Hereditary Multiple Exostoses: Current Insights

Hereditary multiple exostoses with a giant osteochondroma degenerated into chondrosarcoma

We present a case of hereditary multiple exostoses with malignant transformation to chondrosarcoma in a woman complaining of enlargement and pain in the right thigh. Hereditary multiple exostoses is a rare genetic disorder characterized by multiple osteochondromas. Malignant transformation to chondrosarcoma of a pre-existing osteochondroma is a possible significant manifestation of this hereditary syndrome. Imaging modalities such as X-ray, Ultrasound, and computed tomography play a crucial role in the diagnosis and management of these patients, as described in this case.

A Rare Case of Hereditary Multiple Exostoses in a Woman

Hereditary multiple exostosis (HME) is a rare genetic disorder characterized by multiple bony spurs or lumps, commonly affecting the long bones. This case report exposes the clinical presentation, diagnosis, and management of HME in a 28-year-old female nurse, who initially presented with persistent bilateral knee pain. After extensive evaluation involving orthopaedic and oncology specialists, the diagnosis of HME was made. Despite the discovery of multiple exostoses, the patient reported improvement following a tailored physiotherapy regimen. This case study underscores the complexity and broad spectrum of symptoms associated with HME. It emphasizes the importance of a multidisciplinary approach in diagnosing and managing such conditions, which can lead to better patient outcomes and an improved quality of life. By shedding light on the role of physiotherapy in managing rare genetic disorders such as HME, this case report contributes to the growing body of literature exploring noninvasive treatment options for these diseases.

Popliteal pseudoaneurysm in a young patient with multiple hereditary exostosis

Multiple hereditary exostosis is an osteogenic disorder that causes outgrowths of cartilaginous bone tumors that are associated with adjacent neurovascular compressive injuries. We present the case of an adolescent male with multiple hereditary exostosis complicated by popliteal pseudoaneurysm formation who underwent excision of the osteochondroma and vein patch angioplasty repair of the artery. We highlight the rare association between this genetic disease and subsequent vascular complications and review the available literature of arterial complications of this disease.

Osteochondroma of the Mandibular Condyle: A Rare Case Presentation With Literature Review

Osteochondromas (OCs) are benign bone tumors characterized by their growth with a cartilage cap and typically occurring at the ends of long bones. Their occurrence in the head and neck region is infrequent, accounting for only around 1% of head and neck tumors. Notably, the mandibular coronoid process and the mandibular condyle are the primary sites where an OC is reported. Patients often exhibit facial asymmetry, limited mouth opening, and malocclusion. Possible treatment options depending on the condition include partial or total condylectomy, vertical ramus osteotomy, and supplementary orthognathic surgery. The recurrence rate of under 1%- 2% is reported after local resection.  In this case report, we present a unique case of an OC in a 27-year-old woman. It involved the mandibular condyle, resulting in a left-sided mouth deviation while opening and closing her mouth. The purpose of this article is to detail the clinical and radiographic features, histopathological aspects, and treatment strategies and differentiate potential diagnoses, for such OCs.

One-Bone Forearm Procedure for Severe Recalcitrant Forearm Deformities in Masada IIb Hereditary Multiple Exostoses

Introduction

Hereditary multiple exostoses (HME) Masada IIB has traditionally been treated by gradual ulnar lengthening with questionable efficacy in reducing the dislocated head. One-bone forearm (OBF) has been used as a reconstructive procedure in forearm deformities with very scarce literature for HME. The study aims to report short-term results of OBF as a definitive procedure for severe forearm deformities in Masada IIB patients with respect to clinical and radiological parameters.

Materials and Methods

Four patients with HME Masada IIb were included in this retrospective study. All patients complained of forearm and wrist deformity with an abnormal bony protrusion restricting elbow motion. Indications for OBF were ulnar shortening > 3 cm, dysplastic proximal radius with convex radial head and restricted prono-supination. All patients were examined pre-operatively and post-operatively clinically and radiographically using the Peterson's outcome score.

Results

The average age was 13 years (12-14 years). Pre-operative ulnar shortening, carpal slip percentage, and radial articular angle was 3.4 cm, 79.5%, and 47.5°, respectively. All radial heads were dislocated with convex articular surface restricting elbow extension and forearm prono-supination. At the latest follow-up, the mean elbow flexion was 110° with forearm in 10° supination. The mean carpal slip percentage, radial articular angle, and Peterson functional grade was 15%, 22.5°, and 8 points, respectively. The mean follow-up period was 30.25 months with no recurrence.

