Multiple Exostoses Research Articles

Management of extremity arterial pseudoaneurysms associated with osteochondromas.

Arterial pseudoaneurysms associated with osteochondromas are rare and most publications on this topic are case reports. The management of this double entity is not standardized. We wanted to update it. Literature searches on MEDLINE and EMBASE were performed using the keywords "artery pseudoaneurysm" and "osteochondroma". Patient demographics, clinical presentations, diagnostic and therapeutic modalities were reviewed. In sum, 101 cases were analyzed. Overall, young adults represented the majority of the affected population with a masculine preponderancy (86%). Painful swelling (51%) was the most commonly physical finding. Distal femur was the most common site of the osteochondroma (86%). Multiple hereditary exostosis was seldom reported (36%). Diagnostic confirmation was dominated by arteriography (55%). Popliteal artery (77%) was the most commonly injured vessel. The treatment was open surgery with vascular repair and optimal exostectomy. Arterial repair was performed with saphenous vein grafting (40%) or lateral suture (39%). Postoperative courses were often uneventful (97%). Arterial pseudoaneurysms resulted from osteochondromas were dominated by those involving the popliteal artery. The use of arteriography to confirm the diagnosis may be limited to the benefit of non-invasive radiological methods because endovascular treatment is not relevant in the setting of osteochondroma-induced arterial pseudoaneurysm.

Imaging of benign complications of exostoses of the shoulder, pelvic girdles and appendicular skeleton.

Exostoses are the most common benign bone tumors, accounting for 10 to 15% of all bone tumors. They develop at the bone surface by enchondral ossification and stop growing when skeletal maturity has been reached. At first, exostoses are covered by a smooth cartilage cap that progressively ossifies with skeleton maturity. Then they may regress, partly or even completely. Osteochondromas may be solitary or multiple, with the latter associated with hereditary multiple exostoses (HME). Exostoses develop during childhood and become symptomatic during the third decade of life in the case of solitary exostoses, or earlier, in case of HME. They stop growing after puberty, when the epiphyseal plates close. Most exostoses remain asymptomatic. Local complications, usually benign, may occur, such as fractures or mechanical impingements upon nearby structures. In rare cases, sarcomatous degeneration occurs. Most of these complications have been described in case reports. This article describes the imaging features of benign complications of exostoses of the shoulder, pelvic girdles and appendicular.

Correction of ankle valgus by hemiepiphysiodesis using the tension band principle in patients with multiple hereditary exostosis

BackgroundAnkle valgus is a common deformity in patients with multiple hereditary exostoses (MHE) and a potential risk factor for early degenerative arthritis. In children, medial hemiepiphysiodesis of the distal tibia is a relatively simple surgical technique used to correct this deformity. We present here the first results of applying this procedure using the eight-Plate guided growth system (eight-Plate) for growth guidance.MethodsBetween 2006 and 2011 we performed hemiepiphysiodesis of the distal medial tibia in 30 ankles of 18 children with MHE using the eight-Plate. Weight-bearing total leg radiographs were obtained preoperatively, during follow-up and at the time of implant removal or when the distal tibial physis had closed. The lateral distal tibia angle (LDTA) was measured and fibular shortening assessed using the Malhotra classification. To evaluate the effect of hemiepiphysiodesis, we correlated the LDTA with age.ResultsThe mean age at time of surgery was 12.6 (range 9.5–15.0) years, and the mean preoperative LDTA was 76.9° (range 68.5°–83.5°). During follow-up, the implant was removed in 12 extremities and the physis had closed in 18 extremities. The mean LDTA at the time of implant removal or at closure of the physis was 83.6° (range 76.5°–90.0°). Mean correction of LDTA was 6.9° after a mean follow-up period of 22 (range 3–43) months. During follow-up, no changes in the Malhotra classification were found in any of the patients. Correction of the valgus deformity of the ankle was significantly correlated (r = −0.506) (p = 0.004) with age in all patients.ConclusionTemporary medial hemiepiphyseodesis of the distal tibia seems to be an effective strategy for correcting ankle valgus in children with MHE. Timing of the intervention is, however, of importance. Hemiepiphyseodesis alone has no effect on the Malhotra classification.Level of evidenceIV, retrospective review.

Rare Malignancies in Eastern India, Socio-Economic Impact.

