Hereditary Multiple Exostoses: New Insights into Pathogenesis, Clinical Complications, and Potential Treatments

Fluoride exposure and prevalence of osteochondroma in drinking water Endemic fluorosis areas of Heilongjiang Province, China: a cross-sectional study

To investigate the relationship between fluoride exposure and Osteochondroma (OC) prevalence, a cross-sectional study was conducted in drinking water endemic fluorosis areas of Heilongjiang Province, China. Our study first reported that the prevalence of OC was 2.3% in drinking water endemic fluorosis areas of Heilongjiang Province, China, and no difference in gender. Logistic regression analysis found that compared to 1st quartile participants, the prevalence of OC was 73% lower in the 2nd quartile participants of WF (Water fluoride), and 3.4 times higher among the 2nd quartile UF (Urinary fluoride) participants. Our study suggests that 0.259-0.420 mg/L of WF may be considered an appropriate level for reducing OC prevalence, while UF (≥0.750 mg/L) could slightly increase the prevalence of OC. In summary, the link between fluoride and OC prevalence is complicated and needs to be further investigated in a cohort population.

Lower extremity deformity and its risk factors in patients with solitary osteochondromas

BACKGROUND

This study aimed to demonstrate the occurrence of lower extremity deformities and their risk factors in patients with solitary osteochondromas.

METHODS

We retrospectively reviewed consecutive patients with solitary osteochondromas around the knee. The laterality (left or right), involved bone (femur or tibia), tumor type (pedunculated or sessile), and direction (medial or lateral) were examined. The whole limb length (WLL), mechanical lateral distal femoral angle (mLDFA), and medial proximal tibial angle (MPTA) were measured using teleroentgenogram. Lower limb deformity was defined as a difference of more than 5° in mLDFA or MPTA in both lower extremities or a difference in WLL of more than 1 cm. Patients were divided into two groups, with deformity and without deformity.

RESULTS

Lower extremity deformities were observed in 8 of 83 patients. Significant difference in the type of osteochondroma (p = 0.004) between the groups was observed. Differences in sex, age, laterality, involved bone, direction, and distance from the physis to the osteochondroma between groups were not statistically significant. The sessile type of osteochondroma was a risk factor for lower limb deformity with an odds ratio of 24.0 according to Firth's logistic regression analysis.

CONCLUSION

In our cohort with solitary osteochondroma, lower limb deformities were observed in 8 (9.6%) out of the 83 patients and these were significantly associated with sessile-type tumors. Therefore, patients with sessile-type solitary osteochondroma around the knee require careful surveillance of lower limb alignment with whole leg teleroentgenogram.

Surgical Approach and Considerations for Compressive Thoracic Intraspinal Osteochondroma in Familial Hereditary Multiple Exostosis

INTRODUCTION

Hereditary multiple exostosis or hereditary multiple osteochondromas is a very rare clinical condition. Usually, these lesions tend to occur in the pediatric population, remaining silent until adulthood. Moreover, current studies show a small prevalence in the male population. The osteochondromas usually occur at sites with great bone activity and turnover, such as the diaphysis or metaphyseal plates (especially in children) of long bones. Their appearance in short bones (such as vertebrae) is very rare.

CASE PRESENTATION

We present a case of familial HME in a 53-year-old female patient with a very uncommon clinical description of the disease. The patient presented at our hospital with Frankel D-type paraparesis, with multiple osteochondromas (located at the right humerus, bilateral femurs, right tibia, and hip joints, besides the numerous ones over the spinal column) and urinary incontinence. She was suffering from bilateral coxarthrosis and gonarthrosis, which limited severely the range of her movements. An early menopause status was brought into consideration by the patient, being installed circa 15 years before, at 38 years old. She was currently in treatment with bisphosphonates for her concomitant osteoporosis.

CONCLUSIONS

Despite the relatively rare nature of the disease, it may be an important concern for the patient's quality of life. Intraspinal processes may trigger paraparesis or other neurological statuses, which may require a surgical treatment. The nature of the lesions is usually benign and do not require further radio- or chemotherapy.

Pedunculated Osteochondroma Presenting as Verruca Vulgaris: A Diagnosis Requiring a High Index of Suspicion: Case Report

Introduction

Osteochondromas are the most common benign tumors of the bone and can be sessile or pedunculated. Although osteochondromas are typically seen in the long bones, they are rarely seen in the small bones of the hand or foot. Verruca vulgaris, also known as the common wart, is one of the most common skin conditions presenting to physicians and must be distinguished either clinically or histologically from other hyperkeratotic conditions, including bone conditions such as bone tumors that can place pressure on the skin and cause callus formation that can mimic a wart or create skin deformity. A high index of suspicion for underlying bone mass or tumor should be entertained when evaluating patients for skin conditions, particularly of the hand or foot, with failure to improve with treatment.

Case Report

This case report presents a 20-year-old male with a pedunculated osteochondroma of the left fourth distal phalanx with hyperkeratotic skin overlying the mass at the end of the toe. He was initially treated by a family doctor and podiatrist for verruca vulgaris for over 5 years with two treatments of liquid nitrogen cryotherapy and surgical excision of the mass when the treating podiatrist encountered bone and recommended radiographs. The family requested follow-up with our practice several days later after they were told the patient had a bone tumor. The patient requested surgical excision of the osteochondroma secondary to pain with activities and difficulties with his vocation as a pilot.

Conclusion

All physicians must be mindful of an underlying bone tumor or mass in patients presenting with skin changes, particularly about the foot or hand. Knowledge that an underlying bone tumor can present as a verruca vulgaris may prevent a delay in diagnosis or unnecessary treatment when evaluating and treating a patient with a skin lesion. Fortunately, our case was a benign osteochondroma; a malignant tumor with a delay in diagnosis could lead to loss of limb or life.

Secondary peripheral chondrosarcoma in multiple osteochondromas: a retrospective single-institution case series

BACKGROUND

Multiple osteochondromas is genetic disorder characterized by the formation of multiple benign cartilage-capped bone tumors, named osteochondromas, during skeletal development. The most feared complication is the secondary peripheral chondrosarcoma, a malignant cartilaginous neoplasm that arises from the chondroid cap of pre-existent osteochondromas. We conducted a retrospective cohort study on patients diagnosed and followed up from 1960 to 2019 to describe the clinical and pathological features of individuals affected by peripheral chondrosarcoma in multiple osteochondromas, to evaluate follow up information and individual outcome and to compare the results with literature. Data, including age, gender, site, histological grade, cartilage cap thickness, surgical treatments, surgical margins, genotype mutational status as well as treatment details were captured from the hospital electronic health records and from Registry of Multiple Osteochondromas. In addition, a complete histological review of all hematoxylin and eosin (H&E)-stained sections has been performed by expert pathologists.

