International nosology and classification of constitutional disorders of bone (2001)

Multicentric Osteolysis Nodulosis Arthropathy Syndrome Simulating Juvenile Idiopathic Arthritis in an Adult Female: A Case Report and a Literature Review

Multicentric osteolysis, nodulosis, and arthropathy (MONA) syndrome is one of the rare genetic skeletal dysplasias, inherited as an autosomal recessive disorder, which predominantly involves carpal and tarsal bones with characteristic osteolytic lesions and can be misdiagnosed as juvenile idiopathic arthritis or rheumatoid arthritis. MONA syndrome includes diseases involving two genes: the matrix metalloproteinase 2 (MMP2) gene and matrix metalloproteinase 14 (MMP14). Both genes are assumed to cause phenotype variants of the same disease. Older patients may manifest some arthritic features, especially in the wrist, and minute pathological fractures can occur as well. These patients may be misdiagnosed as inflammatory arthritis and physicians might prescribe corticosteroid and disease-modifying immunosuppressive agents. Therefore, physicians should carefully evaluate genetic skeletal dysplasia to make a correct diagnosis and avoid unnecessary pharmacological intervention. We report a case of MONA syndrome in an adult female who came to our facility for an intensive rehabilitation program.

Nosology of genetic skeletal disorders: 2023 revision

The "Nosology of genetic skeletal disorders" has undergone its 11th revision and now contains 771 entries associated with 552 genes reflecting advances in molecular delineation of new disorders thanks to advances in DNA sequencing technology. The most significant change as compared to previous versions is the adoption of the dyadic naming system, systematically associating a phenotypic entity with the gene it arises from. We consider this a significant step forward as dyadic naming is more informative and less prone to errors than the traditional use of list numberings and eponyms. Despite the adoption of dyadic naming, efforts have been made to maintain strong ties to the MIM catalog and its historical data. As with the previous versions, the list of disorders and genes in the Nosology may be useful in considering the differential diagnosis in the clinic, directing bioinformatic analysis of next-generation sequencing results, and providing a basis for novel advances in biology and medicine.

Novel Pathogenetic Variants in PTHLH and TRPS1 Genes Causing Syndromic Brachydactyly

Skeletal disorders, including both isolated and syndromic brachydactyly type E, derive from genetic defects affecting the fine tuning of the network of pathways involved in skeletogenesis and growth-plate development. Alterations of different genes of this network may result in overlapping phenotypes, as exemplified by disorders due to the impairment of the parathyroid hormone/parathyroid hormone-related protein pathway, and obtaining a correct diagnosis is sometimes challenging without a genetic confirmation. Five patients with Albright's hereditary osteodystrophy (AHO)-like skeletal malformations without a clear clinical diagnosis were analyzed by whole-exome sequencing (WES) and novel potentially pathogenic variants in parathyroid hormone like hormone (PTHLH) (BDE with short stature [BDE2]) and TRPS1 (tricho-rhino-phalangeal syndrome [TRPS]) were discovered. The pathogenic impact of these variants was confirmed by in vitro functional studies. This study expands the spectrum of genetic defects associated with BDE2 and TRPS and demonstrates the pathogenicity of TRPS1 missense variants located outside both the nuclear localization signal and the GATA ((A/T)GATA(A/G)-binding zinc-containing domain) and Ikaros-like binding domains. Unfortunately, we could not find distinctive phenotypic features that might have led to an earlier clinical diagnosis, further highlighting the high degree of overlap among skeletal syndromes associated with brachydactyly and AHO-like features, and the need for a close interdisciplinary workout in these rare patients. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Overlapping Phenotypes in Osteopetrosis and Pycnodysostosis in Asian-Indians

Osteopetrosis is a disorder characterized by high bone density, hepatosplenomegaly, visual and hearing loss, and anemia. Pycnodysostosis presents with short stature, acroosteolysis, and dense bones. We, hereby, present here a family with autosomal dominant osteopetrosis and also children with recessive osteopetrosis and pycnodysostosis. The molecular confirmation was done in 3 cases. Genetic heterogeneity in clinical presentation is discussed here. Further studies will help in identifying epigenetic alterations and population-specific variants and also developing targeted therapies.

New Structural and Single Nucleotide Mutations in Type I and Type II Collagens in Taiwanese Children With Type I and Type II Collagenopathies

Collagenopathy is a rare genetic condition characterized by abnormality in either collagen structure or metabolism. Variations in its clinical presentations highlight diversity in the genetic causes and potential existence of concurrent mutations. Through whole exome sequencing (WES) complemented with multiplex ligation-dependent probe amplification, we identified the genetic etiologies for six cases with osteogenesis imperfecta (OI) in COL1A1 (p.T1298N, p.Q1280Pfs^∗51, and p.G557Vfs^∗23) and COL1A2 (c.1-1677_133-441del) as well as three cases with spondyloepiphyseal dysplasia congenita in COL2A1 (p.G1041S, p.G654S, and p.G441A). Co-occurrence of COL1A1 and WNT1 mutations was found in a patient with a mild OI phenotype but severe osteoporosis. These findings extended the pathogenic variant spectrum of COL1A1, COL1A2, and COL2A1 for type I and type II collagenopathies. Although WES provides a fast and accurate method to identify the genetic causes in most of the patients with type I and type II collagenopathies, its limitation of detecting CNVs because of variable capturing uniformity should be kept in mind when interpreting the results. Taken together, we demonstrate that multiple genetic characterizing technologies can provide an accurate and efficient molecular diagnostic of new genetic variants in disease-causing genes that are compatible with clinical phenotypes.

Anatomical Considerations of Embryology and Development of the Musculoskeletal System: Basic Notions for Musculoskeletal Radiologists

The musculoskeletal (MSK) system begins to form in the third week of intrauterine development. Multiple genes are involved in the complex different processes to form the skeleton, muscles and joints. The embryonic period, from the third to the eighth week of development, is critical for normal development and therefore the time when most structural defects are induced. Many of these defects have a genetic origin, but environmental factors may also play a very important role. This review summarizes the embryology of the different components of the MSK system and their configuration as an organ-system, analyzes the clinical implications resulting from failures in the process of organogenesis, and describes the first approach to diagnosis of skeletal abnormalities using prenatal ultrasound.

