Pediatric diaphragmatic hernia induced by a rib osteochondroma

Diaphragmatic hernia in children is uncommon, especially when not congenital. We present a case of an 11-year old boy with a diaphragmatic hernia caused by a rib osteochondroma. The osteochondroma was surgically removed and the laceration in the diaphragm was repaired. This case shows the importance of being familiar with acquired diaphragmatic hernia in children, to recognize and prevent possible complications in an early stage.

Chondrosarcoma secondary to hereditary multiple osteochondromas with spinal cord compression: A case report and systematic review

Background

Hereditary multiple osteochondromas (HMOs) are a rare genetic disorder characterized by the formation of multiple benign osteochondromas that can undergo malignant transformation into chondrosarcoma.

Case Description

A 24-year-old male with a history of HMO and osteochondroma surgery 4 years ago, presented with back pain and paresthesias. The magnetic resonance showed a right paravertebral infiltrating mass at the T12-L1 level causing spinal cord compression. Following en bloc resection of the tumor, the patient's symptoms/ signs resolved. The final pathological diagnosis was consistent with a chondrosarcoma.

Conclusion

Chondrosarcomas secondary to HMO with spinal cord compression are rare. These patients often presenting with significant myelopathy/cord compression should undergo gross total resection where feasible to achieve the best outcomes.

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.

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.

Spontaneous pneumothorax in a 17-year-old male patient with multiple exostoses: A case report and review of the literature

BACKGROUND

Multiple exostoses generally develop in the first decade of life. They most frequently arise from the distal femur, proximal tibia, fibula, and proximal humerus. Costal exostoses are rare, contributing to 1%–2% of all exostoses in hereditary multiple exostoses (HME). They are usually asymptomatic, but a few cases have resulted in severe thoracic injuries. Pneumothorax caused by costal exostoses is rare, with only 13 previously reported cases. We report a new case of pneumothorax caused by costal exostoses.

CASE SUMMARY

A 17-year-old male with HME underwent surgery for removal of exostoses around his right knee. Four months following the operation, he felt chest pain when he was playing the trumpet; however, he did not stop playing for a week. He was referred to our hospital with a chief complaint of chest pain. The computed tomography (CT) scan revealed right pneumothorax and multiple exostoses in his right ribs. The CT scan also revealed visceral pleura thickness and damaged lung tissues facing the exostosis of the seventh rib. We diagnosed that exostosis of the seventh rib induced pneumothorax. Costal exostosis resection was performed by video-assisted thoracoscopic surgery (VATS) 2 wk after the onset. The patient’s postoperative course was uneventful, and there was no recurrence of pneumothorax for 2 years.

CONCLUSION

Costal exostoses causing thoracic injuries should be resected regardless of age. VATS must be considered in cases with apparently benign and relatively small exostoses or HME.

C1 C2 spinal cord compression in hereditary multiple exostoses: case report and review of the literature

INTRODUCTION AND IMPORTANCE

Hereditary multiple exostoses (HME) is a benign disease, usually encountered in the metaphysis of long bones. On the opposite, spinal localizations are very rare. We herein describe a case of HME with a spinal cord compression.

CASE PRESENTATION

A 31-years-old patient with a history of HME, presented with signs of cervical spinal cord compression that progressively appeared in the last 10 years. Cervical MRI and CT scan showed a compressive osseous tumor arising from the surface of the right side of the dorsal arch of the axis. Our patient underwent C1C2 laminectomy, but no clinical improvement has been recorded postoperatively.

CLINICAL DISCUSSION

Spinal cord compression is an extremely serious complication of hereditary multiple exostoses (HME). The cervical and thoracic areas were predominantly affected, with the symptoms usually developing slowly. Early surgery is correlated to good postoperative outcomes.

CONCLUSION

Despite its rarity, HME should be considered as a possible cause for spinal cord compression.

Distinct osmoregulatory responses to sodium loading in patients with altered glycosaminoglycan structure: a randomized cross-over trial

Background

By binding to negatively charged polysaccharides called glycosaminoglycans, sodium can be stored in the body—particularly in the skin—without concurrent water retention. Concordantly, individuals with changed glycosaminoglycan structure (e.g. type 1 diabetes (DM1) and hereditary multiple exostosis (HME) patients) may have altered sodium and water homeostasis.