RESULTS

One hundred five of the screened cases were included in the present study. The age at diagnosis of SPC ranges from 13 to 63, with median age at diagnosis of 34 years. The site most frequently affected by malignant degeneration was the pelvis (46 patients, 44%) with higher incidence in male patients (32 males vs.14 females). The second one was lower limbs (including femur, fibula, or tibia), identified in 35 patients. Histological information - available for 103 patients - showed: 59 patients with grade 1; 40 patients had a grade 2 and 4 patients had a grade 3. The most common surgical treatment was the complete resection, followed by debulking, amputation and partial resection. Most of cases did not have recurrence of the disease. Outcome in disease-free survival highlights that a worse course of the disease was associated with histological grade 2 or 3, and partial resection surgery. In most of analyzed cases (94%) a pathogenic variant was identified.

CONCLUSIONS

In conclusion, the present study gives an overview of the secondary peripheral chondrosarcomas, confirming that this disease represents an impacting complication for multiple osteochondromas patients and suggests that malignant transformation can occur also in younger patient, in a not irrelevant number of cases.

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.

Galectin-14 promotes hepatocellular carcinoma tumor growth via enhancing heparan sulfate proteoglycan modification

Hepatocellular carcinoma (HCC) is a highly heterogeneous malignancy and lacks effective treatment. Bulk-sequencing of different gene transcripts by comparing HCC tissues and adjacent normal tissues provides some clues for investigating the mechanisms or identifying potential targets for tumor progression. However, genes that are exclusively expressed in a subpopulation of HCC may not be enriched or detected through such a screening. In the current study, we performed a single cell-clone-based screening and identified galectin-14 as an essential molecule in the regulation of tumor growth. The aberrant expression of galectin-14 was significantly associated with a poor overall survival of liver cancer patients with database analysis. Knocking down galectin-14 inhibited the proliferation of tumor growth, whereas overexpressing galectin-14 promoted tumor growth in vivo. Non-targeted metabolomics analysis indicated that knocking down galectin-14 decreased glycometabolism; specifically that glycoside synthesis was significantly changed. Further study found that galectin-14 promoted the expression of cell surface heparan sulfate proteoglycans (HSPGs) that functioned as co-receptors, thereby increasing the responsiveness of HCC cells to growth factors, such as epidermal growth factor and transforming growth factor-alpha. In conclusion, the current study identifies a novel HCC-specific molecule galectin-14, which increases the expression of cell surface HSPGs and the uptake of growth factors to promote HCC cell proliferation.

Modified ulnar lengthening for correction of the Masada type 2 forearm deformity in hereditary multiple exostosis

Few articles have reported on the treatment of Masada type 2 forearm deformities in hereditary multiple exostosis, possibly because of the high redislocation rate and other complications. This study precisely declares the use of modified ulnar lengthening by an Ilizarov external fixation with tumour excision for the treatment of Masada type 2 forearm deformities. 20 children with Masada type 2 forearm deformities were admitted for surgical treatment at our hospital from February 2014 to February 2021. There were 13 girls and 7 boys, ranging in age from 3.5 to 15 years (mean: 9 years) at the time of operation. We removed the prominent osteochondromas of the distal ulna and the proximal radius, positioned a classic Ilizarov external fixator on the forearm and then performed ulnar transverse one-third proximal diaphyseal subperiosteal osteotomy. We adopted modified ulnar lengthening postoperatively. The effects of surgical correction of deformity and functional improvement of the limb were assessed via regular follow-up and X-ray. The patients were followed up for 36 months, and the ulna was lengthened 26.99 mm on average; all radial heads remained relocated. The radiographic evaluations, including relative ulnar shortening, radial articular angle, and carpal slip, were improved. The functions of the elbow and forearm were all improved after surgery. Modified ulnar lengthening by an Ilizarov external fixation with tumour excision for the treatment of Masada type 2 forearm deformities in hereditary multiple exostoses has been proven to be an effective and reliable technique in the early stage.

Advanced colon cancer coexisting with multiple Osteochondromatosis in a child; coincidence or causality? - A case report

INTRODUCTION AND IMPORTANCE

Childhood colorectal cancers are extremely rare and so is Osteochondromatosis. Both diseases do not have epidemiological records in African countries. The aim of this report is to present a rare coexistence of CRC and multiple enchondromas in a child.

PRESENTATION OF CASE

A case of a 12-year-old boy who presented with a large bowel obstruction secondary to an advanced tumor of the descending colon. He was also diagnosed with multiple osteochondromas affecting legs, arms, ribs, scapula, clavicle and pelvis. No positive family history was recorded. An urgent left hemicolectomy and diverting transverse colostomy was done. The colon can as stage IIIB and the patient received adjuvant chemotherapy. After 8 months of follow up, the colostomy was successfully reversed without any endoscopic signs of tumor growth or distant metastasis.

CLINICAL DISCUSSION

Colorectal cancer in childhood is rare. It may present with aggressive histological subtypes in children as compared to adults. There is little to no reports on the coexistence of colorectal cancer and multiple Osteochondromatosis. Microsatellite instability in DNA tumor is common in Colon Cancer and variety of mutations of EXT-1 and EXT-2 genes goes with Enchondromatosis.

CONCLUSION

The coexistence of two rare conditions is the remarkable issue in this case report. There are no prior reports in literature. Further genomic sequencing maybe required to better understand this coexistence.

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.

Hereditary multiple exostoses caused by a chromosomal inversion removing part of EXT1 gene

BACKGROUND

Hereditary multiple exostoses (HME) is an autosomal dominant skeletal disorder characterized by the development of multiple, circumscript and usually symmetric bony protuberances called osteochondromas. Most HME are caused by EXT1 and EXT2 loss of function mutations. Most pathogenic mutations are nonsense followed by missense mutations and deletions.

