Multiple hereditary exostoses and enchondromatosis

Pituitary Complications of Enchondromas Due to Maffucci Syndrome

Maffucci syndrome (MS) is a congenital disorder caused by a gain-of-function variant in isocitrate dehydrogenase-1 (IDH1) or isocitrate dehydrogenase-2 (IDH2) genes on chromosomes 2 and 15, respectively. Common manifestations include the development of multiple enchondromas, chondrosarcomas, and intracranial tumors such as pituitary adenomas. Endocrinological conditions are less frequently associated with MS. We present a patient with MS with complete anterior pituitary insufficiency with central hypothyroidism, adrenal insufficiency, and hypogonadotropic hypogonadism, which may be related to the mass effect of her intracranial enchondromas. With hormonal treatments including thyroid hormone replacement, hydrocortisone, and cabergoline, the patient's symptoms of fatigue and cold intolerance improved. We highlight the importance of endocrinological evaluation in patients with neurological tumors related to MS.

Genetic predisposition in sarcomas: clinical implications and management

Recent studies indicate up to 20% of sarcomas may be associated with predisposition genes, and this number will probably increase as genetic testing becomes more available. Evidence on the management of patients with sarcoma and genetic predisposition remains, however, scarce. This review compiles available research on genetic predisposition syndromes associated with sarcoma and sarcoma treatment within such syndromes, addressing key gaps in knowledge. We explore the current evidence on how genetic predisposition may influence treatment decisions and clinical management, focusing on surgery, radiotherapy, systemic treatment, and surveillance. Evidence-based recommendations are currently not available for most syndromes, and we have therefore included pragmatic advice for clinicians. Unanswered questions and unmet needs are also identified, underscoring the importance of multidisciplinary input from specialists such as geneticists, radiologists, surgeons and oncologists. The review stresses the need for future research to improve clinical outcomes for patients with sarcoma and genetic predisposition.

Funding

No funding has been provided for this work.

Identification of novel germline mutations in FUT7 and EXT1 linked with hereditary multiple exostoses

Hereditary multiple exostoses (HME) is an autosomal dominant skeletal disorder primarily linked with mutations in Exostosin-1 (EXT1) and Exostosin-2 (EXT2) genes. However, not all HME cases can be explained by these mutations, and its pathogenic mechanisms are not fully understood. Herein, utilizing whole-exome sequencing and genetic screening with a family trio design, we identify two novel rare mutations co-segregating with HME in a Chinese family, including a nonsense mutation (c.204G>A, p.Trp68*) in EXT1 and a missense mutation (c.893T>G, p.Phe298Cys) in FUT7. Functional assays reveal that the FUT7 mutation affects the cellular localization of FUT7 protein and regulates cell proliferation. Notably, the simultaneous loss of fut7 and ext1 in a zebrafish model results in severe chondrodysplasia, indicating a functional link between FUT7 and EXT1 in chondrocyte regulation. Additionally, we unveil that FUT7 p.Phe298Cys reduces EXT1 expression through IL6/STAT3/SLUG axis at the transcription level and through ubiquitination-related proteasomal degradation at the protein level. Together, our findings not only identify novel germline mutations in FUT7 and EXT1 genes, but also highlight the critical interaction between these genes, suggesting a potential 'second-hit' mechanism over EXT1 mutations in HME pathogenesis. This insight enhances our understanding of the mechanisms underlying HME and opens new avenues for potential therapeutic interventions.

Hereditary Multiple Osteochondromas and Acute Lymphoblastic Leukemia: A Possible Role for EXT1 and EXT2 in Hematopoietic Malignancies

Hereditary multiple osteochondromas (HMO) is an autosomal dominant disorder caused by heterozygous deleterious variants in the EXT1 or EXT2 genes. While the clinical core phenotype is well established and mainly consists of bone deformities, limb length discrepancies, multiple benign bone neoplasms, and increased risk of chondrosarcoma, the association of HMO with malignancies remains undefined. Only two cases have been reported to date. We report a third patient with HMO and leukemia. New research suggests that EXT1 and EXT2 genes may influence leukemogenesis through several mechanisms, including protein-protein interactions with leukemia-associated genes and modulation by specific microRNAs (miRNAs). Dysregulation of heparan sulfate biosynthesis, a pathway involving exostosin proteins, may disrupt the bone marrow microenvironment, impacting hematopoietic cell growth and differentiation.