The etiology of cancer is multifactorial. Various factors, including physical carcinogens, chemicals and viral carcinogens affect patients with known predisposing factors who subsequently develop malignancies. Here is a retrospective study of 18 patients who developed rare malignancies in clinical situations like xeroderma pigmentosum, tuberous sclerosis, neurofibromatosis, hereditary multiple exostosis, second malignancies due to radiotherapy and chronic irritation. The predisposing factors like chronic infection in leprosy, filariasis, poverty and ignorance leading to the chronicity of the lesion, lack of available health care facilities and socio-cultural background, i.e. consanguinity marriage in some community are responsible for the development of these rare malignancies. They were treated at A.H Regional Cancer Centre, Cuttack, Odisha, which is located at Eastern part of India for various malignancies, between January 1989 and January 2008. Malignancies that developed in patients with the above predisposing factors are being reported here due to their rarity and to highlight the impact of socio cultural background in developing these malignancies. Patients with above clinical situations should be kept under close observation for early detection of malignancy so their chances of survival can be improved. In addition, those oncogenic stimuli that initiated or propagated the malignancies, due to socio-economic factors, should be addressed promptly to prevent their eventual development.

Torus palatinus. Report of two cases

Hyperostosis is defined as a benign neoformation of bone tissue, diffused or localized hypertrophy thereof. In the oral cavity can affect the lingual surface of the mandibular bone (torus mandibularis), the hard palate (torus palatinus) or presented as multiple exostosis [1]. The latin word torus means tumor or circular protrusion and is not considered as a pathological condition, but an anatomical variation. The term torus is introduced by Kupfer and Besselhagen in 1879, and is used to designate the exostosis arising on the midline of the palate and the back and inside of the jaw [2].

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

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

Popliteal artery thrombosis complicating posterior tibial exostosis in a 35-year-old male

Chronic popliteal artery thrombosis complicating tibial exostosis has never been described as far as we know. Here, we report the case of a 35-year-old male patient complaining of intermittent claudication over the previous 4 months, without history of trauma or hereditary multiple exostoses. Clinical examination found no popliteal or distal pulses. The diagnosis was confirmed based on CT angiography showing distinct blockage of the contrast product over an exostosis on the posterior side of the proximal tibia. Treatment consisted of removing the exostosis and then bypassing the popliteal artery with a reversed autogenous venous graft.

Is hip dysplasia a common deformity in skeletally mature patients with hereditary multiple exostoses?

Various deformities appear in hereditary multiple exostoses (HMEs). Deformities around the knee or ankle joints are easy to detect in this disease because such deformities are visible in appearance. However, deformities in the hip joints of skeletally mature patients are not well understood because their tumors are invisible. To understand deformities around the hip joint in HMEs, we investigated 36 hip joints in 19 skeletally mature patients (12 males, 7 females). The mean age at last X-ray imaging investigation was 29.2 years (14.5-66.5 years). We evaluated the lesions of exostoses around the acetabulum and proximal femur, Wiberg's center-edge angle (CEA), neck-shaft angle (NSA), acetabular depth-width ratio (ADR), and Sharp's acetabular angle. No exostoses were present in four hips of three cases. Thirty-one hip joints had exostoses on the medial side of the femoral neck. Exostoses existed on the lateral side of the femoral neck in 16 hips. None of the patients had acetabuluar tumors. One patient experienced pain because of impingement between the acetabular rim and medial tumors of the femoral neck. The increase in NSA, which is an index of proximal femoral deformity, was common with a mean NSA of 147.3°. Two indices of acetabular deformity, Sharp's angle and ADR, were within normal limits with a mean Sharp's angle of 41.3° and mean ADR of 269. The average CEA was 29.9°. Hip dysplasia is not necessarily common in skeletally mature patients with HMEs. To determine the possibility of hip dysplasia in skeletally immature patients with HMEs, ADR may be a useful reference index.

External fixation reconstruction of the residual problems of benign bone tumours.