CASE PRESENTATION

Here we report on a patient with a rare and complex genotype resulting in a typical HME phenotype. Initial point mutation screening in EXT1 and EXT2 genes by Sanger sequencing did not reveal any pathogenic variants. The patient along with the healthy parents was subsequently referred for karyotype and array-Comparative Genomic Hybridization (CGH) analyses. Chromosomal analysis revealed two independent de novo apparently balanced rearrangements: a balanced translocation between the long arms of chromosomes 2 and 3 at breakpoints 2q22 and 3q13.2 and a pericentric inversion with breakpoints at 8p23.1q24.1. Both breakpoints were confirmed by Fluorescence In Situ Hybridization (FISH). Subsequently, array-CGH revealed a novel heterozygous deletion within the EXT1 gene at one of the inversion breakpoints, rendering the inversion unbalanced. The mode of inheritance, as well as the size of the deletion were further investigated by Quantitative Real-time PCR (qPCR), defining the deletion as de novo and of 3.1 kb in size, removing exon 10 of EXT1. The inversion in combination with the 8p23.1 deletion most likely abolishes the transcription of EXT1 downstream of exon 10 hence resulting in a truncated protein.

CONCLUSIONS

The identification of a rare and novel genetic cause of HME, highlights the importance of additional comprehensive investigation of patients with typical clinical manifestations, even when EXT1 and EXT2 mutation analysis is negative.

Evaluation of T helper17 as skeletal homeostasis factor in peripheral blood mononuclear cells and T helper cells of end-stage renal disease cases with impaired parathyroid hormone

BACKGROUND

Chronic renal failure is mainly connected with high and low parathyroid hormone (PTH) levels and immunological impairments. The present study aimed to evaluate T helper 17 (Th17) cells as a crucial modulator of the immune system and skeletal homeostasis in hemodialysis patients with impaired intact PTH (iPTH).

METHODS

In this research, blood samples were taken from ESRD patients with high (> 300 pg/mL), normal (150-300 pg/mL), and low (< 150 pg/mL) serum intact parathyroid hormone (iPTH( levels (n = 30 in each group). The frequency of Th17 (CD4⁺ IL17⁺) cells was evaluated by flow cytometry in each group. The expression levels of Th17 cell-related master transcription factors, cytokines in peripheral blood mononuclear cells (PBMC), and Th cells, and the level of the mentioned cytokines were determined in the supernatant of PBMCs.

RESULTS

The number of Th17 cells remarkably increased in subjects with high iPTH against low and normal iPTH. Also, RORɣt and STAT3 levels were significantly higher in high iPTH ESRD patients than in other groups in the expression of mRNA and protein levels. These findings are confirmed by evaluating the IL-17 and IL-23 in the supernatant of cultured PBMCs and isolated Th cells.

CONCLUSION

Our findings indicated that increased serum PTH levels in hemodialysis cases may be involved in increasing the differentiation of CD4 + cells to Th17 cells in PBMC.

Venous malformation may be a feature of EXT1-related hereditary multiple exostoses: A report of two unrelated probands

Hereditary multiple exostoses (HME), also known as hereditary multiple osteochondroma (HMO), is an autosomal dominant disorder caused by pathogenic variants in exostosin-1 or -2 (EXT1 or EXT2). It is characterized by the formation of multiple benign growing osteochondromas (exostoses) that most commonly affect the long bones; however, it may also occur throughout the body. Although many of these lesions are clinically asymptomatic, some can lead to chronic pain and skeletal deformities and interfere with adjacent neurovascular structures. Here, we report two unrelated probands that presented with a clinical and molecular diagnosis of HME with venous malformation, a clinical feature not previously reported in individuals with HME.

Genetic variants of cancer‑associated genes analyzed using next‑generation sequencing in small sporadic vestibular schwannomas

Vestibular schwannoma (VS) is the most common tumor of the cerebellopontine angle. Despite the increasing diagnosis of sporadic VS over the past decade, the use of traditional microsurgeries to treat VS has decreased. This is likely a result of the adoption of serial imaging as the most common initial evaluation and treatment strategy, especially for small-sized VS. However, the pathobiology of VSs remains unclear, and elucidating the genetic information of tumor tissue may reveal novel insights. The present study performed a comprehensive genomic analysis of all exons in the key tumor suppressor and oncogenes from 10 small (<15 mm) sporadic VS samples. The evaluations identified NF2, SYNE1, IRS2, APC, CIC, SDHC, BRAF, NUMA1, EXT2, HRAS, BCL11B, MAGI1, RNF123, NLRP1, ASXL1, ADAMTS20, TAF1L, XPC, DDB2 and ETS1 as mutated genes. The current study could not draw any new conclusions about the relationship between VS-related hearing loss and gene mutations; however, it did reveal that NF2 was the most frequently mutated gene in small sporadic VS.

Millennium-old pathogenic Mendelian mutation discovery for multiple osteochondromas from a Gaelic Medieval graveyard

Only a limited number of genetic diseases are diagnosable in archaeological individuals and none have had causal mutations identified in genome-wide screens. Two individuals from the Gaelic Irish Medieval burial ground of Ballyhanna, Co. Donegal, showed evidence of bone tumours consistent with the autosomal dominant condition multiple osteochondromas. Genome sequencing of the earlier individual uncovered a missense mutation in the second exon of EXT1, a specific lesion that has been identified in several modern patients. The later individual lacked this but displayed a novel frameshift mutation leading to a premature stop codon and loss of function in the same gene. These molecular confirmations of a paleopathological diagnosis within a single rural ancient context are surprisingly disjunct, given the observation of clusters of this disease in modern isolated populations and a de novo mutation rate of only 10%.

NFATC1 and NFATC2 expression patterns in human osteochondromas

Background

Our previous study in genetic mouse models found that NFATc1 and NFATc2 suppress osteochondroma formation from entheseal progenitors. However, it remains unclear whether NFAT signaling is also involved in human osteochondromagenesis. As the first step in addressing this question, the current study aimed to determine the expression patterns of NFATC1 and NFATC2 in human osteochondroma samples.

Methods

Immunohistochemistry (IHC) was used to examine and analyze NFATC1 and NFATC2 expression in human osteochondroma samples. The human periosteum was used to map the expression of NFATC1 under physiological conditions by IHC. Furthermore, human periosteal progenitors were isolated and identified from the periosteal tissues of bone fracture healing patients. The expression of NFATC1 in human periosteal progenitors was characterized by Western blotting compared to human bone marrow stromal cells (BMSC).