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.

Managing challenging pain and irritability in OSTM1 mutation-related infantile malignant osteopetrosis

Osteopetrosis describes a heterogeneous group of diseases characterised by increased bone density due to impaired osteoclast. The malignant infantile autosomal recessive (MIOP) form caused by mutations in OSTM1 is the most severe form of osteopetrosis. Children with this phenotype exhibit multisystemic complications, of which the neuropathic manifestations are the most severe. Infants with MIOP may present with pain and irritability that are likely to become continuous and debilitating as the disease progresses. There is limited understanding of the aetiology and management of pain in MIOP. Here, we describe a 2 month-old infant with OSTM1 mutation-related MIOP presenting with severe irritability and pain. This case provides the opportunity to discuss the cause and management of these distressing symptoms. We also review similar cases and the possible underlying mechanisms of pain and irritability to help provide a conceptual framework for the management of these symptoms in infants with OSTM1 MIOP.

BMPR1B gene in brachydactyly type 2-A family with de novo R486W mutation and a disease phenotype

Background

Brachydactylies are a group of inherited conditions, characterized mainly by the presence of shortened fingers and toes. Based on the patients’ phenotypes, brachydactylies have been subdivided into 10 subtypes. In this study, we have identified a family with two members affected by brachydactyly type A2 (BDA2). BDA2 is caused by mutations in three genes: BMPR1B, BMP2 or GDF5. So far only two studies have reported the BDA2 cases caused by mutations in the BMPR1B gene.

Methods

We employed next‐generation sequencing to identify mutations in culpable genes.

Results and Conclusion

In this paper, we report a case of BDA2 resulting from the presence of a heterozygous c.1456C>T, p.Arg486Trp variant in BMPR1B, which was previously associated with BDA2. The next generation sequencing analysis of the patients’ family revealed that the mutation occurred de novo in the proband and was transmitted to his 26‐month‐old son. Although the same variant was confirmed in both patients, their phenotypes were different with more severe manifestation of the disease in the adult.

The evolution of the nosology of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a relatively common genetic skeletal disorder with an estimated frequency of 1 in 20 000 worldwide. The manifestations are diverse and although individually rare, the several different forms contribute to the production of a significant number of affected individuals with considerable morbidity and mortality. During the last decade, there have been extensive molecular investigations into the etiology of OI and these advances have direct relevance to the medical management of the disorder, and the purpose of this review is to document the history and evolution of the nosology of OI. The current nosology, based on molecular concepts, which are crucial in the identification of genotype-phenotype correlations in persons with OI, is also outlined. The successive revisions of the nosology and classification of OI have highlighted the importance of the nomenclature of the condition in order for it to be recognized by clinicians, scientists and patient advocacy groups. In this way, improved counseling of patients and individualized, tailored therapeutic approaches based on the underlying pathophysiology of the individual's type of OI have been facilitated.

Results of growth-friendly management of early-onset scoliosis in children with and without skeletal dysplasias

Aims

The aim of this study was to compare the surgical and quality-of-life outcomes of children with skeletal dysplasia to those in children with idiopathic early-onset scoliosis (EOS) undergoing growth-friendly management.

Patients and Methods

A retrospective review of two prospective multicentre EOS databases identified 33 children with skeletal dysplasia and EOS (major curve ≥ 30°) who were treated with growth-friendly instrumentation at younger than ten years of age, had a minimum two years of postoperative follow-up, and had undergone three or more lengthening procedures. From the same registries, 33 matched controls with idiopathic EOS were identified. A total of 20 children in both groups were treated with growing rods and 13 children were treated with vertical expandable prosthetic titanium rib (VEPTR) instrumentation.

Results

Mean preoperative major curves were 76° (34° to 115°) in the skeletal dysplasia group and 75° (51° to 113°) in the idiopathic group (p = 0.55), which were corrected at final follow-up to 49° (13° to 113°) and 46° (12° to 112°; p = 0.68), respectively. T1-S1 height increased by a mean of 36 mm (0 to 105) in the skeletal dysplasia group and 38 mm (7 to 104) in the idiopathic group at the index surgery (p = 0.40), and by 21 mm (1 to 68) and 46 mm (7 to 157), respectively, during the distraction period (p = 0.0085). The skeletal dysplasia group had significantly worse scores in the physical function, daily living, financial impact, and parent satisfaction preoperatively, as well as on financial impact and child satisfaction at final follow-up, than the idiopathic group (all p < 0.05). The domains of the 24-Item Early-Onset Scoliosis Questionnaire (EOSQ24) remained at the same level from preoperative to final follow-up in the skeletal dysplasia group (all p > 0.10).

Conclusion

Children with skeletal dysplasia gained significantly less spinal growth during growth-friendly management of their EOS and their health-related quality of life was significantly lower both preoperatively and at final follow-up than in children with idiopathic EOS. Cite this article: Bone Joint J 2019;101-B:1563–1569

Nosology and classification of genetic skeletal disorders: 2019 revision

The application of massively parallel sequencing technology to the field of skeletal disorders has boosted the discovery of the underlying genetic defect for many of these diseases. It has also resulted in the delineation of new clinical entities and the identification of genes and pathways that had not previously been associated with skeletal disorders. These rapid advances have prompted the Nosology Committee of the International Skeletal Dysplasia Society to revise and update the last (2015) version of the Nosology and Classification of Genetic Skeletal Disorders. This newest and tenth version of the Nosology comprises 461 different diseases that are classified into 42 groups based on their clinical, radiographic, and/or molecular phenotypes. Remarkably, pathogenic variants affecting 437 different genes have been found in 425/461 (92%) of these disorders. By providing a reference list of recognized entities and their causal genes, the Nosology should help clinicians achieve accurate diagnoses for their patients and help scientists advance research in skeletal biology.