Methods

We investigated responses to acute (30-min infusion) and chronic (1-week diet) sodium loading in 8 DM1 patients and 7 HME patients in comparison to 12 healthy controls. Blood samples, urine samples, and skin biopsies were taken to investigate glycosaminoglycan sulfation patterns and both systemic and cellular osmoregulatory responses.

Results

Hypertonic sodium infusion increased plasma sodium in all groups, but more in DM1 patients than in controls. High sodium diet increased expression of nuclear factor of activated t-cells 5 (NFAT5)—a transcription factor responsive to changes in osmolarity—and moderately sulfated heparan sulfate in skin of healthy controls. In HME patients, skin dermatan sulfate, rather than heparan sulfate, increased in response to high sodium diet, while in DM1 patients, no changes were observed.

Conclusion

DM1 and HME patients show distinct osmoregulatory responses to sodium loading when comparing to controls with indications for reduced sodium storage capacity in DM1 patients, suggesting that intact glycosaminoglycan biosynthesis is important in sodium and water homeostasis.

Trial registration These trials were registered with the Netherlands trial register with registration numbers: NTR4095 (https://www.trialregister.nl/trial/3933 at 2013-07-29) and NTR4788 (https://www.trialregister.nl/trial/4645 at 2014-09-12).

An analysis of osteoporosis in patients with hereditary multiple exostoses

We analyzed osteoporosis in 20 HME patients. According to the T-score of BMD, 30% and 67.5% of the patients fell in the range of osteopenia in the lumbar spine and femoral neck. Our results indicate HME patients have low bone mass. They do not have abnormal bone metabolism.

INTRODUCTION

There are few reports of osteoporosis in hereditary multiple exostoses (HME) patients. Therefore, the purpose of this study was to analyze osteoporosis in HME patients.

METHODS

This retrospective cohort study included 20 patients diagnosed with HME. Patients underwent bone mineral density (BMD) measurement of the lumbar spine (n = 20) and femoral neck (n = 40). Bone metabolic parameters, including serum osteocalcin and urinary cross-linked N-telopeptide of type 1 collagen (NTx), were analyzed in all subjects. EXT1 and EXT2 genes were sequenced using genomic DNA. We also examined the correlation between genotype and BMD Z-score and T-score.

RESULTS

The mean BMD values of the lumbar spine were 1.085 ± 0.116 g/cm² (n = 11) in male and 1.108 ± 0.088 g/cm² (n = 9) in female. The mean BMD values of the femoral neck area were 0.759 ± 0.125 g/cm² (n = 22) in male and 0.749 ± 0.115 g/cm² (n = 18) in female. Z-score of most HME patients show < 0, indicating that these patients tend to have low bone mass compared with the age-matched population. According to the T-score of BMD, 30% (6 of 20) and 67.5% (27 of 40) of the patients fell in the range of osteopenia in the lumbar spine and femoral neck areas, respectively. Serum osteocalcin and urinary NTx were in the normal range in most patients. There was no significant correlation between genotypes and Z-score.

CONCLUSION

HME patients have low bone mass, especially in the femoral neck area. They do not have abnormal bone metabolism, and there was no correlation between genotypes and Z-score.

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.

Total knee arthroplasty with simultaneous tibial shaft osteotomy in patient with multiple hereditary osteochondromas and multiaxial limb deformity - a case report

BACKGROUND

Hereditary multiple osteochondromas (hereditary multiple exostoses, HME) is a rare genetic disease characterized by the development of benign osteocartilaginous tumors that may cause severe limb deformities and early onset osteoarthritis. Total knee arthroplasty (TKA) is the method of choice for the treatment of advanced gonarthrosis, however the surgical management with coexisting severe axial limb deformity remains unclear.

CASE PRESENTATION

65-year-old man with HME and extra-articular multi-axial limb deformity was admitted to the orthopedic department due to chronic knee pain and limited range of motion caused by secondary osteoarthritis. Regarding to the clinical and radiological examinations, after preoperative planning he was qualified to a one-stage TKA combined with tibial shaft osteotomy (TSO). In a one year follow-up full bone union was confirmed with no signs of implant loosening or prosthesis displacement. Patient was very satisfied, did not report any joint pain and has sufficient range of motion without knee instability.

CONCLUSION

The improvement of mechanical axis during TKA is a crucial factor for achieve operative success and long implant survival. Despite the higher risk of complication rate in comparison to two-stage treatment, one-stage TKA with simultaneous TSO should be a considerable method for patients with osteoarthritis and multiaxial limb deformities. This method can give a good clinical and functional outcomes, however should be performed subsequently to careful preoperative planning and proper patient qualification.