Results

The IHC results showed that the expression of NFATC1 was undetectable in most human osteochondromas cells, and only a small proportion of osteochondroma cells, especially clonally grown chondrocytes, showed positive staining of NFATC1. NFATC2 expression was also undetectable in most chondrocytes in human osteochondromas. The mouse and human periosteum showed a comparable ratio of NFATC1 positive cells (9.56 ± 0.80% vs 11.04 ± 2.05%, P = 0.3101). Furthermore, Western blotting analysis revealed that NFATC1 expression was highly enriched in human periosteal progenitors compared to BMSC.

Conclusions

NFATC1 and NFATC2 are undetectable in most human osteochondroma chondrocytes. The expression pattern of NFATC1 in human osteochondromas and the normal periosteum suggests that NFAT signaling could be suppressed during human osteochondromagenesis.

Osteochondroma formation is independent of heparanase expression as revealed in a mouse model of hereditary multiple exostoses

Hereditary multiple exostoses (HME) is a rare, pediatric disorder characterized by osteochondromas that form along growth plates and provoke significant musculoskeletal problems. HME is caused by mutations in heparan sulfate (HS)-synthesizing enzymes EXT1 or EXT2. Seemingly paradoxically, osteochondromas were found to contain excessive extracellular heparanase (Hpse) that could further reduce HS levels and exacerbate pathogenesis. To test Hpse roles, we asked whether its ablation would protect against osteochondroma formation in a conditional HME model consisting of mice bearing floxed Ext1 alleles in Agr-CreER background (Ext1f/f ;Agr-CreER mice). Mice were crossed with a new global Hpse-null (Hpse-/- ) mice to produce compound Hpse-/- ;Ext1f/f ;Agr-CreER mice. Tamoxifen injection of standard juvenile Ext1f/f ;Agr-CreER mice elicited stochastic Ext1 ablation in growth plate and perichondrium, followed by osteochondroma formation, as revealed by microcomputed tomography and histochemistry. When we examined companion conditional Ext1-deficient mice lacking Hpse also, we detected no major decreases in osteochondroma number, skeletal distribution, and overall structure by the analytical criteria above. The Ext1 mutants used here closely mimic human HME pathogenesis, but have not been previously tested for responsiveness to treatments. To exclude some innate therapeutic resistance in this stochastic model, tamoxifen-injected Ext1f/f ;Agr-CreER mice were administered daily doses of the retinoid Palovarotene, previously shown to prevent ectopic cartilage and bone formation in other mouse disease models. This treatment did inhibit osteochondroma formation compared with vehicle-treated mice. Our data indicate that heparanase is not a major factor in osteochondroma initiation and accumulation in mice. Possible roles of heparanase upregulation in disease severity in patients are discussed.

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.

Chondrosarcoma of the toe: A case report and literature review

BACKGROUND

Chondrosarcoma of the foot is a rare malignant bone tumour, and it is even rarer when it originates in a toe bone. Surgical excision is the only effective treatment. The osteolytic destruction of the tumour severely affects limb function and carries the risk of distant metastasis. Most such tumours are removed surgically to minimize local recurrence and distant metastases, maximize limb function, and prolong the patient's tumour-free survival time. The main objective of this article is to present the case of a chondrosarcoma that invaded the first phalanx of the left foot and formed a large phalangeal mass with osteolytic destruction of the distal bone.

CASE SUMMARY

A 74-year-old man suffered from swelling of his left toe for six months, with pain and swelling for two months. Computed tomography and magnetic resonance imaging showed that the tumour on the first phalanx of the left foot was approximately 54.9 mm × 44.6 mm, surrounded by a significant soft tissue signal mass, with osteolytic destruction of the distal phalanx and a speckled bone-like high-density shadow within it.

CONCLUSION

Chondrosarcoma occurring in a toe bone is extremely rare. In this case, extensive surgical resection of the large low-grade chondrosarcoma, which showed osteolytic destruction and invaded the distal metatarsal bone, was safe and effective.

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.

Role of nuclear factor of activated T cells in chondrogenesis osteogenesis and osteochondroma formation

PURPOSE

Nuclear factor of activated T cells (NFATc) are transcription factors that play a function in the immune response and in osteoclast differentiation. In the present work, we define the function of NFATc2 in chondrogenic and osteogenic cells.

METHODS

Nfatc2^loxP/loxP and Nfatc1^loxP/loxP;Nfatc2^loxP/loxP conditional mice were crossed with Prx1-Cre transgenics to inactivate Nfatc2 singly and with Nfatc1. Femurs and vertebrae were examined by microcomputed tomography (µCT) X-Ray images and histology and analyzed for the presence of osteochondromas.

RESULTS

µCT demonstrated that Prx1-Cre;Nfatc2^∆/∆ female mice had transient osteopenia and male mice did not have a cancellous or a cortical bone phenotype when compared to control mice. In contrast, the dual inactivation of Nfatc1 and Nfatc2 in Prx1-expressing cells resulted in cancellous osteopenia and small bones at 1 month of age in both sexes. Nfatc1;Nfatc2 deleted mice exhibited a ~ 50% decrease in bone volume and connectivity. Total bone area, periosteal and endocortical bone perimeters and femoral length were reduced indicating smaller bones. As the mice matured, the shortening of the femoral length persisted, but the osteopenic phenotype resolved and cancellous femoral bone of 4-month-old Nfatc1;Nfatc2 deleted mice was not different from controls although male mice had vertebral osteopenia. In addition, Nfatc1;Nfatc2 deleted mice displayed distortion of the distal metaphysis and, as they matured, the articular presence of mineralized tumors with the appearance of osteochondromas.

CONCLUSION

Our studies reveal that NFATc1 and NFATc2 are necessary for optimal bone homeostasis and the suppression of osteochondroma formation.

Real-World Data and Budget Impact Analysis (BIA): Evaluation of a Targeted Next-Generation Sequencing Diagnostic Approach in Two Orthopedic Rare Diseases

Objective: Next-generation sequencing (NGS) technology, changing the diagnostic approach, has become essential in clinical settings, and its adoption by public health laboratories is now the practice. Despite this, as technological innovations, its intake requires an evaluation of both the clinical utility and the economic investment, especially considering the rare disease scenario. This study evaluated the analytical validity and the budget impact of an NGS-Ion Torrent™ approach for the molecular germline diagnosis of two musculoskeletal rare diseases.