MR Imaging of Fetal Musculoskeletal Disorders

This article outlines the main findings in prenatal musculoskeletal disorders. Three main technologies are generally used to obtain images within the uterus during pregnancy: ultrasound (US), MR imaging, and computed tomography (CT). Currently, the primary imaging method used for fetal assessment during pregnancy is US because it is patient friendly, useful, cost-effective, and (considered) safe. MR imaging is generally performed when US yields equivocal results because it offers additional information about fetal abnormalities and conditions in situations in which US is unable to provide high-quality images.

A de novo variant in MMP13 identified in a patient with dominant metaphyseal anadysplasia

Metaphyseal anadysplasia 1 (MIM# 602111) belongs to a heterogeneous group of skeletal diseases characterized by an autosomal dominant form of growth defects due to metaphyseal changes with epiphyseal involvement similar to other metaphyseal disorders. Matrix metalloproteinase 13 encoded by MMP13 presumably plays important roles in bone formation and growth, and pathogenic variants in MMP13 have been identified to cause metaphyseal anadysplasia 1. Only six pathogenic variants in MMP13 have been previously reported worldwide. The genotype-phenotype correlation of MMP13-related disorders has not been fully understood. Here we reported the identification of a previously unreported pathogenic heterozygous de novo variant NM_002427.3:c.212T > C/p.Met71Thr in MMP13 in a Chinese male pediatric patient with metaphyseal anadysplasia 1 and additional phenotypes, including mild rickets-like changes observed on upper long bone metaphyses and patchy bone defects on the spine vertebrae particularly resolved by childhood. Our findings not only expand genotype and phenotype spectrums of MMP13-related disorders but also offer further information for precise diagnosis and classification of metaphyseal anadysplasia disorders.

Expanding the phenome and variome of skeletal dysplasia

PURPOSE

To describe our experience with a large cohort (411 patients from 288 families) of various forms of skeletal dysplasia who were molecularly characterized.

METHODS

Detailed phenotyping and next-generation sequencing (panel and exome).

RESULTS

Our analysis revealed 224 pathogenic/likely pathogenic variants (54 (24%) of which are novel) in 123 genes with established or tentative links to skeletal dysplasia. In addition, we propose 5 genes as candidate disease genes with suggestive biological links (WNT3A, SUCO, RIN1, DIP2C, and PAN2). Phenotypically, we note that our cohort spans 36 established phenotypic categories by the International Skeletal Dysplasia Nosology, as well as 18 novel skeletal dysplasia phenotypes that could not be classified under these categories, e.g., the novel C3orf17-related skeletal dysplasia. We also describe novel phenotypic aspects of well-known disease genes, e.g., PGAP3-related Toriello-Carey syndrome-like phenotype. We note a strong founder effect for many genes in our cohort, which allowed us to calculate a minimum disease burden for the autosomal recessive forms of skeletal dysplasia in our population (7.16E-04), which is much higher than the global average.

CONCLUSION

By expanding the phenotypic, allelic, and locus heterogeneity of skeletal dysplasia in humans, we hope our study will improve the diagnostic rate of patients with these conditions.

[Characterization of patients with skeletal genetic diseases in a Colombian referral center]

INTRODUCTION

Short height in Colombia has an estimated prevalence of 10%. The 2009 Nosology and Classification of Skeletal Genetic Diseases described 456 clinical conditions using biochemical, molecular and radiological criteria for diagnosis.

OBJECTIVE

To analyze demographic, epidemiological and clinical variables in a group of patients with skeletal genetic diseases referred to the Instituto de Ortopedia Infantil Roosevelt.

MATERIALS AND METHODS

Patients referred between 2008 and 2014 were analyzed filtering 167 diagnoses of the International Classification of Diseases, 10th revision (ICD 10), related to skeletal genetic diseases. Demographic, epidemiological and clinical variables were explored using descriptive statistics. An intervention score was generated contemplating different combinations of treatments. An inferential statistical analysis using Student's t test was performed on such variables.

RESULTS

The most frequent reason for consultation was suspicion of a genetic skeletal disorder. The types of treatments considered included support, surgical, pharmacological and orthotics, and it was established that genetic skeletal disorders were associated with higher intervention scores while tall and short height showed a lower score.

CONCLUSIONS

Most referred patients were classified with genetic bone diseases, short stature and other monogenic genetic diseases. Significant differences were found between the age at symptoms onset and the age of diagnosis. Diversity was found in the therapeutic approach among different groups of pathologies. Patients with tall and short height showed lower intervention scores, which may warn on the need to reassess the therapeutic requirements of these groups.

Infantile osteopetrosis associated with osteomyelitis

Osteopetrosis is a rare inherited disorder characterised by the inability to reabsorb and remodel bone due to an osteoclast dysfunction. An increase in bone mass and density results in severe skeletal malformation and bone marrow failure, which may be fatal. The aim of this study was to report a case of infantile osteopetrosis in a 6-year-old boy, who primarily complained of dental problems. The patient developed an osteomyelitis after a primary tooth extraction. We also reviewed the literature about this genetic bone disease, since the management of dental problems of these patients can be a challenge to the dentist. The diagnosis, clinical and radiographic features and treatment of the case were discussed in this work.

Increased classical endoplasmic reticulum stress is sufficient to reduce chondrocyte proliferation rate in the growth plate and decrease bone growth

Mutations in genes encoding cartilage oligomeric matrix protein and matrilin-3 cause a spectrum of chondrodysplasias called multiple epiphyseal dysplasia (MED) and pseudoachondroplasia (PSACH). The majority of these diseases feature classical endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) as a result of misfolding of the mutant protein. However, the importance and the pathological contribution of ER stress in the disease pathogenesis are unknown. The aim of this study was to investigate the generic role of ER stress and the UPR in the pathogenesis of these diseases. A transgenic mouse line (ColIITg^cog) was generated using the collagen II promoter to drive expression of an ER stress-inducing protein (Tg^cog) in chondrocytes. The skeletal and histological phenotypes of these ColIITg^cog mice were characterised. The expression and intracellular retention of Tg^cog induced ER stress and activated the UPR as characterised by increased BiP expression, phosphorylation of eIF2α and spliced Xbp1. ColIITg^cog mice exhibited decreased long bone growth and decreased chondrocyte proliferation rate. However, there was no disruption of chondrocyte morphology or growth plate architecture and perturbations in apoptosis were not apparent. Our data demonstrate that the targeted induction of ER stress in chondrocytes was sufficient to reduce the rate of bone growth, a key clinical feature associated with MED and PSACH, in the absence of any growth plate dysplasia. This study establishes that classical ER stress is a pathogenic factor that contributes to the disease mechanism of MED and PSACH. However, not all the pathological features of MED and PSACH were recapitulated, suggesting that a combination of intra- and extra-cellular factors are likely to be responsible for the disease pathology as a whole.