Deficiency of EXT1 and FGFR3 genes promotes chondrocyte differentiation, leading to the induction of osteochondroma formation

OBJECTIVE

This study aims to investigate the roles of the EXT1 and FGFR3 genes in the development of osteochondromas, focusing specifically on their potential interactions in chondrocyte proliferation, differentiation, and tumor formation.

METHODS

In vitro, the ATDC5 chondroprogenitor cell line was used to examine the effects of inactivation of both EXT1 and FGFR3. In vivo, a mouse model with dual gene knockout of Ext1 and Fgfr3 was constructed to further explore these genes' roles in tumor formation by observing the incidence and distribution patterns of osteochondromas.

RESULTS

The in vitro experiments demonstrated that ATDC5 cells with reduced expression of EXT1 and FGFR3 genes exhibited enhanced chondrogenic differentiation. In vivo, Fgfr3+/-;Ext1+/- mice showed a significant incidence of osteochondromas (72.7 %), primarily located in the humerus, fibula, and tibia, while mice with a single heterozygous deletion did not display notable lesions.

CONCLUSION

The EXT1 and FGFR3 genes play crucial regulatory roles in the development of osteochondromas. Deficiencies in Ext1 and Fgfr3 can induce the formation of osteochondromas.

Hereditary multiple exostoses: an educational review

Hereditary multiple exostoses (HME), an autosomal dominant disorder with an incidence of 1:50,000 to 1:100,000, is characterised by the formation of multiple osteochondromas arising from the metaphyses of long and flat bones. These osteochondromas often present as painless palpable lumps, though some cases are symptomatic due to mechanical compression or bursitis. Diagnosis of HME is typically clinical and radiological. WHO diagnostic criteria include ≥ 2 radiological osteochondromas in the juxta-epiphyseal region of the long bones. Genetic testing is reserved for ambiguous cases. HME is associated with mutations in the EXT-1 (exostosin-1) and EXT-2 (exostosin-2) genes. Imaging techniques, including conventional radiography, CT, MRI, ultrasound, and nuclear medicine, play a crucial role in diagnosing and assessing HME, with each modality offering distinct advantages in visualising the lesions and associated complications. Common complications include skeletal deformities, fractures, bursitis, as well as neural and vascular abnormalities. Notably, there is a 10% risk of malignant transformation into secondary chondrosarcoma in HME patients, compared to only a 1% risk in those with solitary osteochondromas. Malignant transformation should be suspected in patients with new-onset pain or specific imaging features in an osteochondroma, such as growth of de cartilaginous cap. In these cases, an MRI should be performed to assess the cartilage cap thickness. Advances in imaging techniques and genetic understanding have improved the management and prognosis of HME. Follow-up is essential to rule out malignant transformation. This review summarises current knowledge on the clinical presentation, pathogenesis, imaging characteristics, complications, and treatment of HME. CRITICAL RELEVANCE STATEMENT: HME is a disorder characterised by the formation of osteochondromas arising from long and flat bones. Multi-modality imaging characteristics, clinical presentation, complications, and treatment are highlighted to familiarise the readers with this entity and offer optimal patient care. KEY POINTS: HME is characterised by multiple osteochondromas on long and flat bones. Imaging for HME includes radiography, CT, MRI, ultrasound, and nuclear medicine studies. Complications include non-malignant complications, such as bone deformities and malignant transformation. Cartilage-cap measurement with MRI or US is key to exclude malignancy. Follow-up is essential to rule out malignant transformation of the osteochondromas.