Methods: Two cohorts of 200 and 199 patients with suspect or clinical diagnosis of multiple osteochondromas (MO) and osteogenesis imperfecta (OI) previously evaluated with a single-gene diagnostic protocol were re-analyzed using a targeted NGS assay. Analytical validity was assessed by comparing NGS and single-gene protocol. A budget impact analysis using real-world cost data-considering the healthcare perspective— was performed by applying activity-based costing (ABC). The cost considered consumables, personnel, and equipment. Additional costs not related to NGS activities were not considered. Sensitivity analysis was performed.

Results: The NGS method showed a higher (for MO) and comparable (for OI) diagnostic sensitivity than the traditional techniques, apart from always reducing the time and costs of diagnosis. Overall, the cost saving per patient is € 765 for OI and € 74 for MO. Materials represented the highest cost driver of the NGS process. A time saving—proportional to the panel size—has been assessed in both cases.

Conclusions: Our targeted NGS diagnostic approach decreases time to diagnosis and costs, appearing to be beneficial and recommended both for patients and from a healthcare perspective in routine diagnosis also considering very small gene panels and a low patient flow. The adequate analytical sensitivity always required the additional Sanger sequencing step of the low- and non-covered regions. A more accurate strategy evaluation is suggested in the case of ultra-rare/complex diseases, large gene-panel, or non-reference diagnostic centers.

Lower limb deformities and limb length discrepancies in hereditary multiple exostoses

There is a high rate of lower limb deformity and limb length discrepancy in patients with hereditary multiple exostoses (HME). The aim of this study was to evaluate the type and frequency of lower limbs axial deviation and limb length discrepancy and the type of exostoses being risk factors for theses deformities. We retrospectively reviewed standing full-length radiograph of 32 HME patients (64 limbs) followed in our institution between October 2009 and December 2020. Patient demographics were recorded. Radiographic analysis of the coronal limb alignment was performed, limb length discrepancy was measured and topography of the exostoses was recorded. We propose a classification of lower legs in 2 groups and 4 types according to the presence and the location of exostoses. In group I, there is an intertibio- fibular exostose with fibular origin at the level of the tibiofibular joints. In type IA, at the level of the distal tibiofibular joint with ascension of the distal fibula; in type IB at the level of the proximal tibiofibular joint with a bracketing effect on the proximal tibia and a lateral slope of the proximal tibial growth plate; the type IC is combining features of both IA and IB. In group II, there is no intertibio-fibular exostose coming from the fibula and no growth abnormality is obvious. A clinically notable lower limb discrepancy (LLD) of ≥2 cm was found in 19% of our patients. Approximately 33% of patients had a knee valgus deformity and 44% had an ankle valgus deformity. The knee valgus deformity was due to fibular growth anomalies and not to distal femur anomalies. The majority of lower legs had fibular growth anomalies (72%) which was a significant risk factor for knee valgus deformity and leg length discrepancy. On the contrary, we found no correlation between number, location and volume of distal femoral exostoses and genu valgum nor leg length discrepancy. Presence of intertibio-fibular exostoses is a risk factor for knee valgus deformity and leg length discrepancy. The presence of these exostoses should lead to a close follow-up of the patient.

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.

Characteristics of the length of the radius and ulna in children

OBJECTIVES

Congenital malformation, trauma, tumor, or metabolic disease can cause length deformity of the radius or ulna, affecting the appearance and function of the forearm. Osteotomy and lengthening with external fixation can obviously improve the length of the radius and ulna (LRU). However, the extent of lengthening required is still unclear. This study analyzed the LRU in children, to provide suggested standards for various orthopedic treatments.

METHODS

Normal LRUs were measured on X-ray images in children who came to hospital for emergency treatment, with measurements including anterior-posterior (AP) radiographs, lateral (LAT) radiographs, full LRU (total length), and LRU without the epiphysis (short length). Any cases of fracture or deformity affecting measurement were excluded. Three hundred twenty-six cases were divided into 16 groups according to age from 1 year old to 16 years old.

RESULTS

The earliest epiphyseal plate and ossification center were observed in the distal part of the radius at 1 year old, and in the proximal part at 3 years old in both boys and girls. In the ulna, at the distal end it was 6 years old in girls and 7 years old in boys, while in the proximal part ossification was observed at 9 years old in both boys and girls. The proximal epiphyseal plate of the ulna began to close on X-ray images at 12 years old in girls and 13 years in boys. LRU increased with age, and there was a strong positive correlation and consistent ratio between radius, ulna and age. In short length, the ratio of the length of radius to ulna (RLRU) ranged from 0.8941 to 0.9251 AP, from 0.8936 to 0.9375 LAT. In total length, RLRU ranged from 0.9286 to 0.9508 AP, and 0.9579 to 0.9698 LAT.

CONCLUSIONS

The length and epiphyseal ossification of the radius and ulna are associated with age. RLRU is also limited to a certain range and tends to remain stable with age. These characteristics have clinical significance for deformity correction of the forearm.

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.

Unusual location of osteochondroma in the temporal region in a patient with functional pituitary adenoma

Osteochondromas are common in the long bones and relatively rare in the head and neck regions. We herein report a case of a solitary temporal bone osteochondroma associated with a functional pituitary adenoma hypersecreting prolactin. The patient was a 48-year-old man with progressive, painless temporal swelling associated with gradual visual loss, gynaecomastia, erectile dysfunction, and loss of libido. A brain computed tomography scan with bone windows showed right temporal sessile bony expansion and a pituitary tumour. A pituitary function test revealed hyperprolactinaemia. His symptoms resolved with medical management, and excisional biopsy of the temporal tumour confirmed an osteochondroma. To the best of our knowledge, this is the first reported case of a solitary temporal bone osteochondroma with a functional pituitary adenoma hypersecreting prolactin.

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.

Multiple Osteochondromas Comorbid With Enlarged Parietal Foramina, Elongated Styloid Processes, and Tibiofibular Synostosis

OBJECTIVES

This study investigates a unique case of multiple osteochondromas (MO) comorbid with enlarged parietal foramina and correlates the findings with the existing literature. The aim of this study is to provide a deeper understanding of anatomic variation for physicians.