Upper cervical spine fusion in children with skeletal dysplasia

BACKGROUND

Skeletal dysplasias have been associated with upper cervical instability. Many patients are initially asymptomatic, but the instability may progress to subluxation and dislocation and complications thereof, including death. Surgery is hampered by petite osseous structures and low bone formation rate.

AIM

To review the outcomes of surgical fusion of upper cervical instability in children with rare skeletal dysplasias.

MATERIAL AND METHODS

A retrospective study of eight children with five different rare skeletal dysplasias needing upper cervical instrumented stabilization. Cases were evaluated for clinical, radiologic, and quality-of-life outcomes, with median follow-up time of 5 years.

RESULTS

Six patients underwent posterior, segmental cervical spine instrumentation and fusion (three C1/C2 fusions, three occipitocervical fusions), one anterior cervical instrumented spinal fusion, and one anteroposterior fusion. Autogenous bone grafting was used in all patients, and seven were immobilized using a halo body jacket. Nonunion in occipitocervical fusions was common in these patients (3/8 patients). Rib autograft from occiput to cervical spine with recombinant human BMP-2 was used to salvage nonunions.

CONCLUSIONS

Surgical fixation in the pediatric cervical spine is hampered by fragile posterior structures. A postoperative immobilization by halo vest for 4 months is customary. Selective anterior corpectomy and plate fixation is not recommended in pediatric patients with skeletal dysplasias.

LEVEL OF EVIDENCE

Level 4, Case Series.

Perinatal Diagnostic Approach to Fetal Skeletal Dysplasias: Six Years Experience of a Tertiary Center

Skeletal dysplasias (SDs) constitute a group of heterogeneous disorders affecting growth morphology of the chondro-osseous tissues. Prenatal diagnosis of SD is a considerable clinical challenge due to phenotypic variability. We performed a retrospective analysis of the fetal autopsies series conducted between January 2006 and December 2012 at our center. SD was detected in 54 (10%) out of 542 fetal autopsy cases which included; 11.1% thanatophoric dysplasia (n = 6), 7.4% achondroplasia (n = 4), 3.7% osteogenesis imperfect (n = 2), 1.9% Jarcho-Levin Syndrome (n = 1), 1.9% arthrogryposis (n = 1), 1.9% Dyggve-Melchior-Clausen syndrome (n = 1), 72.1% of dysostosis cases (n = 39). All SD cases were diagnosed by ultrasonography. In 20 of the cases, amniocentesis was performed, 4 cases underwent molecular genetic analyses. Antenatal identification of dysplasia is important in the management of pregnancy and in genetic counseling. Our data analysis showed that SD is usually detected clinically after the 20th gestational week. Genetic analyses for SD may provide early diagnosis and management.

Fetal skeletal dysplasias in a tertiary care center: radiology, pathology, and molecular analysis of 112 cases

Fetal skeletal dysplasias are a heterogeneous group of rare genetic disorders, affecting approximately 2.4-4.5 of 10,000 births. We performed a retrospective review of the perinatal autopsies conducted between the years 2002-2011 at our center. The study population consisted of fetuses diagnosed with skeletal dysplasia with subsequent termination, stillbirth and live-born who died shortly after birth. Of the 2002 autopsies performed, 112 (5.6%) were diagnosed with skeletal dysplasia. These 112 cases encompassed 17 of 40 groups of Nosology 2010. The two most common Nosology groups were osteogenesis imperfecta [OI, 27/112 (24%)] and the fibroblast growth factor receptor type 3 (FGFR3) chondrodysplasias [27/112 (24%)]. The most common specific diagnoses were thanatophoric dysplasia (TD) type 1 [20 (17.9%)], and OI type 2 [20 (17.9%)]. The combined radiology, pathology, and genetic investigations and grouping the cases using Nosology 2010 resulted in a specific diagnosis in 96 of 112 cases.

Brachydactyly E: isolated or as a feature of a syndrome

Brachydactyly (BD) refers to the shortening of the hands, feet or both. There are different types of BD; among them, type E (BDE) is a rare type that can present as an isolated feature or as part of more complex syndromes, such as: pseudohypopthyroidism (PHP), hypertension with BD or Bilginturan BD (HTNB), BD with mental retardation (BDMR) or BDE with short stature, PTHLH type. Each syndrome has characteristic patterns of skeletal involvement. However, brachydactyly is not a constant feature and shows a high degree of phenotypic variability. In addition, there are other syndromes that can be misdiagnosed as brachydactyly type E, some of which will also be discussed. The objective of this review is to describe some of the syndromes in which BDE is present, focusing on clinical, biochemical and genetic characteristics as features of differential diagnoses, with the aim of establishing an algorithm for their differential diagnosis. As in our experience many of these patients are recruited at Endocrinology and/or Pediatric Endocrinology Services due to their short stature, we have focused the algorithm in those steps that could mainly help these professionals.