Forearm Giant Osteochondromas in a Young Patient With Multiple Hereditary Exostoses: A Case Report

Multiple hereditary exostoses (MHE) is a rare skeletal disorder inherited as an autosomal dominant disorder. It is characterized by widespread multiple osteochondromas that grow near bone growth plates, leading to pain and deformities that significantly impact physical and emotional well-being and disrupt daily activities, social interactions, and psychological health, leading to considerable disability. This case report describes a 15-year-old boy with a family history of MHE who developed a large osteochondroma at his right elbow. We aim to present the surgical management of extraordinarily large-size proximal radius osteochondroma, fortunately, caused by a benign underlying condition despite typically carrying more chances of transformation into malignancy.‎ To the best of our knowledge, it would be the largest proximal radius osteochondroma documented in the literature.

Generation of Ext1 Gene-Edited Mice Model Via Dual sgRNAs/Cas9 System and Phenotypic Analyses

Hereditary multiple exostoses (HME) is an autosomal dominant skeletal disease. Genetic linkage analyses have identified that mutations in the exostosin glycosyltransferase (EXT)1 and EXT2 genes are linked to HME pathogenesis, with EXT1 mutation being the most frequent. The aim of this study was to generate a mice model with Ext1 gene editing to simulate human EXT1 mutation and investigate the genetic pathogenicity of Ext1 through phenotypic analyses. We designed a pair of dual sgRNAs targeting exon 1 of the mice Ext1 gene for precise deletion of a 46 bp DNA fragment, resulting in frameshift mutation of the Ext1 gene. The designed dual sgRNAs and Cas9 proteins were injected into mice zygotes cytoplasm. A total of 14 mice were obtained via embryo transfer, among which two genotypic chimera mice had a deletion of the 46 bp DNA fragment in exon 1 of the Ext1 gene. By hybridization and breeding, we successfully generated heterozygous mice with edited Ext1 gene (Ext+/-). Off-target effect analysis did not reveal off-target mutations in Ext+/- mice caused by the two sgRNAs used. Compared to wild-type mice, Ext+/- mice exhibited lower body weights. X-ray imaging showed hyperplastic bone near caudal vertebrae only in male Ext+/- mice, with computed tomography values approximately at 200 HU for hyperplastic bone between ribs and spine regions. Furthermore, immunohistochemical analysis revealed fewer articular chondrocytes expressing EXT1 in edited mice compared to wild-type ones. Pathological section analysis demonstrated no structural or morphological abnormalities in heart, liver, lung, or kidney tissues from Ext+/- mice. In conclusion, we successfully generated an accurate DNA deletion model for studying Ext1 using dual sgRNAs/Cas9 systems. In conclusion, we successfully generated precise DNA deletions in the Ext1 mice model using the dual sgRNAs/Cas9 system. In conclusion, we observed significant phenotypic changes in Ext+/- mice, particularly bone hyperplasia in male individuals; however, no exostosis was detected in the gene-edited mice. The introduction of a frameshift mutation into the Ext1 gene through CRISPR/Cas9 technology resulted in novel phenotypic alterations, highlighting the genetic pathogenicity of Ext1. Therefore, our Ext+/- mice serve as a valuable model for further biomedical investigations related to the Ext1 gene.

Nature-based interventions for individuals with rare skeletal disorders: evaluation of a 5-day sailing program on health-related quality of life