Osteochondroma of the Distal Clavicle: A Rare Cause of Impingement and Biceps Tear of the Shoulder

Hereditary multiple exostosis (HME) is an autosomal dominant disorder manifested by the presence of multiple osteochondromas. Although the lesions are benign in nature, exostoses are often associated with characteristic progressive skeletal deformity and displaying clinical symptoms such as mechanical irritation or impingement. We present the successful arthroscopic resection in a 24-year-old HME male with impingement syndrome and long head tendon tear of the biceps caused by osteochondroma arising from the distal clavicle.

Effect of multiple hereditary exostoses on sports activity in children

Objective

The purpose of this clinical case-control study was to assess the level of sports activity in children with hereditary multiple exostoses (HME) and to compare with the degree of physical activity in children of the same age without pathology.

Methods

A case-control study was designed. Cases were drawn from children with HME diagnosed on the basis of clinical and radiographic evaluation with an age less then 12 years. Controls were chosen from a group of children with the same age and a negative family history for HME. All patients and controls were completed with the help of parents using the following evaluations: Tegner Activity Level Scale and University of California Los Angeles (UCLA) activity scale.

Results

A total of 154 individuals participated (54 cases and 100 controls). In the case groups, the mean age was 9.07; the mean number of exostoses resulted 29.51, while the mean value of UCLA and Tegner score resulted respectively 6.04 and 5.09. In the controls, the mean age was 8.88; mean UCLA and Tegner resulted respectively 7.17 and 5.64. Comparing the two groups, the only difference was between UCLA score (p = 0.0053). Moreover, comparing the results between female children affected by HME and female controls, we found a significant difference as regards UCLA score (p = 0.0045).

Conclusion

Children affected by HME reported lower sports activity, in particular as regards female patients. Moreover, physical activity is not correlated with any other independent factor leading different patients to a similar level of ability in performing sport.

Study design

Level III - Case Control Study.

A genotype-phenotype study of hereditary multiple exostoses in forty-six Chinese patients

BACKGROUND

Hereditary multiple exostoses (HME) is a rare autosomal dominant skeletal disorder that can cause a variety of clinical manifestations. We aimed to evaluate the general clinical phenotypic severity of HME by using a scoring system and correlate the genotypes with different clinical phenotypes in Chinese patients.

METHODS

Forty-six patients from different families were prospectively enrolled. The mutations were identified by direct sequencing of PCR-amplified genomic DNA or by multiplex ligation-dependent probe amplification (MLPA). Patients' demographic data, height, age of onset, number of anatomical sites, forearm deformity, and lower extremity alignment were analysed according to genotype and gender. A scoring system was used to assess the severity of the clinical phenotype.

RESULTS

Thirty (60%) patients presented mutations in the EXT1 gene, and 16 (32%) presented mutations in the EXT2 gene. The mean age of onset was 2.96 years. The mean number of involved anatomic sites was 15.35. Male patients had more lesion sites than female patients (15.97 vs. 13.77, p = 0.046). The height evaluation illustrated that 67% of the patients (31 of 46) were below the 50th percentile, and the patients with EXT1 mutations were shorter than those with EXT2 mutations (p = 0.005). Forearm deformity showed a significant correlation with the number of involved anatomical sites (r = 0.382, p = 0.009). Moreover, a higher total score was found in patients with EXT1 mutations (p = 0.001).

CONCLUSIONS

The clinical manifestations of 46 Chinese HME patients were similar to those in previous reports of Western populations. Patients with EXT1 mutations have a more severe clinical phenotype than patients with EXT2 mutations.

Hereditary multiple exostoses as a novel cause of bilateral popliteal artery aneurysms in the elderly

Hereditary multiple exostoses (HME) is a genetic condition characterized by the development of multiple osteochondromas during childhood and adolescence. On rare occasions, these bony tumors can be associated with vascular injury, most commonly involving the popliteal artery. Such patients typically present with vascular complications in adolescence and young adulthood. We report an autopsy study of an elderly man who presented with bilateral popliteal artery pseudoaneurysms in the setting of HME at age 81. This is the oldest patient presenting with a vascular complication due to HME reported to date, as well as the only known case of bilateral popliteal pseudoaneurysms caused by HME. This is also the only autopsy study of this vascular complication so far reported. Our case illustrates that vascular complications from HME can occur even in the elderly, and may show bilateral involvement.