Thanatophoric dysplasia: autopsy findings over a 25-year period

The aim of our study was to retrospectively assess morphological findings in thanatophoric dysplasia, particularly, in how many cases were cerebral manifestations with temporal lobe dysplasia identified. We also wanted to register and analyze the proportions between lung, brain, and body weight. Criteria for inclusion were an autopsy performed during the period ranging from 1985 to 2009 with a diagnosis of thanatophoric dysplasia. During a 25-year period 25 cases of thanatophoric dysplasia were registered. Temporal lobe dysplasia was recognized in 52% of the cases, and after 1998 temporal lobe dysplasia was described in all cases. In 19 cases the brain/body weight ratio was increased, and in all cases the lung/body weight ratio was below the corresponding ratio calculated according to standard measurements. In all but one case the ratio of brain to lung weight was increased. This study focuses on morphological findings, stressing the importance of temporal lobe dysplasia in confirming a diagnosis of thanatophoric dysplasia. Lung/body, brain/body, and brain/lung weight ratios confirm macrocephaly and lung hypoplasia, which are constant findings in cases involving thanatophoric dysplasia. Femur and brain morphology inclusive histology remains the ultimate tool for confirmation of this lethal condition, although it has to be seen in a context inclusive of radiological examination.

Infantile osteopetrosis with superimposed rickets

BACKGROUND

Rickets is a complication of infantile osteopetrosis and pre-treatment recognition of this complication is important.

OBJECTIVE

To describe four children with infantile osteopetrosis complicated by rickets (osteopetrorickets) and review the relevant literature.

MATERIALS AND METHODS

Retrospective chart analysis of four infants with osteopetrorickets and a systematic review of the relevant literature.

RESULTS

We saw five children with infantile osteopetrosis, of whom four had superimposed rickets, for a period of 12 years. The review of the literature (including the current four children), yielded 20 children with infantile osteopetrorickets. The children ranged in age from 2 months to 12 months. In all children, hepatosplenomegaly was found. Sixteen (80%) children had visual impairments and eight (40%) children had hearing impairments. Serum calcium-phosphorus product was less than 30 in 18 children (90%). Twelve children (60%) were hypocalcemic and 18 (90%) were hypophosphatemic. In all children, the radiological examination demonstrated diffuse bony sclerosis and metaphyseal splaying and fraying of long bones. Five children (25%) had pathological fracture of extremities and 15 (75%) had rachitic rosary.

CONCLUSION

Rickets as a complication to infantile osteopetrosis is not uncommon. Skeletal roentgenograms are of critical importance in the diagnosis of both osteopetrosis and superimposed rickets.

Idiopathic multicentric osteolysis: upper extremity manifestations and surgical considerations during childhood

PURPOSE

Idiopathic multicentric osteolysis (IMO) is an uncommon disease presenting during childhood with resorption of the carpus and tarsus with nephropathy. The few case reports and literature reviews do not focus on the upper extremity disease manifestations or surgical treatment options. We review our experience with the upper extremity in IMO.

METHODS

We evaluated 8 affected children, specifically assessing early disease manifestations, misdiagnoses, radiographic progression, and surgical treatments rendered.

RESULTS

Wrist pain and swelling are typically the first manifestations of IMO. Characteristic upper extremity findings, once the disease has progressed, include metacarpophalangeal joint hyperextension, wrist ulnar deviation and flexion, and loss of elbow extension. Radiographically, there is osteolysis of the carpus and proximal metacarpals with resorption of the elbow joint in some patients. Surgical treatments, including soft tissue release with pinning or joint arthrodesis, may offer pain relief and improve alignment, but outcomes are inconsistent.

CONCLUSIONS

Children with IMO are almost always misdiagnosed initially, and the correct diagnosis may be delayed by years. The hand surgeon is ideally suited to provide an accurate diagnosis of IMO, because wrist pain and swelling and thumb interphalangeal joint contracture are common early manifestations.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

The fate of the hip in spondylo-epi-metaphyseal dysplasia: clinical and radiological evaluation of adults with SEMD Handigodu type

PURPOSE

This study was undertaken to document the fate of the hip with reference to its structure and function in patients with spondylo-epi-metaphyseal dysplasia tarda Handigodu type (SEMD(HG)).

MATERIAL AND METHODS

Radiographs of 271 adult patients with SEMD(HG) were studied to identify the pattern of long-term sequelae in the hips. Several measurements of the proximal femur and acetabulum were made to quantify morphological alterations in the hip. Fifty-four adult patients were examined and administered a questionnaire to evaluate the extent of disability attributable to the hips.

RESULTS

Three patterns of changes in the hips were noted: 35% had acetabular protrusio, 33% had subluxation of the hip, and 32% had no protrusio or subluxation. Distinctly different anthropometric measurements and dimensional alterations around the hip were noted in these three patterns. Patients with protrusio were relatively tall while those with subluxation were the shortest. All the patients had developed degenerative arthritis of the hips by the fourth decade of life irrespective of the pattern of hip involvement. The reduction in the range of hip motion and fixed deformities were most severe in patients with protrusio. All the patients had significant disability and very low functional hip scores.

CONCLUSION

Degenerative arthritis of the hip develops in the majority of patients with SEMD(HG); the symptoms are severe enough to warrant reconstructive surgery by the fourth decade of life. Protrusio or subluxation develops in a third of the patients each; both these complications will influence the surgical approach if total hip arthroplasty is planned.

Co-clustering phenome-genome for phenotype classification and disease gene discovery

Understanding the categorization of human diseases is critical for reliably identifying disease causal genes. Recently, genome-wide studies of abnormal chromosomal locations related to diseases have mapped >2000 phenotype–gene relations, which provide valuable information for classifying diseases and identifying candidate genes as drug targets. In this article, a regularized non-negative matrix tri-factorization (R-NMTF) algorithm is introduced to co-cluster phenotypes and genes, and simultaneously detect associations between the detected phenotype clusters and gene clusters. The R-NMTF algorithm factorizes the phenotype–gene association matrix under the prior knowledge from phenotype similarity network and protein–protein interaction network, supervised by the label information from known disease classes and biological pathways. In the experiments on disease phenotype–gene associations in OMIM and KEGG disease pathways, R-NMTF significantly improved the classification of disease phenotypes and disease pathway genes compared with support vector machines and Label Propagation in cross-validation on the annotated phenotypes and genes. The newly predicted phenotypes in each disease class are highly consistent with human phenotype ontology annotations. The roles of the new member genes in the disease pathways are examined and validated in the protein–protein interaction subnetworks. Extensive literature review also confirmed many new members of the disease classes and pathways as well as the predicted associations between disease phenotype classes and pathways.