Conclusion

We recommend one bone forearm as a definitive procedure in HME Masada IIB patients with severe forearm deformities with ulnar shortening > 3 cm and dysplastic proximal radius with a dislocated radial head, for faster return to function.

Ollier Disease: A Case Report and Review of Treatment Options

Ollier disease is a rare skeletal dysplasia characterized by the formation of multiple enchondromas (enchondromatosis), typically in the long bones of the extremities. These tumors are benign but can become complicated by the development of pathologic fractures, limb deformity, and malignant transformation to chondrosarcoma. Ollier disease has a highly variable presentation and is associated with a range of presenting findings; however, the most common presentation is a pathologic fracture. Surgical options include curettage and grafting of the enchondromas and, when displaced, fracture reduction and fixation. Of note, these fractures will heal without surgery. Regardless, all patients must be routinely monitored with yearly radiographs in order to detect malignant transformation as early as possible.  In this report, we describe the case of an 11-year-old female who presented to her physician with pain and swelling of her right ring and small fingers after playing in a swimming pool with no obvious mechanism of trauma. A routine, plain radiographic evaluation of her hand revealed the presence of multiple enchondromatosis. We hope to use this case to highlight the surgical management options for young patients with Ollier disease and discuss circumstances in which surgical management may not be indicated.

Phenotypic and Molecular Spectrum of a Turkish Cohort with Hereditary Multiple Osteochondromas

OBJECTIVE

Hereditary multiple osteochondromas is an autosomal dominant disorder caused by heterozygous pathogenic variants in EXT1 or EXT2. We aimed to evaluate the clinical and molecular findings of a Turkish cohort with hereditary multiple osteochondroma.

MATERIALS AND METHODS

Thirty-two patients aged 1.3-49.6 years from 22 families were enrolled. Genetic analyses were made by EXT1 and/or EXT2 sequencing and chromosomal microarray analyses.

RESULTS

We found 17 intragenic pathogenic variants in EXT1 (13/17) and EXT2 (4/17), 12 of which are novel. Four probands had EXT1 deletions, including 2 patients with partial EXT1 microdeletions involving exons 2-11 and 5-11, and 2 patients with whole-gene deletions. In 21 variants, the frequency of truncating and missense variants was 76.1% and 23.8%, respectively. Two families had no detectable variants in EXT1 and EXT2. All patients had multiple osteochondromas at the long bones, mainly at the tibia, forearm, femur, and humerus. Bowing deformity of the forearms (9/32) and the lower extremities (2/32), and scoliosis (6/32) were observed. The clinical severity was not different between patients with EXT1 or EXT2 variants. One patient with an EXT2 variant and another with an EXT1 microdeletion had the most severe phenotype with class III disease. Four patients with no EXT1 or EXT2 variants had milder phenotypes. Intrafamilial variability in disease severity was not observed.

CONCLUSION

We report a hereditary multiple osteochondroma cohort with clinical and molecular data including 12 novel intragenic variants in EXT1 or EXT2, and 4 microdeletions involving EXT1. Taken together, our data expand the existing knowledge of the phenotype-genotype spectrum in hereditary multiple osteochondroma.

Chest wall osteochondroma resection with biologic acellular bovine dermal mesh reconstruction in pediatric hereditary multiple exostoses: A case report and review of literature

BACKGROUND

Hereditary multiple exostoses is a rare genetic disorder characterized by the growth of multiple osteochondromas affecting primarily long bones. Chest wall lesions may represent a challenge, particularly in pediatric patients. Pain is a common manifestation. However, life-threatening complications can result from direct involvement of adjacent structures. Surgical resection with appropriate reconstruction is often required.

CASE SUMMARY

A 5-year-old male who was diagnosed with hereditary multiple exostoses presented with significant pain from a large growing chest wall exostosis lesion. After appropriate preoperative investigations, he underwent surgical resection with reconstruction of his chest wall using a biologic bovine dermal matrix mesh.

CONCLUSION

Resection of chest wall lesions in children represents a challenge. Preoperative planning to determine the appropriate reconstruction strategy is essential.

Sacroiliac joint involvement in osteochondromatosis: identifying its prevalence and characteristics from cross-sectional imaging

PURPOSE

Apart from a few case reports, sacroiliac joint (SIJ) involvement in osteochondromatosis has not been studied. We aimed to determine the prevalence and characteristics of such involvement using cross-sectional imaging.

METHODS

In this retrospective study, three observers (one junior radiologist and two musculoskeletal radiologists) independently reviewed computed tomography (CT) or magnetic resonance imaging (MRI) of patients in our database who had osteochondromatosis (≥2 osteochondromas across the skeleton) for SIJ involvement. The final decision was reached by the consensus of the two musculoskeletal radiologists in a later joint session.