Pes Anserinus Syndrome Caused by Osteochondroma in Paediatrics: A Case Series Study

Introduction:

Osteochondroma is a common benign bone tumor, protruding from the underlying normal bone. Osteochondromas can cause pain depending on their location and size. The pes anserinus is located at the proximal medial side of the tibia, where the tendinous insertions of the sartorius, gracilis and semitendinosus muscles collectively attach. Pes anserinus syndrome, or anserine bursitis, is a painful condition of the pes anserinus, and is more common in adults typically with overweight females. The occurrence of pes anserinus syndrome is rare in the paediatric population.

Results:

In the current case series, five patients with pes anserinus syndrome due to proximal tibial osteochondroma are reported. Pain was present in all cases, with snapping in one case. The average age of the patients was 13 ± 1.2 years, ranging from 12 to 15 years. Three patients had a single osteochondroma, and two patients had hereditary multiple exostoses. The sizes of the osteochondromas on plain radiographs varied from 0.5 to 2.5 cm, with an average of 1.46 ± 0.83 cm. All lesions characteristically were located at the medial-posterior edge of the proximal tibia. The symptoms resolved in four cases with surgical resection, and persisted in one non-resected patient.

Conclusion:

The characteristic location of the osteochondroma causes pes anserinus syndrome, even though the lesion is small. The diagnosis of osteochondroma or pes anserinus syndrome may be overlooked when it occurs in a paediatric population. The symptoms seem to be consistent, and resection of the osteochondroma is necessary for treatment.

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

PURPOSE OF REVIEW

Hereditary multiple exostoses (HME) is a complex musculoskeletal pediatric disorder characterized by osteochondromas that form next to the growth plates of many skeletal elements, including long bones, ribs, and vertebrae. Due to its intricacies and unresolved issues, HME continues to pose major challenges to both clinicians and biomedical researchers. The purpose of this review is to describe and analyze recent advances in this field and point to possible targets and strategies for future biologically based therapeutic intervention.

RECENT FINDINGS

Most HME cases are linked to loss-of-function mutations in EXT1 or EXT2 that encode glycosyltransferases responsible for heparan sulfate (HS) synthesis, leading to HS deficiency. Recent genomic inquiries have extended those findings but have yet to provide a definitive genotype-phenotype correlation. Clinical studies emphasize that in addition to the well-known skeletal problems caused by osteochondromas, HME patients can experience, and suffer from, other symptoms and health complications such as chronic pain and nerve impingement. Laboratory work has produced novel insights into alterations in cellular and molecular mechanisms instigated by HS deficiency and subtending onset and growth of osteochondroma and how such changes could be targeted toward therapeutic ends. HME is a rare and orphan disease and, as such, is being studied only by a handful of clinical and basic investigators. Despite this limitation, significant advances have been made in the last few years, and the future bodes well for deciphering more thoroughly its pathogenesis and, in turn, identifying the most effective treatment for osteochondroma prevention.

The impact of hereditary multiple exostoses on quality of life, satisfaction, global health status, and pain

PURPOSE

The aim of the study was to evaluate quality of life (QOL), global health status, pain, and level of satisfaction in patients with hereditary multiple exostoses (HME), and to correlate the association between the severity of diseases and age, sex, number of surgical procedures, and number of exostoses.

METHODS

The data of 50 patients with HME were retrospectively evaluated and recorded. QOL was evaluated with the Short-Form Health Survey (SF-12) questionnaire, the 12-Item General Health Questionnaire (GHQ-12), and Quality of Life Enjoyment and Satisfaction Questionnaire (Q-LES-Q-SF); intensity of pain was measured using the visual analogue scale (VAS). The association of age, gender, pain, quality of life, number of exostoses, and number of surgical procedures were evaluated and correlated.

RESULTS

Mean number of exostoses in our patient's cohort resulted 18.12 ± 8.60, and every patient underwent to a mean of 5.62 ± 5.74 surgical procedures for the exostoses. Mean VAS resulted 5.16 ± 2.90. Considering SF-12, mental (MCS) and physical (PCS) component resulted, respectively, 45.36 ± 10.76 and 38.73 ± 11.09, while GHQ-12 and Q-LES-Q-SF were 15.48 ± 4.70 and 45.28 ± 9.55, respectively. We found a significant positive correlation between the number of exostoses and the number of surgical procedures (p < 0.001), a significant positive correlation between the number of surgical procedures and GHQ-12 (p = 0.422) and VAS (p = 0.0011), and a negative correlation between the number of surgical procedures and PCS (p = 0.0257) and between age and GHQ-12 (p = 0.0385).