Rituximab resistant evans syndrome and autoimmunity in Schimke immuno-osseous dysplasia

Autoimmunity is often observed among individuals with primary immune deficiencies; however, the frequency and role of autoimmunity in Schimke immuno-osseous dysplasia (SIOD) has not been fully assessed. SIOD, which is caused by mutations of SMARCAL1, is a rare autosomal recessive disease with its prominent features being skeletal dysplasia, T cell deficiency, and renal failure. We present a child with severe SIOD who developed rituximab resistant Evans syndrome (ES). Consistent with observations in several other immunodeficiency disorders, a review of SIOD patients showed that approximately a fifth of SIOD patients have some features of autoimmune disease. To our best knowledge this case represents the first patient with SIOD and rituximab resistant ES and the first study of autoimmune disease in SIOD.

FGFR3 related skeletal dysplasias diagnosed prenatally by ultrasonography and molecular analysis: presentation of 17 cases

Fibroblast Growth Factor Receptor 3 (FGFR3) related skeletal dysplasias are caused by mutations in the FGFR3 gene that result in increased activation of the receptors causing alterations in the process of endochondral ossification in all long bones, and include achondroplasia, hypochondroplasia, thanatophoric dysplasia, and SADDAN. Reports of prenatal diagnosis of FGFR3 related skeletal dysplasias are not rare; however, the correlation between 2nd trimester ultrasonographic findings and underlying molecular defect in these cases is relatively poor. There is a need for specific ultrasound (U/S) predictors than can distinguish lethal from non-lethal cases and aid an earlier prenatal diagnosis. Here we present one familial and 16 sporadic cases with FGFR3 related skeletal dysplasia, and we evaluate biometric parameters and U/S findings consistent with the diagnosis of skeletal dysplasia. U/S scan performed even at the 18th week of gestation can indicate a decreased rate of development of the femora (femur length (FL) <5th centile), while the mean gestational age at diagnosis is still around the 26th week. The utility of other biometric parameters and ratios is discussed (foot length, BPD, HC, FL/foot, and FL/AC). Prenatal cytogenetic and molecular genetic analyses were performed. A final diagnosis was reached by molecular analysis. In two cases of discontinued pregnancy, fetal autopsy led to a phenotypic diagnosis and confirmed the prenatal prediction of lethality. We conclude that the combination of U/S and molecular genetic approach is helpful for establishing an accurate diagnosis of FGFR3-related skeletal dysplasias in utero and subsequently for appropriate genetic counselling and perinatal management.

Identification and molecular characterization of two novel mutations in COL1A2 in two Chinese families with osteogenesis imperfecta

Osteogenesis imperfecta (OI, also known as brittle bone disease) is caused mostly by mutations in two type I collagen genes, COL1A1 and COL1A2 encoding the pro-α1 (I) and pro-α2 (I) chains of type I collagen, respectively. Two Chinese families with autosomal dominant OI were identified and characterized. Linkage analysis revealed linkage of both families to COL1A2 on chromosome 7q21.3-q22.1. Mutational analysis was carried out using direct DNA sequence analysis. Two novel missense mutations, c.3350A>G and c.3305G>C, were identified in exon 49 of COL1A2 in the two families, respectively. The c.3305G>C mutation resulted in substitution of a glycine residue (G) by an alanine residue (A) at codon 1102 (p.G1102A), which was found to be mutated into serine (S), argine (R), aspartic acid (D), or valine (V) in other families. The c.3350A>G variant may be a de novo mutation resulting in p.Y1117C. Both mutations co-segregated with OI in respective families, and were not found in 100 normal controls. The G1102 and Y1117 residues were evolutionarily highly conserved from zebrafish to humans. Mutational analysis did not identify any mutation in the COX-2 gene (a modifier gene of OI). This study identifies two novel mutations p.G1102A and p.Y1117C that cause OI, significantly expands the spectrum of COL1A2 mutations causing OI, and has a significant implication in prenatal diagnosis of OI.

Nosology and classification of genetic skeletal disorders: 2010 revision

Genetic disorders involving the skeletal system arise through disturbances in the complex processes of skeletal development, growth and homeostasis and remain a diagnostic challenge because of their variety. The Nosology and Classification of Genetic Skeletal Disorders provides an overview of recognized diagnostic entities and groups them by clinical and radiographic features and molecular pathogenesis. The aim is to provide the Genetics, Pediatrics and Radiology community with a list of recognized genetic skeletal disorders that can be of help in the diagnosis of individual cases, in the delineation of novel disorders, and in building bridges between clinicians and scientists interested in skeletal biology. In the 2010 revision, 456 conditions were included and placed in 40 groups defined by molecular, biochemical, and/or radiographic criteria. Of these conditions, 316 were associated with mutations in one or more of 226 different genes, ranging from common, recurrent mutations to “private” found in single families or individuals. Thus, the Nosology is a hybrid between a list of clinically defined disorders, waiting for molecular clarification, and an annotated database documenting the phenotypic spectrum produced by mutations in a given gene. The Nosology should be useful for the diagnosis of patients with genetic skeletal diseases, particularly in view of the information flood expected with the novel sequencing technologies; in the delineation of clinical entities and novel disorders, by providing an overview of established nosologic entities; and for scientists looking for the clinical correlates of genes, proteins and pathways involved in skeletal biology. © 2011 Wiley-Liss, Inc.

A homozygous recurring mutation in WISP3 causing progressive pseudorheumatoid arthropathy

WISP3 is a member of the CCN (for CTGF, CYR61, and NOV) gene family, which encodes cysteine-rich secreted proteins with roles in cell growth and differentiation. Mutations in the WISP3 gene are associated with the autosomal recessive skeletal disorder, also known as progressive pseudorheumatoid arthropathy of childhood (PPAC). We diagnosed three siblings from a non-consanguineous family with PPAC. The patients were asymptomatic in early childhood. Signs and symptoms of disease that include progressive joint stiffness, swelling of the finger joints, and osteopenia, and slow linear growth developed between 2 and 8 years of age. PCR amplification and direct sequencing of the WISP3 gene revealed a homozygous mutation at nucleotide 156 of the WISP3 gene, resulting in a Cys52-to-ter substitution. This mutation has previously been reported in French, Italian, and Arab families. Interestingly, the C52X mutation was found to be associated with a c.248G-->A (G83E) variation, suggesting the existence of a founder effect. By contrast, the presence of the same aberration in three different ethnic groups could imply that this particular site is prone to mutation. Basal fasting concentrations of growth hormone, insulin-like growth factor-1, and insulin-like growth factor binding protein-3, as well as glucose and insulin levels revealed no aberrations. In conclusion, consideration of this rare disease that causes significant morbidity with short stature, osteopenia and arthritic complaints would prevent unnecessary examinations and treatment attempts. Testing for this specific mutation in suspected cases could provide a rapid and definitive diagnosis.