The mechanical features of and biologic response to using distraction osteogenesis with the circular external fixator are the unique aspects of Ilizarov’s contribution that allows deformity correction and reconstruction of bone defects. We present a retrospective study of 20 patients who suffered from a variety of benign tumours for which external fixators (EF) were used to treat deformity, bone loss, and limb-length discrepancy. A total of 26 bony segments in twenty patients (10 males, 10 females; mean age 17 years; range 7–58 years) were treated with EF for residual problems from the tumour itself (primary treatment) in 8 patients and for complications related to the primary surgery (secondary treatment) in 12 patients. Histological diagnoses were Ollier’s disease (n = 4), Fibrous Dysplasia (n = 5), Congenital multiple exostosis (n = 5), giant cell tumour (n = 2) and one case for chondromyxoid fibroma, desmoid fibroma, chondroma and unicameral bone cyst. Various types of external fixators used to treat these problems. These were Ilizarov, unilateral fixator, multiaxial correction frame (Biomet, Parsippany, NJ), Taylor spatial frame (Memphis, TN) and smart correction multiaxial frame. The mean follow-up time was 69.5 months (range 35–108 months). The mean external fixation time was 159.5 days (range 27–300 days). The mean external fixation index was 67.4 days/cm (12–610) in 26 limbs who underwent distraction osteogenesis. The mean length of distraction was 4.9 cm (range 0.2–14 cm). At final follow-up, all patients had returned to normal activities. Complications were in the form of knee arthrodesis in one patient, pin tract infection in six and residual shortening in eight patients. The use of EF and the principles of distraction osteogenesis, in the management of problems associated with benign bone tumours and related surgery yields successful results especially in young patients. With this approach, the risk for recurrence of shortening and deformity may be minimized with overcorrection or over-lengthening as dictated by preoperative planning.

Surgical hip dislocation according to Ganz for excision of osteochondromas in patients with multiple hereditary exostoses.

We report a prospective cohort study of the midterm results of surgical dislocation of the hip (according to Ganz) to perform resection of osteochondromas involving the femoral neck in patients with multiple hereditary exostoses (MHE). Hip range of movement (ROM) was assessed pre- and post-operatively. Patients' judgment of post-operative reduction of pain, symptoms, the Rand 36-item Health Survey (RAND-36) and complications were analysed. Symptomatic osteochondromas of the femoral neck were removed in 20 hips (17 patients) between 2007 and 2012. There were nine men and eight women with a mean age at the time of surgery of 29 years (11 to 47). Mean follow-up was 46 months (26 to 73). At latest follow-up, mean ROM was significantly increased in all directions. Post-operatively the pain associated with the lesion was either significantly decreased or non-existent. There was a significant improvement in seven RAND-36 sub-domains. Encountered complications in four patients were pseudoarthrosis of the trochanteric osteotomy, traumatic separation of the trochanteric osteotomy, a pertrochanteric femoral fracture and avasvular necrosis. Histological analysis revealed osteochondromas in all hips. This study confirms the Ganz trochanteric flip osteotomy provided a reliable approach to osteochondromas of the femoral neck that are otherwise difficult to access for surgical resection. The procedure offered significant improvement in the quality of life, although one should be aware of the serious complications can arise despite the relatively safe procedure. When daily function and activities are affected, resection of osteochondromas of the proximal femur according to Ganz is indicated to significantly improve quality of life.

Deletion of exon 8 from the EXT1 gene causes multiple osteochondromas (MO) in a family with three affected members.

Multiple osteochondromas (also called hereditary multiple exostoses) is an autosomal dominant disorder characterized by multiple cartilaginous tumors, which are caused by mutations in the genes for exostosin-1 (EXT1) and exostosin-2 (EXT2). The goal of this study was to elucidate the genetic alterations in a family with three affected members. Isolation of RNA from the patients’ blood followed by reverse transcription and PCR amplification of selected fragments showed that the three patients lack a specific region of 90 bp from their EXT1 mRNA. This region corresponds to the sequence of exon 8 from the EXT1 gene. No splice site mutation was found around exon 8. However, long-range PCR amplification of the region from intron 7 to intron 8 indicated that the three patients contain a deletion of 4318 bp, which includes exon 8 and part of the flanking introns. There is evidence that the deletion was caused by non-homologous end joining because the breakpoints are not located within a repetitive element, but contain multiple copies of the deletion hotspot sequence TGRRKM. Exon 8 encodes part of the active site of the EXT1 enzyme, including the DXD signature of all UDP-sugar glycosyltransferases. It is conceivable that the mutant protein exerts a dominant negative effect on the activity of the EXT glycosyltransferase since it might interact with normal copies of the enzyme to form an inactive hetero-oligomeric complex. We suggest that sequencing of RNA might be superior to exome sequencing to detect short deletions of a single exon.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-1695-6) contains supplementary material, which is available to authorized users.