CONCLUSIONS

We can conclude that HME impact on patient quality of life as measured by the MCS and PCS scores similar to the disability associated with osteoarthritis in the mental component and tumors or diabetes as regards the physical component. Moreover, we found no difference in patients' quality of life as regards number of exostoses, age, and surgical procedure, but we found that women have a worse response as regards the psychological side than men.

Assessing the general population frequency of rare coding variants in the EXT1 and EXT2 genes previously implicated in hereditary multiple exostoses

Hereditary multiple exostoses (HME) is a rare childhood-onset skeletal disease linked to mutations in exostosin glycosyltransferase 1 (EXT1) or 2 (EXT2). Patients are heterozygous for either an EXT1 or EXT2 mutation, and it is widely assumed that exostosis formation and associated defects, such as growth retardation and skeletal deformities, require loss-of-heterozygosity or a second hit in affected cells. However, the relevance and phenotypic impact of many presumed pathogenic EXT variants remain uncertain. We extracted all amino acid-altering (missense) and loss of function (LoF; nonsense, frameshift, or splice-site) variants from the Exome Aggregation Consortium (ExAC), a large population-based repository of exome sequence data from diverse ancestries that has screened out severe pediatric disease, to assess the overall mutation spectrum of predicted protein-damaging variants across these two genes in the general population. We then determined whether clinically-identified, presumably pathogenic variants implicated in HME exist among healthy individuals. We found six EXT1 and four EXT2 missense mutations in ExAC, suggesting that these mutations have either been misclassified as pathogenic or are not fully penetrant. Furthermore, EXT1 is heavily selectively constrained, while EXT2 is more tolerant to protein-damaging variants, especially at its C-terminus, possibly explaining the genotype-phenotype correlation that EXT1 variants usually result in more severe disease. In conclusion, population-based exome data is a useful filter for determining whether clinically detected variants are likely pathogenic, as well as revealing biological insight into rare disease genes such as EXT1 and EXT2.

Gradual ulnar lengthening in children with multiple exostoses and radial head dislocation: results at skeletal maturity

PURPOSE

Deformities of the forearm and shortening of the ulna occur in 30 % of patients with hereditary multiple exostoses (HME), leading to radial head dislocation and loss of movement. Several surgical techniques have been described for treatment, and the aim of our study was to present clinical and radiographic results at skeletal maturity in 15 children that underwent the surgical procedure of ulnar lengthening with external fixators.

METHODS

We evaluated 15 patients with ulnar shortening and radial head dislocation that underwent external fixation procedures. Radiographic assessment included measurement of radial articular angle, carpal slip, and ulnar shortening. Clinical evaluation included range of motion, MAYO Elbow Score, assessment function of the extremity as described by Stanton, the visual analog scale (VAS) for pain, and SF-12 to evaluate quality of life.

RESULTS

The average follow-up period was 77 months and took place when each patient had reached skeletal maturity. MAYO Elbow Score improved from 34.7 to 93.3 points, while the average preoperative functional assessment criteria score was 1.6 points and improved to 4.4. The preoperative average VAS ranged from 8.2 to 2.3, while the SF-12 in its physical (PCS) and mental (MCS) components resulted, respectively, as 53.3 and 54.2. Pronation and supination improved from a preoperative average value of 35.6° and 51.3° to 70° and 80.6°, respectively, at the most recent follow-up visit. Flexion and extension ranged, respectively, from 143° and 2° to 146.7° and 3°. Ulnar shortening improved from 24 mm preoperative to 3 mm, and radial articular angle varied from 37.7° preoperative to 26° at the last follow-up. Only one complication occurred in our group, and one patient completely healed from a case of nonunion of the ulna.

CONCLUSIONS

Ulnar lengthening is a safe and reliable procedure for the treatment of HME that provides good to excellent results and reduces radial head dislocation.

Multidetector computed tomography in the evaluation of hereditary multiple exostoses

Hereditary multiple exostoses (HME) is an autosomal dominant disorder characterized by the formation of multiple osteochondromas. Because of its superior soft tissue contrast and absence of ionizing radiation, magnetic resonance imaging is the first choice imaging technique for the evaluation of complex lesions and complications related to HME. However, multidetector computed tomography (MDCT) also can be of value in the evaluation of patients with HME, which is reviewed in this article. Topics outlined are low-dose MDCT technique, 3-dimensional visualization techniques, typical MDCT appearances, differential diagnostic considerations, and the usefulness of MDCT in the assessment of emergent and non-emergent complications related to HME, among which spinal cord compression, pneumothorax and hematothorax, pseudoaneurysms, fractures, growth disturbances, chondrosarcoma transformation, and muscular and peripheral nerve involvement.