METHODS

A 66-year-old White male donor was examined during a routine cadaveric dissection performed by medical students in an anatomy laboratory. Detailed exploration of the skeleton and organs was performed, and photographs were taken. Tissue samples were obtained from multiple outgrowths, and histopathologic examination was done.

RESULTS

Bilateral bony growths were noted rising from the long bones of the upper and lower extremities (femur, tibia, fibula, and radius). An accessory muscle was found to be associated with the left radial bony growth. Histopathologic examination was positive for osteochondroma. Inspection of the skull revealed enlarged parietal foramina. Other findings included tibiofibular synostosis, abnormally shaped vertebral bodies and ribs, and elongated styloid processes of the skull.

CONCLUSIONS

In combination with the histopathologic examination, the case report and literature review elucidate a more precise clinical picture for those affected with MO or similar disorders. This report also emphasizes the necessity of further investigation of the pathogenesis of MO and Potocki-Shaffer syndrome.

Natural History and Characteristics of Hand Exostoses in Multiple Hereditary Exostoses

PURPOSE

Multiple hereditary exostoses (MHEs) comprise a rare skeletal disorder. This study aimed to elucidate the natural history and characteristics of hand exostoses by focusing on their progression or regression and their association with shortening and angular deformation of the finger bones.

METHODS

Of 60 MHE patients who presented to our hospital between 2005 and 2019, 32 patients (62 hands) who underwent hand x-ray examinations were included in a study of initial presentation. Among them, 15 patients (30 hands) who underwent consecutive x-ray examinations before epiphyseal closure were included in a subsequent follow-up study (follow-up period, 6.9 years). We investigated the incidence and common location of hand involvement by exostoses during the initial examination study. We further investigated the progression or regression of hand exostoses and the influence of hand exostoses on longitudinal bone growth and the angular deformation of finger bones during the follow-up study.

RESULTS

In the initial study, we observed exostoses in 30 (60 hands) of 32 (62 hands) patients. The average number of exostoses per hand was 5.2. Exostoses developed more frequently in the middle and ring proximal phalanges and the fifth metacarpal. In the follow-up study, 3.1 exostoses per hand spontaneously regressed and 2.9 exostoses per hand occurred de novo with growth. Progression of exostoses was mainly observed by approximately age 15 years; thereafter, spontaneous regression became dominant. Regression of exostoses was frequently observed in metacarpals, whereas de novo exostoses frequently occurred in phalangeal bones, particularly in distal phalanges. Growth plate involvement by exostoses did not influence the longitudinal growth of finger bones, but it increased their angulation.

CONCLUSIONS

The hand is a common location of exostoses development for MHE patients. Although some exostoses in the hands regress with skeletal maturity, hand involvement by exostoses can result in angular deformity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic IV.

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.

Reconstruction of the Hip in Multiple Hereditary Exostoses

The hip joint involvement in multiple hereditary exostoses (MHE) occurs in 30-90%, causing pain and limitation of motion by femoroacetabular impingement, coxa valga, acetabular dysplasia, hip joint subluxation, and osteoarthritis. The purpose of this study was to investigate the clinical and radiographic outcomes of ten hips in seven patients treated by surgical dislocation and corrective osteotomies between 2004 and 2009. Surgical dislocation and excision of the osteochondromas and varus intertrochanteric osteotomies were performed in all cases when the neck-shaft angle was > 150°. Common sites of osteochondromas were medial, posterior, and anterior neck of the femur. Neck-shaft angle of the femur was improved from a mean of 157° to 139°, postoperatively. On an average, the center-edge angle improved from 20° to 30° postoperatively. We believe that Ganz's safe surgical dislocation technique is the preferred treatment of MHE. This safeguards the circulation of the femoral head and the osteochondromas can be resected under direct vision. It can be combined with additional corrective osteotomies because the hip affected by MHE is frequently associated with dysplastic changes which can result in premature osteoarthritis.

Congenital and Developmental Abnormalities of the Hand and Wrist

Identification of congenital skeletal abnormalities is complex because of the large variety of individual syndromes and dysplasias that are often difficult to remember. Although a correct diagnosis relies on a combination of clinical, radiologic, and genetic tests, imaging plays an important role in selecting those patients who should be referred for further genetic counseling and expensive genetic tests. In addition to information derived from radiologic analysis of other skeletal elements, radiographs of the hand and wrist may provide particular useful information. In the first part of this article, we provide a guide for a systematic radiologic analysis of the hand and wrist bones that may help characterize congenital and developmental diseases. Special attention is given to the use of correct terminology. In the second part, we discuss typical examples of congenital and developmental diseases involving the hand and wrist, with an emphasis on skeletal dysplasias.

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.

Rib osteochondroma causing cardiac compression in a pediatric patient

•

Osteochondromas are considered the most common benign tumors of bony origin.

•

Exostosis are slow growing masses usually diagnosed before the third decade of life.

•

A computed tomography scan offers a more accurate tool in the diagnosis of this type of condition.

•

Rib exostosis occurs more frequently in males than females with a ratio of 1.5:1.

•

Costal osteochondromas mostly occur as a part of hereditary multiple osteochondromas.

Introduction and importance

Rib osteochondromas are rare genetic disorders, which can present as bony exostosis causing compression, impingement and damage to surrounding vessels, organs and structures within the thoracic cavity. The objective of this study was to clearly describe a rare presentation of rib osteochondromas in a pediatric patient along with managing techniques.

Case

A 9-year-old girl was admitted to the hospital due to shortness of breath on exertion. Physical examination did not reveal any abnormalities except for small bony projections over the left 5th rib. Computed tomography (CT) scan showed a bony lesion on the left fifth rib causing cardiac compression. Video-assisted thoracoscopy (VAT) was done, which showed a bony exostosis compressing the left ventricle, the lesion was resected without any complications. Final pathology confirmed the diagnosis of osteochondroma measuring 2.0 cm × 2.0 cm × 1.5 cm, along with a thickness of 0.4 cm. Post-operative recovery was well, with no morbidities and the patient was discharged without any complications. On the post-operative follow up, the patient showed significant improvement in her symptoms.

Clinical discussion

Our reported case is a rare example of a solitary costal osteochondroma leading to serious complications because of its shape, size, and location. Previous reports have not addressed any significant traumatic event or impact prior to the occurrence of symptoms related to the cases, including the case of our patient. Cases of rib exostosis were surgically approached using different techniques most often through thoracotomy.