Individuals with rare skeletal disorders like Multiple Osteochondromas and Ollier Disease often experience physical and psychological burdens. Adventure therapy, with activities like sailing in outdoor settings, promotes personal growth and psychological well-being, potentially improving health-related quality of life (HRQoL). This study aimed to evaluate the impact of a sailing program on health-related quality of life and participant satisfaction in individuals with Multiple Osteochondromas and Ollier Disease. A quasi-experimental one-group pre-post design was employed, with HRQoL assessed using the EQ-5D® instrument and participant satisfaction measured via a feedback survey. Data were collected before and after the five-day sailing program conducted in the Mediterranean Sea in 2022 and 2023, involving participants diagnosed with Multiple Osteochondromas and Ollier Disease. Statistical analyses were performed using the Wilcoxon signed-rank test and McNemar's test for paired data. A significance level of p < 0.05 and p < 0.10 was considered. A total of 25 participants, predominantly male (52%), with a median age of 16 years (ranking from 11 to 31), were included in the study. The sailing program had mixed impact on HRQoL. Specifically, individuals who were female (p = 0.03), aged 16 and older (p = 0.04), with higher educational attainment (p = 0.10) or stronger self-management (p = 0.09), resilience (p = 0.01) and self-engagement (p = 0.09) skills experienced enhanced HRQoL. Conversely, other participants exhibited an increase in self-care difficulties (p = 0.02) and a trend towards worsening pain/discomfort (p = 0.38). Overall satisfaction with the program was high, with 90% of participants expressing satisfaction.This is the first study which examined HRQoL in Multiple Osteochondromas and Ollier Disease patients within an outdoor adventure therapy setting. Findings suggest that adventure therapy, integrated into healthcare strategies, may offer a valuable complement to conventional treatments for rare skeletal disorders. Future research, including randomized controlled trials, are necessary to confirm these results and develop robust interventions for improving the well-being in this population.

Therapeutic effect of intramedullary reaming and nailing for long bones lengthening in children with Ollier disease and Maffucci syndrome on enchondromas: multicentric retrospective case series

INTRODUCTION

Leg length discrepancy (LLD) and malalignment of long bones are frequent orthopedic problems encountered in Maffucci syndrome and Ollier disease (OD). Orthopedic surgeons used historically external fixators to address the deformities. In this multicentric case series, we propose the use of motorized intramedullary nails.

METHODS

We retrospectively reviewed for 9 years, in four different centers, patients with OD and Maffucci's syndrome that had lengthening nails for LLD with or without associated deformities. The minimum follow-up period was 24 months. We reported complications, clinical tolerance of lengthening, lengthening rate and target, bone healing index, and EQ-5D-Y functional and visual analog scores (VAS). We also saw on X-rays the whole lengthened bone and its regenerate zone to assess the evolution of the enchondromas.

RESULTS

we used the nailing technique in 8 femurs and 2 tibias in 8 patients (mean age: 13.3 years, range: 11-16, mean follow-up time: 53.8 months, range: 26-108). The mean correction amount was 6.44 cm for the femur over 76.8 days and 3.75 cm over 44 days for the tibia with a mean VAS score of 6.63/15 and mean EQ-5D-Y of 81/100. The lengthening goal was achieved in all patients. No mechanical complications were noted. The medullary canal of the operated bones showed improvement and healing in 8 out of 10 segments.

DISCUSSION

Besides achieving the goals of surgery with good functional outcomes, lengthening nails has a therapeutic effect on enchondromas with fewer complications than traditional correction methods.

Defining priorities in the transition from paediatric to adult healthcare for rare bone disease patients: a dialogic approach

The Italian patient association for Multiple Osteochondromas, Ollier Disease, and Maffucci Syndrome, Associazione Conto Alla Rovescia-ACAR Aps, conducted a mixed-methods study at its 2023 annual conference. The study included the Open Dialogue Approach and a feedback survey to identify the main priorities in the transitioning process from paediatric to adult healthcare for patients with Multiple Osteochondromas, Ollier Disease, and Maffucci Syndrome. The common needs identified by patients, families, caregivers, and healthcare professionals were coordination and continuity of care, patient empowerment and communication, social and practical support, and transition planning and support. This experience fostered a sense of collaboration and cooperation among stakeholders, helping to build trust and create a shared vision for improving the quality of care for these patients. Furthermore, it could be considered a starting point for other patient associations interested in using different approaches to identify the needs of their members and actively involve all stakeholders.