An unfolded protein response is the initial cellular response to the expression of mutant matrilin-3 in a mouse model of multiple epiphyseal dysplasia

Multiple epiphyseal dysplasia (MED) can result from mutations in matrilin-3, a structural protein of the cartilage extracellular matrix. We have previously shown that in a mouse model of MED the tibia growth plates were normal at birth but developed a progressive dysplasia characterised by the intracellular retention of mutant matrilin-3 and abnormal chondrocyte morphology. By 3 weeks of age, mutant mice displayed a significant decrease in chondrocyte proliferation and dysregulated apoptosis. The aim of this current study was to identify the initial post-natal stages of the disease. We confirmed that the disease phenotype is seen in rib and xiphoid cartilage and, like tibia growth plate cartilage is characterised by the intracellular retention of mutant matrilin-3. Gene expression profiling showed a significant activation of classical unfolded protein response (UPR) genes in mutant chondrocytes at 5 days of age, which was still maintained by 21 days of age. Interestingly, we also noted the upregulation of arginine-rich, mutated in early stage of tumours (ARMET) and cysteine-rich with EGF-like domain protein 2 (CRELD2) are two genes that have only recently been implicated in the UPR. This endoplasmic reticulum (ER) stress and UPR did not lead to increased chondrocyte apoptosis in mutant cartilage by 5 days of age. In an attempt to alleviate ER stress, mutant mice were fed with a chemical chaperone, 4-sodium phenylbutyrate (SPB). SPB at the dosage used had no effect on chaperone expression at 5 days of age but modestly decreased levels of chaperone proteins at 3 weeks. However, this did not lead to increased secretion of mutant matrilin-3 and in the long term did not improve the disease phenotype. We performed similar studies with a mouse model of Schmid metaphyseal chondrodysplasia, but again this treatment did not improve the phenotype.

Spondylo-epiphyseal dysplasia, Maroteaux type (pseudo-Morquio syndrome type 2), and parastremmatic dysplasia are caused by TRPV4 mutations

Recent discoveries have established the existence of a family of skeletal dysplasias caused by dominant mutations in TRPV4. This family comprises, in order of increasing severity, dominant brachyolmia, spondylo-metaphyseal dysplasia Kozlowski type, and metatropic dysplasia. We tested the hypothesis that a further condition, Spondylo-epiphyseal dysplasia (SED), Maroteaux type (MIM 184095; also known as pseudo-Morquio syndrome type 2), could be caused by TRPV4 mutations. We analyzed six individuals with Maroteaux type SED, including three who had previously been reported. All six patients were found to have heterozygous TRPV4 mutations; three patients had unreported mutations, while three patients had mutations previously described in association with metatropic dysplasia. In addition, we tested one individual with a distinct rare disorder, parastremmatic dysplasia (MIM 168400). This patient had a common, recurrent mutation seen in several patients with Kozlowski type spondylo-metaphyseal dysplasia. We conclude that SED Maroteaux type and parastremmatic dysplasia are part of the TRPV4 dysplasia family and that TRPV4 mutations show considerable variability in phenotypic expression resulting in distinct clinical-radiographic phenotypes.

Current themes in molecular pediatrics: molecular medicine and its applications

We focus on themes that are derived from clinical practice and research in the field of genetic diseases of bone and inborn errors of metabolism but may be of more general interest as they indicate some trends in molecular medicine as related to pediatrics. Identifying the disease-causing mechanism brings about efficient therapeutic strategies and discovering the mutant genotype in the near future may become helpful for devising custom-built molecular responses. At the same time, the transition of therapy from the experimental phase to industrial application is difficult as there may be novel roles (and potentially conflicting interests) between physicians, patient organisations, governmental agencies and the pharmaceutical industry. Awareness of these potential conflicts may help in recognizing and dealing with these issues.

Cranioectodermal dysplasia: a probable ciliopathy

Cranioectodermal dysplasia (CED), also known as Sensenbrenner syndrome, is a rare autosomal recessive genetic disorder characterized by typical craniofacial, skeletal and ectodermal defects, and tubulointerstitial nephritis leading to early end-stage renal failure. We report on a new familial case of a 9-year-old patient and two fetuses of 23 and 19 weeks of gestation respectively. Hypohidrosis was an additional ectodermal finding is the patient with CED. Postmortem findings in the two fetuses included acromesomelic shortening, craniofacial characteristics with absence of craniosynostosis, small kidneys with tubular and glomerular microscopic cysts, persistent ductal plate with portal fibrosis in the liver, small adrenals and roughly unremarkable histopathology of the physeal growth plate. Posterior fossa anomalies were additional findings in this patient and included an enlarged cisterna magna and a posterior fossa cyst. The above findings, in association with renal cysts, persistent ductal plate and portal fibrosis, introduce CED, a nonlethal genetic skeletal disorder of yet unknown molecular origin, as a possible member of the expanding group of ciliopathies.

A distinct form of spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL)-leptodactylic type: radiological characteristics in seven new patients

OBJECTIVE

This study presents seven cases of a rare but distinctive form of spondyloepimetaphyseal dysplasia with joint laxity-leptodactylic or Hall type to emphasize the characteristic clinical and radiological findings.

