiology, current diagnostics, clinical management and therapeutic effects of enzyme replacement therapy, substrate reduction therapy and bone-specific therapies.

Dysosteosclerosis presents as an "osteoclast-poor" form of osteopetrosis: comprehensive investigation of a 3-year-old girl and literature review

Dysosteosclerosis (DSS), an extremely rare dense bone disease, features short stature and fractures and sometimes optic atrophy, cranial nerve palsy, developmental delay, and failure of tooth eruption in infancy or early childhood consistent with osteopetrosis (OPT). Bone histology during childhood shows unresorbed primary spongiosa from deficient osteoclast action. Additionally, there is remarkable progressive flattening of all vertebrae and, by adolescence, paradoxical metaphyseal osteopenia with thin cortical bone. Reports of consanguinity indicate autosomal recessive inheritance, yet more affected males than females suggest X-linked recessive inheritance. We investigated a nonconsanguineous girl with DSS. Osteosclerosis was discovered at age 7 months. Our studies, spanning ages 11 to 44 months, showed weight at approximately 50th percentile, and length diminishing from approximately 30th percentile to -2.3 SD. Head circumference was +4 SD. The patient had frontal bossing, blue sclera, normal teeth, genu valgum, and unremarkable joints. Radiographs showed orbital and facial sclerosis, basilar thickening, bone-in-bone appearance of the pelvis, sclerotic long bone ends, and fractures of ribs and extremities. Progressive metaphyseal widening occurred as vertebrae changed from ovoid to flattened and became beaked anteriorly. A hemogram was normal. Consistent with OPT, serum parathyroid hormone (PTH) concentrations reflected dietary calcium levels. Serum bone alkaline phosphatase, osteocalcin, and TRACP-5b were subnormal. The iliac crest contained excessive primary spongiosa and no osteoclasts. No mutations were identified in the splice sites or exons for the genes encoding chloride channel 7, T-cell immune regulator 1, OPT-associated transmembrane protein 1, and monocyte colony-stimulating factor (M-CSF) and its receptor C-FMS, ANKH, OPG, RANK, and RANKL. Genomic copy-number microarray was unrevealing. Hence, DSS is a distinctive OPT of unknown etiology featuring osteoclast deficiency during early childhood. How osteopenia follows is an enigma of human skeletal pathobiology.

Mutational analysis of two boys with the severe perinatally lethal Melnick-Needles syndrome

Melnick-Needles syndrome (MNS) (OMIM 309350) is a rare, X-linked dominant condition, caused by mutations in the filamin A gene (FLNA, on Xq28). In females, the syndrome presents with bone dysplasia and characteristic facial changes. Affected males may show two different phenotypes. One is similar to the female phenotype and is seen in children born to unaffected mothers and suggesting new mutations. Alternatively, males born to affected mothers have an embryonic or perinatally lethal disorder. It has been claimed that MNS constitutes part of a spectrum including frontometaphyseal dysplasia, otopalatodigital syndrome type 1 (OPD1) and otopalatodigital syndrome type 2 (OPD2). These conditions are produced by different mutations in the filamin A gene (FLNA). MNS is caused by three different mutations in FLNA exon 22, to date detected only in females. We describe the clinical manifestations and present the results of FLNA exon 22 mutations screening in two boys with the perinatally lethal form of MNS and their affected mothers. In order to obtain DNA amplification from paraffin-embedded tissues, we designed a new method based on hemi-nested PCR. One of the children (and his mother) had a previously undescribed mutation produced by a double SNP in the positions 3776 and 3777 of the gene and leading to an amino acid substitution (NP_001447:p.[Gly1176Asp]). The second child (and his mother) had an already known mutation (NP_001447.2:p[.Ser1199Leu]). This is the first report confirming the presence FLNA mutations in boys with the perinatally lethal phenotype of MNS. (

RANKL inhibition improves bone properties in a mouse model of osteogenesis imperfecta

Recently, a new class of agents targeting the receptor activator of nuclear factor-kappaB ligand (RANKL) pathway has been developed for the treatment of osteoporosis and other bone diseases. In the current study, inhibition of the RANKL pathway was evaluated to assess effects on "bone quality" and fracture incidence in an animal model of osteogenesis imperfect (OI), the oim/oim mouse. Juvenile oim/oim ( approximately 6 weeks old) and wildtype (+/+) mice were treated with either a RANKL inhibitor (RANK-Fc) or saline. After treatment, bone density increased significantly in the femurs of both genotypes. Femoral length decreased with RANK-Fc in +/+ mice. Geometric measurements at mid-diaphysis in the oim/oim groups showed increases in the ML periosteal and endosteal diameters and AP cortical thickness in the treated groups. Within +/+ groups, ML cortical thickness and ML femoral periosteal diameter were significantly increased with RANK-Fc. Biomechanical testing revealed increased stiffness in oim/oim and +/+ mice. Total strain was increased with treatment in the +/+ mice. Histologically, RANKL inhibition resulted in retained growth plate cartilage in both genotypes. The average number of fractures sustained by RANK-Fc-treated oim/oim mice was not significantly decreased compared to saline treated oim/oim mice. This preclinical study demonstrated that RANKL inhibition at the current dose improved density and some geometric and biomechanical properties of oim/oim bone, but it did not decrease fracture incidence. Further studies that address commencement of therapy at earlier time points are needed to determine whether this mode of therapy will be clinically useful in OI.