RESULTS

Of the 36 patients with osteochondromatosis in our database, 22 (61%) had cross-sectional imaging covering SIJs (14 females, 8 males; age range 7-66 years; mean age 23 years; 13 MRI, 9 CT). Of these, 16 (73%) had intra-articular osteochondromas. For identifying SIJ osteochondromas on cross-sectional imaging, interobserver agreement was substantial [κ = 0.67; 95% confidence interval (CI): 0.34, 1.00] between the musculoskeletal radiologists and moderate (κ = 0.59; 95% CI: 0.23, 0.94) between the junior radiologist and the final consensus decision of the two musculoskeletal radiologists. In the cohort with cross-sectional imaging, the anatomical variations of the accessory SIJ (n = 6, 27%) and iliosacral complex (n = 2, 9%) were identified in six different patients with (n = 2) and without (n = 4) sacroiliac osteochondromas.

CONCLUSION

Cross-sectional imaging shows frequent (73%) SIJ involvement in osteochondromatosis, which, although a rare disorder, nevertheless needs to be considered in the differential diagnosis of such SIJ anatomical variants as the accessory SIJ and iliosacral complex. Differentiating these variants from osteochondromas is challenging in patients with osteochondromatosis.

Osteochondroma of the Scapula: A Case Report and Literature Review

Osteochondromas are bone lesions composed of medullary and cartilaginous bone covered by a cap of hyaline cartilage. The presence of medullary and cortical bone with the continuity of the tumor is pathognomonic for osteochondroma and aid in establishing the diagnosis. We report a case of a two-year-old girl who presented to our clinic following her mother noticing a palpable, growing, and painful mass on her left scapula. There was no limitation in the range of motion. A clear-cut mass was seen on the dorsal aspect and palpated measuring around 2.5x3 cm. Surgical excision of the mass followed by histologic examination confirmed osteochondroma. Upon follow-up, the patient had no pain and had a full range of left shoulder motion without discomfort or pain. In conclusion, scapular exostoses are very rare and more so when they present dorsally. Symptomatic lesions can be managed effectively with surgical excision of exostosis.

Genetic analysis of seven pateints with Hereditary Multiple Osteochondromas (HMO)

BACKGROUND

HMO (Hereditary Multiple Osteochondroma), an uncommon autosomal dominant disorder, is characterized by the development of multiple osteochondromas, which are nonmalignant cartilage-capped bone tumors growing outwards from long bone metaphyses.

METHODS

The present work retrospectively analyzed seven children with HMO who were enrolled for routine clinical diagnosis and treatment, including X-ray examination. Subsequent genetic detection was carried out using whole exome sequencing (WES). In addition, this work applied Sanger sequencing to be the validation approach. Moreover, this work also examined amino acid (AA) evolutionary conservatism under the influence of certain missense variants.

RESULTS

The clinical indications of all seven patients and their family members were thoroughly indexed. WES identified diagnostic variants in the EXT1 or EXT2 gene in these patients. In these variants, four were reported for the first time, namely EXT1: c.1285-2A>T, EXT2: c.1139delT, EXT1: c.203G>A, and EXT1: c.1645_1673del. Familial validation revealed that three of the variants were hereditary, while the other four were de novo, which was consistent with the phenotype in each case.

CONCLUSION

Our results expanded HMO variation spectrum, and laid certain foundations for the precise counseling of those affected families.

The identification of a novel frameshift insertion mutation in the EXT1 gene in a Chinese family with hereditary multiple exostoses

To identify the pathogenic gene variation in a Chinese family with Hereditary Multiple Exostoses (HME). By examining blood‐sourced DNA and clinical manifestations of the proband and his family members, the whole exome sequencing (WES) and Sanger sequencing were used to detect possibly pathogenic mutations. A novel heterozygous mutation (c.325dup) was identified in exon 1 of the exostosin 1 (EXT1) gene from the proband and the affected family members. And we found this mutation was absent in all the unaffected family members. This c.325dup mutation is in the exon 1 domain of the EXT1 gene and the change of p.C109Lfs*80 cause the early termination of protein translation. The identification of the novel frameshift insertion mutation (c.325dup) expands the mutation spectrum of HME, which provides new evidence for HME diagnosis.