Conclusions

Rib osteochondromas are rare benign bony lesions which can cause cardiac symptoms secondary to direct compression. They can be resected safely via video assisted thoracoscopy (VAT) or limited thoracotomy.

Mutation spectrum of EXT1 and EXT2 in the Saudi patients with hereditary multiple exostoses

BACKGROUND

Hereditary Multiple Exostoses (HME), also known as Multiple Osteochondromas (MO) is a rare genetic disorder characterized by multiple benign cartilaginous bone tumors, which are caused by mutations in the genes for exostosin glycosyltransferase 1 (EXT1) and exostosin glycosyltransferase 2 (EXT2). The genetic defects have not been studied in the Saudi patients.

AIM OF STUDY

We investigated mutation spectrum of EXT1 and EXT2 in 22 patients from 17 unrelated families.

METHODS

Genomic DNA was extracted from peripheral leucocytes. The coding regions and intron-exon boundaries of both EXT1 and EXT2 genes were screened for mutations by PCR-sequencing analysis. Gross deletions were analyzed by MLPA analysis.

RESULTS

EXT1 mutations were detected in 6 families (35%) and 3 were novel mutations: c.739G > T (p. E247*), c.1319delG (p.R440Lfs*4), and c.1786delA (p.S596Afs*25). EXT2 mutations were detected in 7 families (41%) and 3 were novel mutations: c.541delG (p.D181Ifs*89), c.583delG (p.G195Vfs*75), and a gross deletion of approximately 10 kb including promoter and exon 1. Five patients from different families had no family history and carried de novo mutations (29%, 5/17). No EXT1 and EXT2 mutations were found in the remaining four families. In total, EXT1 and EXT2 mutations were found in 77% (13/17) of Saudi HME patients.

CONCLUSION

EXT1 and EXT2 mutations contribute significantly to the pathogenesis of HME in the Saudi population. In contrast to high mutation rate in EXT 1 (65%) and low mutation rate in EXT2 (25%) in other populations, the frequency of EXT2 mutations are much higher (41%) and comparable to that of EXT1 among Saudi patients. De novo mutations are also common and the six novel EXT1/EXT2 mutations further expands the mutation spectrum of HME.

Identification of Two Novel Frameshift Mutations in Exostosin 1 in Two Families with Multiple Osteochondromas

Multiple osteochondromas (MO) is an autosomal dominant hereditary disorder, which typically manifests as skeletal dysplasia, mainly involving long bones and knees, ankles, elbows, wrists, shoulders, and pelvis. Previous studies have demonstrated that mutations in exostosin glycosyl transferase-1 (EXT1) and exostosin glycosyl transferase-2 (EXT2) were the main cause of MO. In this study, we enrolled 2 families with MO. Sanger sequencing revealed 2 novel frameshift mutations - c.1432_1433insCCCCCCT; p.Lys479Profs*44 and c.1431_1431delC; p.S478PfsX10 - in the EXT1 gene detected in 2 families, respectively. Both novel mutations, located in the conserved domain of EXT1 and predicted to be disease causing by informatics programs, were absent in our 200 control cohorts and other public databases. Our study expanded the spectrum of EXT1 mutations and contributed to genetic diagnosis and counseling of patients with MO.

Diagnosis, Management, and Treatment Options: A Cervical Spine Osteochondroma Meta-Analysis

Osteochondroma is described as a capped benign bony neoplasm that forms on the outer surface of bone. These tumors affect nearly 6 million people per year. Although osteochondromas most often involve the appendicular skeleton, many involve the spine, with many cases located in the cervical spine. When osteochondromas involve the spine, they can present with a variety of symptoms, including pain, radiculopathy, and myelopathy, which may necessitate surgical treatment. Spinal osteochondromas can be classified into 2 types: multiple osteochondromas in the context of patients with multiple hereditary exostosis (MHE) and solitary osteochondroma or solitary exostosis (SE). Previous reviews have captured only some of the available literature on cervical osteochondromas and have generally focused on either SE or those associated with MHE. The purpose of our review was to provide an extensive review of all previously reported cervical osteochondromas and to compare osteochondroma characteristics, clinical presentation, and outcomes in the context of MHE and SE.

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.

Learning from BMPs and their biophysical extracellular matrix microenvironment for biomaterial design

It is nowadays well-accepted that the extracellular matrix (ECM) is not a simple reservoir for growth factors but is an organization center of their biological activity. In this review, we focus on the ability of the ECM to regulate the biological activity of BMPs. In particular, we survey the role of the ECM components, notably the glycosaminoglycans and fibrillary ECM proteins, which can be promoters or repressors of the biological activities mediated by the BMPs. We examine how a process called mechano-transduction induced by the ECM can affect BMP signaling, including BMP internalization by the cells. We also focus on the spatio-temporal regulation of the BMPs, including their release from the ECM, which enables to modulate their spatial localization as well as their local concentration. We highlight how biomaterials can recapitulate some aspects of the BMPs/ECM interactions and help to answer fundamental questions to reveal previously unknown molecular mechanisms. Finally, the design of new biomaterials inspired by the ECM to better present BMPs is discussed, and their use for a more efficient bone regeneration in vivo is also highlighted.

A mutation in SLC20A2 (c.C1849T) promotes proliferation while inhibiting hypertrophic differentiation in ATDC5 chondrocytes

AIMS

This study aimed to investigate the effect of solute carrier family 20 member 2 (SLC20A2) gene mutation (identified from a hereditary multiple exostoses family) on chondrocyte proliferation and differentiation.

METHODS

ATDC5 chondrocytes were cultured in insulin-transferrin-selenium medium to induce differentiation. Cells were transfected with pcDNA3.0 plasmids with either a wild-type (WT) or mutated (MUT) SLC20A2 gene. The inorganic phosphate (Pi) concentration in the medium of cells was determined. The expression of markers of chondrocyte proliferation and differentiation, the Indian hedgehog (Ihh), and parathyroid hormone-related protein (PTHrP) pathway were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting.