Giant osteochondroma of the C5 lamina in a young male

This 21-year-old male presented with history of painless swelling on the left side of the neck for 4 years. There were no neurologic deficits. Local examination showed an 8×9 cm hard bony swelling on the left side of the neck. X-ray imaging showed expansile mass arising from the C5 lamina (Fig. 1A). Computed tomography showed a lobulated expansile mass arising from the left lamina and transverse process of the C5 vertebra (Fig. 1B–D). The magnetic resonance imaging done showed a large bony outgrowth from the left transverse process of C5, with predominantly hyperintense signal on T2weighted images, and hyperto hypointense signal on T1-weighted images. There was no extension of mass into the spinal canal. The vertebral bodies, intervertebral disc spaces, and spinal cord showed normal signal characteristics (Fig. 2A–D). Complete excision of the mass lesion was done. Bony lesion was seen in the posterior triangle of the neck arising from the lamina of C5. Postoperative period was uneventful. Histopathology examination showed vascularized fibrocollagenous tissue features consistent with osteochondroma. The patient was doing well at follow-up of 2 years. Osteochondromas are osseous benign tumors that frequently occur in the long bones especially in metaphysealdiaphyseal parts [1], and are more commonly present in solitary form, although they are multiple in case of hereditary multiple exostoses [2]. These tumors uncommonly occur in the spine [1,3,4]. Patients present with complaints of pain, local swelling, and neurologic deficits, or they may be asymptomatic

Can Multiple Hereditary Exostoses Overlap With Mesomelic Dysplasia?

BackgroundWe studied an unusual combination of severe short stature, mesomelia (Leri-Weill dyschondrosteosis syndrome), and multiple exostosis in several family subjects over three generations. The pattern of inheritance was compatible with autosomal dominant.MethodsOf 21 affected members over three generations, shortness of stature, associated with mesomelia resembling Leri-Weill dyschondrosteosis syndrome with no exostoses was evident in three family subjects. The rest of the family subjects manifested with normal height, and yet multiple exostoses. In this family, the skeletal manifestations were sufficiently variable for the presentation to be with either short stature or scoliosis, a Madelung’ deformity, or with severe hallux valgus associated with exostosis and with Leri-Weill dyschondrosteosis syndrome.ResultsSubjects with structural chromosomal aberrations of the proband IV-7, who manifested with normal height but with multiple exostoses were excluded via 20 CAG-banded mitoses (there were no microdeletions or microduplication after performing Array-CGH-analysis). In addition, DNA examination for subject IV-8 (male cousin of the proband showed short stature and Leri-Weill dyschondrosteosis syndrome) revealed no evidence of SHOX deletions.ConclusionWe described a multigenerational non-consanguineous North African family , in which mesomelic dysplasia, whose clinical and radiological phenotypes resembled dyschondrosteosis, was a prominent feature in three family subjects. Multiple exostoses were evident in several other family subjects (most were with normal height). We would like to emphasize the variability in the phenotypic expression of multiple exostosis, especially the confusion that might arise when the condition appears both clinically and radiologically to be more complicated, and the overall picture might then be overlapped with one of the other bone dysplasias such as Leri-Weill dyschondrosteosis syndrome.

Radiographic Outcomes of Hemiepiphyseal Stapling for Distal Radius Deformity Due to Multiple Hereditary Exostoses.

Multiple hereditary exostoses (MHE) affect the distal forearm in 30% to 60% of patients with this condition. Many surgical interventions have been described, but treatment is controversial. We present the radiographic results of low risk, minimally invasive hemiepiphyseal stapling of the distal radius to correct the joint angulation caused by MHE through growth modulation. A retrospective review was performed on 18 forearms affected by MHE that underwent radial hemiepiphyseal stapling with follow-up of ≥2 years. The radial articular angle, carpal slip, ulnar tilt, lunate subsidence, and metaphyseal epiphyseal angle were measured on preoperative and final postoperative radiographs and compared. Statistically significant (P<0.05) improvements were found in 4 of 5 measurements, including the radial articular angle, carpal slip, ulnar tilt, and metaphyseal epiphyseal angle. No statistical difference was found in lunate subsidence (P=0.84). Hemiepiphyseal stapling of the radial side of the distal radius is a simple and effective method for correcting the radiographic deformity of the distal radius and may be an attractive option for the treatment of the distal radial deformity that is characteristic of the disease. Level IV—therapeutic case series.