Suppression of heparan sulfation re-sensitizes YAP1-driven melanoma to MAPK pathway inhibitors

Accumulating evidence identifies non-genetic mechanisms substantially contributing to drug resistance in cancer patients. Preclinical and clinical data implicate the transcriptional co-activators YAP1 and its paralog TAZ in resistance to multiple targeted therapies, highlighting the strong need for therapeutic strategies overcoming YAP1/TAZ-mediated resistance across tumor entities. Here, we show particularly high YAP1/TAZ activity in MITF^low/AXL^high melanomas characterized by resistance to MAPK pathway inhibition and broad receptor tyrosine kinase activity. To uncover genetic dependencies of melanoma cells with high YAP1/TAZ activity, we used a genome-wide CRISPR/Cas9 functional screen and identified SLC35B2, the 3′-phosphoadenosine-5′-phosphosulfate transporter of the Golgi apparatus, as an essential gene for YAP1/TAZ-driven drug resistance. SLC35B2 expression correlates with tumor progression, and its loss decreases heparan sulfate expression, reduces receptor tyrosine kinase activity, and sensitizes resistant melanoma cells to BRAF inhibition in vitro and in vivo. Thus, targeting heparan sulfation via SLC35B2 represents a novel approach for breaking receptor tyrosine kinase-mediated resistance to MAPK pathway inhibitors.

Spatiotemporal diversity and regulation of glycosaminoglycans in cell homeostasis and human disease

Glycosaminoglycans (GAGs) are long, linear polysaccharides that are ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These complex carbohydrates play important roles in many cellular processes and have been implicated in many disease states, including cancer, inflammation, and genetic disorders. GAGs are among the most complex molecules in biology with enormous information content and extensive structural and functional heterogeneity. GAG biosynthesis is a nontemplate-driven process facilitated by a large group of biosynthetic enzymes that have been extensively characterized over the past few decades. Interestingly, the expression of the enzymes and the consequent structure and function of the polysaccharide chains can vary temporally and spatially during development and under certain pathophysiological conditions, suggesting their assembly is tightly regulated in cells. Due to their many key roles in cell homeostasis and disease, there is much interest in targeting the assembly and function of GAGs as a therapeutic approach. Recent advances in genomics and GAG analytical techniques have pushed the field and generated new perspectives on the regulation of mammalian glycosylation. This review highlights the spatiotemporal diversity of GAGs and the mechanisms guiding their assembly and function in human biology and disease.

Physiology and Pathophysiology of Heparan Sulfate in Animal Models: Its Biosynthesis and Degradation

Heparan sulfate (HS) is a type of glycosaminoglycan that plays a key role in a variety of biological functions in neurology, skeletal development, immunology, and tumor metastasis. Biosynthesis of HS is initiated by a link of xylose to Ser residue of HS proteoglycans, followed by the formation of a linker tetrasaccharide. Then, an extension reaction of HS disaccharide occurs through polymerization of many repetitive units consisting of iduronic acid and N-acetylglucosamine. Subsequently, several modification reactions take place to complete the maturation of HS. The sulfation positions of N-, 2-O-, 6-O-, and 3-O- are all mediated by specific enzymes that may have multiple isozymes. C5-epimerization is facilitated by the epimerase enzyme that converts glucuronic acid to iduronic acid. Once these enzymatic reactions have been completed, the desulfation reaction further modifies HS. Apart from HS biosynthesis, the degradation of HS is largely mediated by the lysosome, an intracellular organelle with acidic pH. Mucopolysaccharidosis is a genetic disorder characterized by an accumulation of glycosaminoglycans in the body associated with neuronal, skeletal, and visceral disorders. Genetically modified animal models have significantly contributed to the understanding of the in vivo role of these enzymes. Their role and potential link to diseases are also discussed.

Genetic and functional analyses detect an EXT1 splicing pathogenic variant in a Chinese hereditary multiple exostosis (HME) family

Background

Hereditary multiple exostosis (HME) is an autosomal dominant skeletal disorder characterized by the development of multiple cartilage‐covered tumors on the external surfaces of bones (osteochondromas). Most of HME cases result from heterozygous loss‐of‐function mutations in EXT1 or EXT2 gene.

Methods

Clinical examination was performed to diagnose the patients: Whole exome sequencing (WES) was used to identify pathogenic mutations in the proband, which is confirmed by Sanger sequencing and co‐segregation analysis: qRT‐PCR was performed to identify the mRNA expression level of EXT1 in patient peripheral blood samples: minigene splicing assay was performed to mimic the splicing process of EXT1 variants in vitro.