RESULTS

The expression of SLC20A2 in MUT group was similar to WT group. The Pi concentration in the medium of cells in MUT group was significantly higher than WT group, which meant the SLC20A2 mutation inhibited Pi uptake in ATDC5 chondrocytes. The proliferation rate of ATDC5 chondrocytes in MUT group was greater than WT group. The expression of aggrecan (Acan), α-1 chain of type II collagen (COL2A1), and SRY-box transcription factor 9 (SOX9) were higher in MUT group than WT group. However, the expression of Runt-related transcription factor 2 (Runx2), α-1 chain of type X collagen (COL10A1), and matrix metallopeptidase 13 (MMP13) was significantly decreased in the MUT group. Similar results were obtained by Alcian blue and Alizarin red staining. The expression of Ihh and PTHrP in MUT group was higher than WT group. An inhibitor (cyclopamine) of Ihh/PTHrP signalling pathway inhibited the proliferation and restored the differentiation of chondrocytes in MUT group.

CONCLUSION

A mutation in SLC20A2 (c.C1948T) decreases Pi uptake in ATDC5 chondrocytes. SLC20A2 mutation promotes chondrocyte proliferation while inhibiting chondrocyte differentiation. The Ihh/PTHrP signalling pathway may play an important role in this process. Cite this article: Bone Joint Res 2020;9(11):751-760.

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.

The natural history of multiple osteochondromas in a large Italian cohort of pediatric patients

IMPORTANCE

Multiple osteochondromas is a rare hereditary skeletal disorder, characterized by bony protrusions arising from growth plates on long bones during skeletal development. The disorder frequently leads to diminished stature, deformities and functional limitations. Understanding of the natural history of multiple osteochondromas and its evolution in children and adolescents is limited.

OBJECTIVE

To provide valuable information on the natural history of multiple osteochondromas, to inform recommendations for treatment and prevent impairments caused by osteochondromas.

DESIGN

This retrospective cohort study in children with multiple osteochondromas includes longitudinal data collected from first to last follow-up visit for patient demographics, and over 36 months for disease evolution.

SETTING

Data were collected from the Registry of Multiple Osteochondromas, which includes data from circa 1200 patients with multiple osteochondromas treated from 2003 to 2017 at IRCCS Istituto Ortopedico Rizzoli in Bologna.

PARTICIPANTS

Patients ≤18 years with multiple osteochondromas, who provided written informed consent and had data for ≥1 12-month follow-up visit.

MAIN OUTCOME(S) AND MEASUREMENT(S)

Demographics, clinical features, incidence of surgeries, and disease evolution (progression or regression) were assessed. Results were summarized using descriptive statistics, annual rates of new clinical features and surgeries, and Kaplan-Meier estimates. Patient height was evaluated following Italian growth charts.

RESULTS

158 patients were included in these analyses. Throughout follow-up, 80.4% of patients developed new osteochondromas, 57.6% developed new deformities, 23.4% developed new functional limitation(s). New osteochondroma(s) were developed by 28.5% patients by Month 12, 39.9% at Month 24, 50% at Month 36. Most new osteochondromas were detected in the younger population; patients aged 0-4 years underwent a significantly higher number of lesions within 12, 24 and 36 months of follow-up. The overall incidence of patients with ≥1 new deformity within 12 months was 17.7%, with incidences decreasing with increasing age (p = .023). In addition, the analyses on height highlight that 13 years is a cut off age for slow growth of the stature (p < .0005). At last follow-up visit, 46.2% of patients had disease progression, while regression (spontaneous and surgical) occurred in 7.6% (p = .007).

CONCLUSIONS AND RELEVANCE

This natural history study reports the main set of clinically relevant data for patients with multiple osteochondromas during skeletal development, providing insight for patient management and development of therapeutic interventions.

Accelerometer-Based, Computer-Navigated Total Knee Arthroplasty to Correct a Complex Deformity in a Patient With Multiple Hereditary Exostoses

Background

Accelerometer-based computer-assisted navigation systems (ABCANSs) have been shown to improve alignment accuracy in total knee arthroplasty (TKA) and are effective in treating complex extra-articular deformity. We present an ABCANS-assisted TKA performed in a 68-year-old male with end-stage arthritis of the right knee, in the setting of a severe valgus deformity secondary to multiple hereditary exostoses.

Methods

The KneeAlign 2 system (OrthAlign, Inc.; Aliso Viejo, CA) was used to perform the TKA in this clinical scenario, given its functionality, which allows angular correction to be tailored to a given deformity, and its reported accuracy in performance of bony resection in TKA. The patient was prospectively followed up for one year postoperatively. Radiographs, PROMs, and patient satisfaction were reported.

Results

After the ABCANS-assisted TKA, the patient's alignment was improved from 25° to 4° of valgus. His final range of motion was 0-135° without an instability. In addition, the patient reported excellent scores on multiple joint-specific outcome measures, including the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, the Forgotten Joint Score, and the Oxford Knee Score.

Conclusion

This case report illustrates the rationale, technique, and the excellent clinical outcomes achieved in a complex patient with extra-articular deformity using an ABCANS-assisted TKA.

Whole‑exome sequencing identifies a novel mutation of SLC20A2 (c.C1849T) as a possible cause of hereditary multiple exostoses in a Chinese family

Although the main causative genes for hereditary multiple exostoses (HME) are exostosin (EXT)‑1 and EXT‑2, there are numerous patients with HME without EXT‑1 and EXT‑2 mutations. The present study aimed to identify novel candidate genes for the development of HME in patients without EXT‑1 and EXT‑2 mutations. Whole‑exome sequencing was performed in a Chinese family with HME and without EXT‑1 and EXT‑2 mutations, followed by a combined bioinformatics pipeline including annotation and filtering processes to identify candidate variants. Candidate variants were then validated using Sanger sequencing. A total of 1,830 original variants were revealed to be heterozygous mutations in three patients with HME which were not present in healthy controls. Two mutations [c.C1849T in solute carrier family 20 member 2 (SLC20A2) and c.G506A in leucine zipper and EF‑hand containing transmembrane protein 1 (LETM1)] were identified as possible causative variants for HME through a bioinformatics filtering procedure and harmful prediction. Sanger sequencing results confirmed these two mutations in all patients with HME. A mutation in SLC20A2 (c.C1849T) led to a change in an amino acid (p.R617C), which may be involved in the development of HME by inducing metabolic disorders of phosphate and abnormal proliferation and differentiation in chondrocytes. In conclusion, the present study revealed two mutations [SLC20A2 (c.C1849T) and LETM1 (c.G506A) in a Chinese family with HME. The mutation in SLC20A2 (c.C1849T)] was more likely to be involved in the development of HME.