The Utility of PET/CT for the Diagnosis of Periosteal Chondrosarcoma in a Patient With Maffucci's Syndrome

Maffucci's syndrome is a rare congenital nonhereditary syndrome with less than 300 cases having been reported in the United States. It is characterized by multiple enchondromas, hemangiomas, and rarely lymphangiomas. Enchondromas may undergo malignant transformation to chondrosarcomas. Surveillance plays a vital role in detecting early malignant transformation. Fluorodeoxyglucose (FDG) PET/CT, although falling out of favor, may be utilized as an imaging modality by physicians to determine such transformation, allowing for timely management and intervention. In this report, we share our experience with such a case.

Rib spur causing a hemothorax, pneumothorax, and diaphragmatic injury in a pediatric patient

Pleural effusion is a relatively common condition encountered in the pediatric emergency department. Evaluation of pleural effusion in the emergency department typically includes advanced imaging such as computer tomography or ultrasound, as well as diagnostic thoracocentesis. We report a case of a 10-year-old female with a rib spur at the anterolateral left sixth rib that caused a hemothorax, pneumothorax, and diaphragmatic injury. The patient underwent video-assisted thoracoscopic surgery and resection of the rib spur. The procedure was well-tolerated without any complications.

Anatomical study of a human skull with multiple osteomas in a seventeenth-century Dutch still-life painting: bone morphology and artistic intention

Skulls were frequently depicted in seventeenth-century Dutch still-life paintings. Skulls were interpreted as symbols of vanitas-meaning the evanescence of life-but their morphological features have received little attention. This study analyzed a skull with abnormal tumors in a seventeenth-century Dutch still-life painting by a renowned artist, Edwaert Collier (ca. 1642-1708), from anatomical, forensic, and pathological perspectives. The morphology of the cranium and teeth indicated that the skull likely belonged to a middle-aged female. We carefully diagnosed the abnormal masses as multiple osteomas on the skull and left femur, based on clinical studies and paleopathological literature, which reported lesions with a similar appearance to those observed in Collier's work. Furthermore, detailed observations of the cranial sutures and epiphyses of the long bones in his paintings revealed that the artist may have selected bones with a morphology that was suitable for the subject of vanitas. Collier repeatedly depicted the skull with metopism, the rare condition of having a persistent metopic suture in adulthood. A skull with a metopic suture is called Kreuzschädel, meaning the cross skull, because it forms a cruciform by connecting with the sagittal and coronal sutures. The artist might have chosen skulls with metopic sutures, which is reminiscent of the crucifixion of Christ, as an appropriate motif for the vanitas painting. This paper argues that anatomical analysis could explain the hidden meaning of the painting and disclose the fascinating collaborations between anatomy and art in the seventeenth-century Dutch Republic.

Premalignant Conditions of Bone

Development of malignancy is a multifactorial process, and there are multitude of conditions of bone that may predispose patients to malignancy. Etiologies of malignancy include benign osseous conditions, genetic predisposition, and extrinsic conditions. New-onset pain or growth in a previously stable lesion is that should concern for malignant change and should prompt a diagnostic workup for malignancy.

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.

Update on the imaging features of the enchondromatosis syndromes

Ollier disease and Maffucci syndrome are the commonest enchondromatosis subtypes, arising from non-hereditary mutations in the IDH1 and IDH2 genes, presenting in childhood and being characterised by multiple enchondromas. Maffucci syndrome also includes multiple soft tissue haemangiomas. Aside from developing bony masses, osseous deformity and pathological fracture, ~ 40% of these patients develop secondary central chondrosarcoma, and there is increased risk of non-skeletal malignancies such as gliomas and mesenchymal ovarian tumours. In this review, we outline the molecular genetics, pathology and multimodality imaging features of solitary enchondroma, Ollier disease and Maffucci syndrome, along with their associated skeletal complications, in particular secondary chondrosarcoma. Given the lifelong risk of malignancy, imaging follow-up will also be explored. Metachondromatosis, a rare enchondromatosis subtype characterised by enchondromas and exostoses, will also be briefly outlined.