Results

We evaluated the pathogenicity of EXT1 c.1056 + 1G > T in a Chinese family with HME. The clinical, phenotypic, and genetic characterization of patients in this family were described. The variant was detected by whole‐exome sequencing (WES) and confirmed by Sanger sequencing. Sequencing of the RT‐PCR products from the patient's blood sample identified a large deletion (94 nucleotides), which is the whole exome 2 of the EXT1 cDNA. Splicing assay indicated that the mutated minigene produced alternatively spliced transcripts, which cause a frameshift resulting in an early termination of protein expression.

Conclusions

Our study establishes the pathogenesis of the splicing mutation EXT1 c.1056 + 1G > T to HME and provides scientific foundation for accurate diagnosis and precise medical intervention for HME.

Hereditary Multiple Exostoses-A Review of the Molecular Background, Diagnostics, and Potential Therapeutic Strategies

Hereditary multiple exostoses (HMEs) syndrome, also known as multiple osteochondromas, represents a rare and severe human skeletal disorder. The disease is characterized by multiple benign cartilage-capped bony outgrowths, termed exostoses or osteochondromas, that locate most commonly in the juxta-epiphyseal portions of long bones. Affected individuals usually complain of persistent pain caused by the pressure on neighboring tissues, disturbance of blood circulation, or rarely by spinal cord compression. However, the most severe complication of this condition is malignant transformation into chondrosarcoma, occurring in up to 3.9% of HMEs patients. The disease results mainly from heterozygous loss-of-function alterations in the EXT1 or EXT2 genes, encoding Golgi-associated glycosyltransferases, responsible for heparan sulfate biosynthesis. Some of the patients with HMEs do not carry pathogenic variants in those genes, hence the presence of somatic mutations, deep intronic variants, or another genes/loci is suggested. This review presents the systematic analysis of current cellular and molecular concepts of HMEs along with clinical characteristics, clinical and molecular diagnostic methods, differential diagnosis, and potential treatment options.

A Case Report of Trevor's Disease in a Pediatric Patient with Hereditary Multiple Exostoses Disease

Introduction

Hereditary multiple exostoses (HME) disease is hallmarked by cartilaginous osteochondromas secondary to an autosomal dominant mutation within the exostosin gene family. These outgrowths predominantly occur around the long bone physis. An associated disease is dysplasia epiphysealis hemimelica also known as Trevor's disease. Trevor's disease is hallmarked by intra-articular osteochondromas. While the two diseases are similar, they are not genetically related and often have differing patient presentations.

Case Report

We report on a case of a 7-year-old female with a familial history significant for HME that presented with an isolated chief complaint of elbow extension block secondary to osteochondromas found both intra-articular and at the olecranon fossa. We present what could be one of the first cases of coexisting HME and Trevor's disease of the upper extremity.

Conclusion

Our patient's unique presentation of an intra-articular osteochondroma speculated to be a result of Trevor's disease, in the presence of an established HME diagnosis. Management for this patient did not deviate heavily from the established approach for HME which entails conservative observation until symptomatic. Due to the substantial loss of range of motion (ROM), surgical intervention took place in the form of exostoses removal and necessary reconstruction of the fossa. The patient's ROM subsequently was restored to near normal.

Popliteal artery pseudoaneurysm caused by non-penetrating trauma in a patient with hereditary multiple osteochondromatosis

Hereditary multiple osteochondromatosis is a genetic condition characterized by the appearance of numerous osteochondromas, which can cause pseudoaneurysms in rare cases. The following article describes a 15-year-old patient with a history of current massages as part of his gym routine, who arrived at the emergency department with 4 days of pain, and ecchymosis in the right popliteal region. Therefore, duplex ultrasonography and arteriography were performed, confirming the diagnosis of popliteal pseudoaneurysm, which was subsequently treated by open surgery, providing a satisfactory outcome.

Giant ulcerative benign osteochondroma of shoulder

Osteochondromas in hereditary multiple exostosis have increased risk of malignant transformation as compared with solitary osteochondromas. We present a case of a 54-year-old man who presented to us with complaints of swollen mass of the left shoulder with an ulcerative lesion. Radiograph showed a sessile growth from the proximal humerus and scapula. MRI revealed a sessile osteochondroma measuring about 11×10.1×8.0 cm. The malignant nature of the disease was anticipated due to increased cap thickness and non-healing ulcer, however, biopsy showed a benign lesion without any sarcomatous change. The patient was successfully treated with extra-periosteal excision and was recurrence-free at 24 months follow-up. This case illustrates an extra-articular giant osteochondroma of the proximal humerus, with possible signs of a malignant lesion but diagnosed benign on biopsy. We conclude that a biopsy should always preclude definitive management as this can change the overall mortality and morbidity of the patient.