MATERIALS AND METHODS

A multiinstitutional retrospective review was performed on seven patients. The patient population consisted of one family with an affected mother and two siblings and four unrelated patients; there were one adult, aged 40 years, and six children, ranging in age from 3 to 12 years. The gender ratio of females to males was 5 to 2. We reviewed the clinical data and skeletal surveys and focused on radiographs of the pelvis, knees, hands, and spine.

RESULTS

The outstanding clinical features were short stature, midface hypoplasia, and multiple dislocations and/or ligamentous laxity of the large joints, particularly at the knees with a genu valgum or varum deformity. Of seven patients, six patients showed normal intellect but one patient had mild mental retardation. The main radiological features included small, irregular epiphyses, metaphyseal irregularity with vertical striations that was a constant finding at the knees, constricted femoral necks, delayed ossification of the carpal bones, and slender metacarpals. Progressive thoracolumbar scoliosis was evident with aging; however, the vertebral bodies appeared normal in height or mild platyspondyly was noted.

CONCLUSION

In view of the orthopedic management of multiple joint dislocations and ligamentous laxity of the large joints, awareness of this disease entity and diagnostic precision solely based on radiological findings is of importance, particularly as the disorder is currently more common than initially reported.

Guidelines for the prenatal diagnosis of fetal skeletal dysplasias

The osteochondrodysplasias, or skeletal dysplasias are a genetically heterogeneous group of over 350 distinct disorders, and many of them can present in the prenatal period as demonstrated by ultrasound. Differentiating these disorders in the prenatal period can be challenging because they are rare and many of the ultrasound findings are not necessarily pathognomic for a specific disorder. However, differentiating known lethal disorders from nonlethal disorders, providing differential diagnoses before delivery, determining postdelivery management plans and ultimately determining accurate recurrences risks to the at-risk couples improves patient care. These guidelines provide an approach to a fetus suspected of manifesting a skeletal dysplasia.

Genetic and orthopedic aspects of collagen disorders

PURPOSE OF REVIEW

'Collagens' are a family of structurally related proteins that play a wide variety of roles in the extracellular matrix. To date, there are at least 29 known types of collagen. Accordingly, abnormality in the various collagens produces a large category of diseases with heterogeneous symptoms. This review presents genetic and orthopedic aspects of type II, IX, and XI collagen disorders.

RECENT FINDINGS

Although a diverse group of conditions, mutation of collagens affecting the articular cartilage typically produces an epiphyseal skeletal dysplasia phenotype. Often, the ocular or auditory systems or both are also involved. Treatment of these collagenopathies is symptomatic and individualized. Study of tissue from animal models allows examination of mutation effects on the abnormal protein structure and function.

SUMMARY

The collagen superfamily comprises an important structural protein in mammalian connective tissue. Mutation of collagens produces a wide variety of genetic disorders, and those mutations affecting types II, IX, and XI collagens produce an overlapping spectrum of skeletal dysplasias. Findings range from lethal to mild, depending on the mutation of the collagen gene and its subsequent effect on the structure and/or metabolism of the resultant procollagen and/or collagen protein and its function in the body.

A novel matrix metalloproteinase 2 (MMP2) terminal hemopexin domain mutation in a family with multicentric osteolysis with nodulosis and arthritis with cardiac defects

Multicentric osteolysis with nodulosis and arthropathy (MONA, NAO (OMIM no. 605156)) is an autosomal recessive member of the 'vanishing bone' syndromes and is notable for the extent of carpal and tarsal osteolysis and interphalangeal joint erosions, facial dysmorphia, and the presence of fibrocollagenous nodules. This rare disorder has been described previously in Saudi Arabian and Indian families. We now report on the first Turkish family with MONA, further confirming the panethnic nature of this disease. Strikingly, and in addition to the previously noted skeletal and joint features, affected members of this family also had congenital heart defects. Molecular analysis identified a novel MMP2 inactivating mutation that deletes the terminal hemopexin domains and thus confirmed the diagnosis of MONA. On the basis of these findings, we suggest that cardiac defects may also represent a component of this syndrome and thus a physiologically relevant target of MMP-2 activity.

Dyggve-Melchior-Clausen syndrome: chondrodysplasia resulting from defects in intracellular vesicle traffic

Dyggve-Melchior-Clausen syndrome and Smith-McCort dysplasia are recessive spondyloepimetaphyseal dysplasias caused by loss-of-function mutations in dymeclin (Dym), a gene with previously unknown function. Here we report that Dym-deficient mice display defects in endochondral bone formation similar to that of Dyggve-Melchior-Clausen syndrome and Smith-McCort dysplasia, demonstrating functional conservation between the two species. Dym-mutant cells display multiple defects in vesicle traffic, as evidenced by enhanced dispersal of Golgi markers in interphase cells, delayed Golgi reassembly after brefeldin A treatment, delayed retrograde traffic of an endoplasmic reticulum-targeted Shiga toxin B subunit, and altered furin trafficking; and the Dym protein associates with multiple cellular proteins involved in vesicular traffic. These results establish dymeclin as a novel protein involved in Golgi organization and intracellular vesicle traffic and clarify the molecular basis for chondrodysplasia in mice and men.

Fetal skeletal dysplasia: an approach to diagnosis with illustrative cases

Skeletal dysplasias are a heterogeneous group of conditions associated with various abnormalities of the skeleton. These conditions are caused by widespread disturbance of bone growth, beginning during the early stages of fetal development and evolving throughout life. Despite recent advances in imaging, fetal skeletal dysplasias are difficult to diagnose in utero due to a number of factors, including the large number of skeletal dysplasias and their phenotypic variability with overlapping features, lack of precise molecular diagnosis for many disorders, lack of a systematic approach, the inability of ultrasonography (US) to provide an integrated view, and variability in the time at which findings manifest in some skeletal dysplasias. US of suspected skeletal dysplasia involves systematic imaging of the long bones, thorax, hands and feet, skull, spine, and pelvis. Assessment of the fetus with three-dimensional US has been shown to improve diagnostic accuracy, since additional phenotypic features not detectable at two-dimensional US may be identified. The radiologist plays a major role in making an accurate diagnosis; however, representatives of other disciplines, including clinicians, molecular biologists, and pathologists, can also provide important diagnostic information.