An Easy-to-Use Approach to Detect CNV From Targeted NGS Data: Identification of a Novel Pathogenic Variant in MO Disease

BACKGROUND

Despite the new next-generation sequencing (NGS) molecular approaches implemented the genetic testing in clinical diagnosis, copy number variation (CNV) detection from NGS data remains difficult mainly in the absence of bioinformatics personnel (not always available among laboratory resources) and when using very small gene panels that do not meet commercial software criteria. Furthermore, not all large deletions/duplications can be detected with the Multiplex Ligation-dependent Probe Amplification (MLPA) technique due to both the limitations of the methodology and no kits available for the most of genes.

AIM

We propose our experience regarding the identification of a novel large deletion in the context of a rare skeletal disease, multiple osteochondromas (MO), using and validating a user-friendly approach based on NGS coverage data, which does not require any dedicated software or specialized personnel.

METHODS

The pipeline uses a simple algorithm comparing the normalized coverage of each amplicon with the mean normalized coverage of the same amplicon in a group of "wild-type" samples representing the baseline. It has been validated on 11 samples, previously analyzed by MLPA, and then applied on 20 patients with MO but negative for the presence of pathogenic variants in EXT1 or EXT2 genes. Sensitivity, specificity, and accuracy were evaluated.

RESULTS

All the 11 known CNVs (exon and multi-exon deletions) have been detected with a sensitivity of 97.5%. A novel EXT2 partial exonic deletion c. (744-122)-?_804+?del -out of the MLPA target regions- has been identified. The variant was confirmed by real-time quantitative Polymerase Chain Reaction (qPCR).

CONCLUSION

In addition to enhancing the variant detection rate in MO molecular diagnosis, this easy-to-use approach for CNV detection can be easily extended to many other diagnostic fields-especially in resource-limited settings or very small gene panels. Notably, it also allows partial-exon deletion detection.

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.

IDH1 R132C and ERC2 L309I Mutations Contribute to the Development of Maffucci's Syndrome

Background

Maffucci's syndrome is characterized by the coexistence of multiple enchondromas and soft-tissue hemangiomas. It has been clear that somatic mosaic isocitrate dehydrogenase type 1 (IDH1) or isocitrate dehydrogenase type 2 (IDH2) mutations are associated with Maffucci's syndrome and Ollier disease, but the mechanisms underlying hemangiomas of the Maffucci's syndrome is still obscure. This study aimed to determine the mechanism of hemangiomas in Maffucci's syndrome.

Methods

We received a 26-year-old female patient with typical Maffucci's syndrome, and exome sequencing was conducted using DNA from her peripheral blood and enchondroma tissues. Somatic mutations were characterized by a comparative analysis of exome sequences and further confirmed by the sequencing of PCR products derived from original blood and tissue samples. The mutations of an additional 69 patients with Ollier disease were further tested. The functional impacts of these somatic mutations on Maffucci's syndrome, especially the development of hemangiomas, were evaluated.

Results

We reported a typical case of Maffucci's syndrome, which was confirmed by both imaging findings and pathology. Through exome sequencing of this patient's DNA samples, we identified an R132C mutation in the isocitrate dehydrogenase type 1 (IDH1) gene and an L309I mutation in the ELKS/RAB6-interacting/CAST family member 2 (ERC2) gene in this patient. Approximately 33.3% of the clones were positive for the IDH1 R132C mutation, and 19.0% of the clones were positive for the ECR2 L309I mutation. The IDH1 R132C mutation was detected in most of the patients with Ollier disease (51/69 patients), and the mean frequency of this mutation was 63.3% in total sequence readouts, but the ECR2 L309I mutation was absent in all of the patients with Ollier disease. In vitro experiments confirmed that the IDH1 R132C mutation promotes chondrocyte proliferation, and the ERC2 L309I mutation enhances angiogenesis.