Diaphyseal Aclasis With Pes Anserinus Syndrome

We describe the case of a 20-year-old man who presented with a bony swelling over the medial proximal tibia that caused pain along the pes anserinus tendons, and a history of multiple asymptomatic bony swellings. Wide extraperiosteal resection of the swelling relieved the symptoms with a good outcome within a year. This report describes the pictorial pathoanatomy of a relatively rare association of pes anserinus syndrome caused by osteochondroma in an adult patient. Proximal tibial osteochondromas can also present as pes anserinus syndrome in adult patients with diaphyseal aclasis. Large swellings require wide excision to relieve the stretching pain of pes tendons.

Osteochondromas: An Updated Review of Epidemiology, Pathogenesis, Clinical Presentation, Radiological Features and Treatment Options

Osteochondroma, the most common benign bone tumor, is a projection on the external surface of the bone, which can be sessile or pedunculated. 85% of osteochondromas present as solitary lesions, while 15% occur in the context of hereditary multiple exostoses (HME), a genetic disorder that is inherited in an autosomal dominant manner. Although often asymptomatic, symptoms may eventuate from compression of adjacent vessels or nerves, fractures, osseous deformities, bursa formation, or malignant transformation. Cartilage cap thickness >2 cm in adults or >3 cm in children as well as new onset of pain or growth, or rapid growth of the lesion, especially after the closure of the growth plate, might reflect cancerous transformation. Surgical resection is indicated for symptomatic lesions, complications, cosmetic reasons or malignant transformation. Excision of the tumor with free margin is the treatment of choice. Local recurrence is less than 2% if complete resection is achieved.

Some Reactive Lesions of Bone Are Probably Neoplasms: A Review

CONTEXT.—

A number of fibro-osseous and osteocartilaginous lesions, especially common in the small bones of hand and feet, pose a diagnostic challenge and have historically been thought to be reactive lesions. However, modern molecular techniques when supplementing clinical, radiographic, and histologic evaluation suggest they may, in fact, be neoplasms.

OBJECTIVE.—

To review the clinical presentation and histopathologic, molecular, and radiologic features of selective bone lesions, focusing most specifically on subungual exostosis, florid reactive periostitis, and bizarre periosteal osteochondromatous proliferation.

DATA SOURCES.—

Literature review and personal experience are the source of this review.

CONCLUSIONS.—

Some lesions previously thought to be reactive are locally aggressive and demonstrate reproducible molecular abnormalities, and thus may be neoplasms. Although most common in the bones of the fingers and toes, these lesions also occur in long and other bones. The clinical presentations, radiologic appearances, and histopathologic features often overlap, making the diagnosis challenging, and these lesions may require molecular evaluation to maximize accurate prognostication.

A Family with Hereditary Multiple Exostoses

Hereditary multiple exostoses is a rare autosomal dominant genetic disorder characterized by multiple exostoses (osteochondromas), mostly diagnosed in childhood. It may manifest with a wide spectrum from asymptomatic to skeletal deformities or neurovascular complications. Pain and/or swelling are often the first symptoms for patients to consult a doctor. Although no medical treatment is currently available, lesions can be removed with surgical excision in case of aesthetic anxiety or complications such as deformities or rarely, malign transformation. In this article, three individuals from the same family with hereditary multiple exostoses are described who were evaluated within the core competencies of family medicine. Keywords: exostoses, multiple hereditary, osteochondroma, scoliosis

Mechanisms of Primary Membranous Nephropathy

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogenous outcomes with approximately 30% of cases progressing to end-stage renal disease. The clinical management of MN has steadily advanced owing to the identification of autoantibodies to the phospholipase A2 receptor (PLA2R) in 2009 and thrombospondin domain-containing 7A (THSD7A) in 2014 on the podocyte surface. Approximately 50–80% and 3–5% of primary MN (PMN) cases are associated with either anti-PLA2R or anti-THSD7A antibodies, respectively. The presence of these autoantibodies is used for MN diagnosis; antibody levels correlate with disease severity and possess significant biomarker values in monitoring disease progression and treatment response. Importantly, both autoantibodies are causative to MN. Additionally, evidence is emerging that NELL-1 is associated with 5–10% of PMN cases that are PLA2R- and THSD7A-negative, which moves us one step closer to mapping out the full spectrum of PMN antigens. Recent developments suggest exostosin 1 (EXT1), EXT2, NELL-1, and contactin 1 (CNTN1) are associated with MN. Genetic factors and other mechanisms are in place to regulate these factors and may contribute to MN pathogenesis. This review will discuss recent developments over the past 5 years.