Cervical myelopathy caused by disc herniation at the segment of existing osteochondroma in a patient with hereditary multiple exostoses

Hereditary multiple exostoses (HME) is a benign hereditary disorder characterized by multiple osteochondromas. Osteochondroma appears occasionally in the spinal column as a part of HME. A 37-year-old man presented with a history of HME and cervical compressive myelopathy caused by intraspinal osteochondroma arising from the lamina of the C5 and disc herniation at the C5-6. He was treated by open-door laminoplasty at the C5 and C6 with excision of the tumor. The neurological symptoms were immediately relieved after surgery. Magnetic resonance images demonstrated a sufficient decompression of the spinal cord with a spontaneous regression of the herniated disc at one year after surgery. There was no recurrence of the tumor and no appearance of kyphosis and segmental instability of the cervical spine on postoperative imaging studies for three years after surgery. The patient could be successfully treated by laminoplasty with excision of the tumor and without removal of the herniated disc.

Hereditary multiple exostoses: anatomical distribution and burden of exostoses is dependent upon genotype and gender

BACKGROUND AND AIMS

We describe the novel anatomical distribution of exostoses in patients with hereditary multiple exostoses according to their gender and genotype.

METHODS AND RESULTS

A prospective database of 143 patients from 65 families with hereditary multiple exostoses was compiled. Patient demographics, genotype and number of exostoses according to anatomical site were recorded. The hand was affected by the greatest proportion of exostoses for both EXT1 (19%) and EXT2 (14%) genotypes and was the most prevalent site for exostoses in patients with an EXT1 genotype (92%). Patients with an EXT1 genotype had a significantly greater number of exostoses compared to those with an EXT2 genotype (2680 vs. 1828, p = 0.006); however, this was only significantly different for 10 of the 19 anatomical regions examined. Male patients with an EXT1 genotype had a significantly (p < 0.05) greater number of exostoses affecting their hands, distal radius, proximal humerus, scapular and ribs compared to female patients with the same genotype and males with an EXT2 genotype.

CONCLUSION

The anatomical distribution of exostoses varies according to genotype and gender; however, the reason for this difference is not clear and may relate to different biochemical pathways.

Can deformity of the knee and longitudinal growth of the leg be predicted in patients with hereditary multiple exostoses? A cross-sectional study

BACKGROUND

There is a high rate of knee deformity in patients with hereditary multiple exostoses (HME), and a quarter of patients have a limb length discrepancy.

METHODS

A prospective database of 172 patients with HME was compiled. Patient demographics, knee deformity and range of movement, leg length and height, and number of exostoses around the knee were recorded.

RESULTS

Nine out of 10 patients with HME were affected by exostoses around the knee, of which the distal femur was the most common site to be involved. Approximately 20% of patients had a valgus deformity and 16% had a fixed flexion deformity of the knee, with 25% having a diminished range of movement. Height was directly proportional to leg length and a quarter of patients were below the 10th centile for height. The presence of a distal femoral exostosis was an independent predictor of knee deformity (p=0.002), diminished range of movement (ROM) (p<0.001), and smaller stature (p<0.001) on multivariate analysis. In addition increasing age, prior surgery, genotype, and gender were also intendant predictors of ROM and height.

CONCLUSION

Future studies analysing if surgical excision improves knee function and limits deformity would need to assess whether this is dependent upon anatomical site, as our results suggest that distal femoral exostoses may have the greatest affect upon these outcomes.

LEVEL OF EVIDENCE

Level II.

Case reports

Hereditary multiple exostosis (HME) is a benign condition with multiple bony tumors with cartilage caps (osteochondromas), mainly presenting in the long and flat bones. Usually the presentation for HME is between 2 and 10 years of age and most are seen by 4 years of age (Khan et al. 2009). In this paper, we report a family with three members (father, son, and a daughter) who had very early presentations of HME in the fingers within the first 2 years of age. The son presented with bony nodules at 7 months of age, and he required surgery at 13 months of age for a severe functional deformity of his left ring finger. He also had an unusual histological presentation on his osteochondroma that consists of only subperiosteal cartilage without ossification.