Conclusions

Our results suggest that while IDH1 is a known pathogenic gene in enchondromatosis, ERC2 is a novel gene identified in Maffucci's syndrome. The somatic L309I mutation of ERC2 contributes to the pathogenesis of hypervascularization to facilitate the development of hemangiomas in Maffucci's syndrome. The combination of the IDH1 R132C and ERC2 L309I mutations contributes to the development of Maffucci's syndrome, and these results may enable further research on the pathogenesis of Maffucci's syndrome.

An update on the imaging of diaphyseal aclasis

Solitary osteochondromas are common, benign hyaline cartilage-capped exostoses that primarily arise from the metaphyses of long and flat bones. Diaphyseal aclasis is an autosomal dominant condition resulting from EXT1 or EXT2 gene mutations and is characterized by multifocal osteochondromas. These can result in a wide spectrum of complications, such as skeletal deformity, neurological and vascular complications, adventitial bursa formation, fracture, and rarely malignant transformation to peripheral chondrosarcoma. In this review, we outline in detail the multimodality imaging features of DA and its associated complications.

The Rizzoli Multiple Osteochondromas Classification revised: describing the phenotype to improve clinical practice

Multiple osteochondromas (MO) is a rare disorder, characterized by benign osteocartilaginous tumors (osteochondromas), arising from the perichondrium of bones. The osteochondromas increase during growth, frequently causing deformities and limitations. Our study aims to analyze the data captured by the Registry of Multiple Osteochondromas, to refine Istituto Ortopedico Rizzoli (IOR) Classification, providing a representative picture of the phenotypic manifestations throughout the lifespan. We conducted a single‐institution cross‐sectional study. Patients were categorized according to IOR Classification, which identifies three patients' classes on the presence/absence of deformities and/or limitations. The present dataset was compared with our previously published data, to refine the classification. Nine hundred sixty‐eight patients were included: 243 children (<10 years), 136 adolescents (10–15 years), and 589 adults. Of the entire population, half patients presented at least one deformity, and one quarter reported at least one limitation. Compared with our previous study, the amount of children was more than doubled and the percentage of mild/moderate cases was notably increased, giving a better disease overview throughout the lifespan and suggesting a different cut‐off for dividing Class II in subclasses. We confirmed that MO is characterized by phenotypic heterogeneity, suggesting that an early classification of the disease may offer a useful tool to follow disease pattern and evolution, to support clinical practice, and to propose timely interventions.

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.

Endoscopic endonasal extreme far-medial approach for a lower clivus osteochondroma in a patient with hereditary multiple exostoses: illustrative case

BACKGROUND

The authors reported on the use of endoscopic endonasal surgery (EES) for clivus osteochondroma in a patient with hereditary multiple exostoses (HME), a rare pediatric disorder characterized by the formation of osteochondromas adjacent to the growth plates of the axial and appendicular skeletal elements.

OBSERVATIONS

A 26-year-old man with a family history of HME reported progressive hoarseness and dysphagia over the previous 6 months. He was referred to us after magnetic resonance imaging (MRI) showed a bone tumor in the lower clivus. MRI revealed tumor proliferation in the lower clivus and its extension to the bilateral occipital condyle and jugular tubercle. The hypoglossal canal and jugular foramen were encased on the right side, whereas the medulla oblongata was compressed. The tumor was subtotally resected with EES, and the brainstem was successfully decompressed. The pathological diagnosis was exostoses. Transient postoperative worsening of dysphagia improved within 1 month without other neurological deficits. The patient underwent posterior occipitoaxial fixation 3 months after EES to correct instability and local lateral tilt of the right atlanto-occipital joint.

LESSONS

The authors’ experience showed that EES is effective for resection of lower clivus osteochondromas, including the cartilaginous cap, and may improve clinical outcomes in patients with HME.