An unusual example of hereditary multiple exostoses: a case report and review of the literature

Background

Hereditary multiple exostoses (HME) is a rare skeletal disorder characterised by a widespread.

distribution of osteochondromas originating from the metaphyses of long bones.

Case presentation

This case study examines a 55-year-old male cadaver bequeathed to the University of Liverpool who suffered from HME, thus providing an exceptionally rare opportunity to examine the anatomical changes associated with this condition.

Conclusions

Findings from imaging and dissection indicated that this was a severe case of HME in terms of the quantity and distribution of the osteochondromas and the number of synostoses present. In addition, the existence of enchondromas and the appearance of gaps within the trabeculae of affected bones make this a remarkable case. This study provides a comprehensive overview of the morbidity of the disease as well as adding to the growing evidence that diseases concerning benign cartilaginous tumours may be part of a spectrum rather than distinct entities.

Hereditary multiple osteochondromas in Jordanian patients: Mutational and immunohistochemical analysis of EXT1 and EXT2 genes

The aim of the present study was to investigate the molecular characteristics of hereditary multiple osteochondromas (HMO) in a subset of Jordanian patients with a focus on the genetic variants of exostosin (EXT1)/(EXT2) and their protein expression. Patients with HMO and their family members were included. Recorded clinical characteristics included age, sex, tumors number and location, joint deformities and associated functional limitations. Mutational analysis of EXT1 and EXT2 exonic regions was performed. Immunohistochemical staining for EXT1 and EXT2 was performed manually using two different commercially available rabbit anti-human EXT1 and EXT2 antibodies. A total of 16 patients with HMO from nine unrelated families were included, with a mean age of 13.9 years. A total of 75% (12/16) of the patients were male and (69%) (11/16) had a mild disease (class I). EXT mutation analysis revealed only EXT1 gene mutations in 13 patients. Seven variants were detected, among which three were novel: c.1019G>A, p. (Arg340His), c.962+1G>A and c.1469del, p. (Leu490Argfs*9). Of the 16 patients, 3 did not harbor any mutations for either EXT1 or EXT2. Immunohistochemical examination revealed decreased expression of EXT1 protein in all patients with EXT1 mutation. Surprisingly, EXT2 protein was not detected in these patients, although none had EXT2 mutations. The majority of Jordanian patients with HMO, who may represent an ethnic group that is infrequently investigated, were males and had a mild clinical disease course; whereas most patients with EXT1 gene mutations were not necessarily associated with a severe clinical disease course. The role of EXT2 gene remains a subject of debate, since patients with EXT1 mutations alone did not express the non-mutated EXT2 gene.

EXT1 and EXT2 Variants in 22 Chinese Families With Multiple Osteochondromas: Seven New Variants and Potentiation of Preimplantation Genetic Testing and Prenatal Diagnosis

Multiple osteochondromas (MO), the most common type of benign bone tumor, is an autosomal dominant skeletal disorder characterized by multiple cartilage-capped bony protuberances. In most cases, EXT1 and EXT2, which encode glycosyltransferases involved in the biosynthesis of heparan sulfate, are the genes responsible. Here we describe the clinical, phenotypic and genetic characterization of MO in 22 unrelated Chinese families involving a total of 60 patients. Variant detection was performed by means of a battery of different techniques including Sanger sequencing and whole-exome sequencing (WES). The pathogenicity of the missense and splicing variants was explored by means of in silico prediction algorithms. Sixteen unique pathogenic variants, including 10 in the EXT1 gene and 6 in the EXT2 gene, were identified in 18 (82%) of the 22 families. Fourteen (88%) of the 16 variants were predicted to give rise to truncated proteins whereas the remaining two were missense. Seven variants were newly described here, further expanding the spectrum of MO-causing variants in the EXT1 and EXT2 genes. More importantly, the identification of causative variants allowed us to provide genetic counseling to 8 MO patients in terms either of preimplantation genetic testing (PGT) or prenatal diagnosis, thereby preventing the reoccurrence of MO in the corresponding families. This study is the first to report the successful implementation of PGT in MO families and describes the largest number of subjects undergoing prenatal diagnosis to date.

Novel deletion and 2397 G>T mutations of the EXT1 gene identified in two Chinese pedigrees with hereditary multiple exostoses using exon sequencing

BACKGROUND

Hereditary multiple exostoses (HME), a rare genetic pediatric disorder, has a peculiar pathogenic mechanism. The results of previous studies have shown that HME is associated with mutations of the EXT1 and EXT2 genes at a molecular genetics level. In our study, two families who received therapy in the Department of Orthopedics of Shanghai Children's Hospital between June, 2017 and November, 2018 were recruited, and a mutational analysis of the EXT1 genes was conducted to further elucidating the relationship between HME and EXT1.

METHODS

Venous blood samples were collected from individuals with HME and their families. Exon sequencing and RT-PCR were performed to comprehensively analyze 11 exons of the EXT1 gene.

RESULTS

The deletion of exon 7 and the 2397 G>T mutation in exon 7 caused deletion mutation and nonsense mutation only in the HME patients. The mutations in exon 7 were tested and verified by Sanger sequencing. RT-PCR showed that the mRNA expression of EXT1 was significantly decreased in the mutation samples compared with the normal samples, which exerted a great influence on the function of EXT1.

CONCLUSIONS

This study identified new mutation sites for the pathogenesis of HME and further clarified the relationship between HME and EXT1.

Segmental Fibulectomy to Excise the Adherent Distal Tibia Osteochondroma in a Case of Hereditary Multiple Exostosis - A Rare Case Report

INTRODUCTION

Hereditary multiple exostosis (HME) is an autosomal dominant disorder affecting the skeletal system, which is characterized by multiple osteochondromas in bones arising from osteochondral ossification and leading to skeletal deformities, short stature, soft tissue, and neurovascular compressive symptoms.

CASE REPORT

A 10-year-old female a case of HME presented with painless multiple swelling around knees, wrist, and painful varus deformity in the lower third of the right leg. The large exostosis of the right distal tibia was symptomatic and indenting the fibula which required excision along with the segment of the fibula of about 2.5 cm above the syndesmosis adjacent to the exostosis as the mass was adherent to the fibula.

CONCLUSION

Although distal tibia osteochondromas are rare, they can lead to deformity of the ankle and loss of function if not managed early and properly. Hence, early detection, proper planning, and management of periarticular distal tibia osteochondromas are essential to prevent the development or progression of the deformity. Segmental fibulectomy is required to remove the adherent osteochondromas completely and to prevent the recurrence and secondary surgical procedures. It is very essential to follow up the patient till the skeletal maturity to identify the delayed presentation and late progression of the ankle deformities.

Identification of Novel EXT Mutations in Patients with Hereditary Multiple Exostoses Using Whole-Exome Sequencing

Objective

To find novel potential gene mutations other than EXT1 and EXT2 mutations, to expand the mutational spectrum of EXT and to explore the correlation between clinical outcome and genotype in patients with hereditary multiple exostoses (HME).

Methods

The study recruited seven families diagnosed with multiple osteochondromas (MO). Family histories and clinical information were collected in detail through comprehensive physical and image examination. Patients with deformities and functional limitations were classified as “severe” and the remaining without functional limitations were classified as “mild,” in accordance with previous study. Whole‐exome sequencing (WES) was performed on a total of 13 affected individuals, 1 available unaffected relative, and 10 healthy unrelated individuals. Sanger sequencing was used to validate the screened mutations. Finally, the structural change in protein caused by pathogenic mutations was analyzed using information from the relevant database online and we attempted to correlate clinical phenotype with genotype in patients with HME.

Results

Other than EXT1 and EXT2, no novel potential gene mutations were found through WES. We identified nine heterozygous mutations in EXT1 or EXT2. Of these mutations, four have not been reported previously. These are c.996delT in exon 2 of EXT1 (family 1), c.544C > T in exon 3 of EXT2 (family 2), c.1171C > T in exon 7 of EXT2 (family 5), and c.823_–824delAA in exon 5 of EXT1 (family 7). The other five mutations have already been reported in previous works. It was surprising that we found two mutation sites, in exon 2 and exon 5, respectively, of EXT1 in 1 patient diagnosed with MO, when his father had two mutation sites, in exon 6 and exon 5, respectively, of EXT1 and EXT2 (family 4). In addition, 1 patient showed degeneration, while his father only exhibited slight symptoms (family 7). In our study, among 51 affected patients in seven families, the sex ratio (male vs female) was 58.9% (n = 30) vs 41.2% (n = 21). Male patients seemed to show more severe symptoms compared to females, but because the sample was small, we did not obtain statistically significance results.

Conclusion

Whole‐exome sequencing to screen pathogenic gene mutations was applied successfully. Although no third‐gene mutation associated with HME was found, a total of nine mutations across EXT1 and EXT2 were identified, four of which are novel. Our results expand the mutational spectrum of EXT and can be used in genetic counseling and prenatal diagnosis for patients with MO.