Total Hip Arthroplasty Using a Polished Tapered Cemented Stem in Hereditary Multiple Exostosis

A 61-year-old Japanese man underwent right total hip arthroplasty for hereditary multiple exostosis. At first presentation, he had suffered from coxalgia for a long time. On radiographic images, there was a gigantic femoral head, increased shaft angle, and large diameter of the femoral neck. He had also developed coxarthrosis and severe pain of the hip joint. The transformation of the proximal femur bone causes difficulty in setting a cementless total hip prosthesis. Therefore, total hip arthroplasty using a cemented polished tapered stem was performed via a direct lateral approach. Using a cemented polished tapered stem allowed us to deal with the femoral bone transformation and bone substance defectiveness due to exostosis and also minimized the invasiveness of the operation.

Annular pancreas in Trichorhinophalangeal syndrome type II with 8q23.3-q24.12 interstitial deletion

BackgroundTrichorhinophalangeal syndrome type II (TRPS II, OMIM # 150230) is a rare autosomal dominant genetic disorder characterized by craniofacial and skeletal abnormalities. Loss of functional copies of the TRPS1 gene at 8q23.3 and the EXT1 gene at 8q24.11 are considered to be responsible for the syndrome.Case PresentationHerewith, we report an 8-year-old girl with sparse scalp hair, bulbous nose, thin upper lip, broad eyebrows, phalangeal abnormalities of both hands/toes, multiple exostoses, mild intellectual impairment and severe malnutrition. In addition, the patient also had annular pancreas, a rare co-existing feature in patients with TRPS II.ConclusionsA contiguous 5.47 Mb deletion involving 8q23.3-q24.12 was detected by array comparative genomic hybridization (aCGH), leading to haploinsufficiency of 10 protein coding genes, 1 long non-coding RNA and 1 microRNA. Quantitative PCR (qPCR) examination confirmed half-reduced DNA copy of the patient and normal expression of both parents, indicating a de novo origin of the deletion and complete penetrance of the mutation.

Genetic screening of EXT1 and EXT2 in Cypriot families with hereditary multiple osteochondromas.

The purpose of this study was to perform genetic screening of the exostosin 1 (EXT1) and exostosin 2 (EXT2) genes in Cypriot patients with a clinical diagnosis of hereditary multiple osteochondromas (HMO). Initially, mutation analysis of the EXT1 gene was performed by Sanger sequencing. When no point mutation was identified in EXT1, EXT2 analysis was performed. When no sequence variant was identified in either of the candidate genes, array-comparative genomic hybridization (CGH) was implemented to detect any large copy number changes (CNCs). In total, three point mutations and a large deletion were identified in EXT1: the c.2101C>T(p.Arg701*) mutation and the ∼0.16-Mb deletion removing exons 2–11, which were previously reported whereas the c.486_489delCAGA(p.Asp162Glyfs*12) and the c.868G>T(p.Glu290*) mutations which were novel. It is the first report on genetic screening of five HMO patients of Cypriot descent. The observations presented provide additional evidence for the variability in phenotypic expression and the mutational spectrum of this disorder. The term HMO, or hereditary multiple exostoses (HME), MIM: 133700 and MIM: 133701 respectively is used to describe a genetic disorder characterized by the development of multiple, circumscript, occasionally painful and usually symmetric bony protuberances called osteochondromas (benign cartilaginous tumours which most frequently grow outward from the juxtaphyseal region of the long bones or

Identification of a novel frameshift mutation of the EXT2 gene in a family with multiple osteochondroma.

Multiple osteochondroma (MO), also known as multiple hereditary exostoses, is an autosomal dominant skeletal disorder with characteristic multiple cartilage-capped tumours (osteochondromas or exostoses) growing outward from the metaphyseal region of the long tubular bones. Mutations in exostosin glycosyltransferase 1 (EXT1) or EXT2 are the most commonly associated mutations with MO and are responsible for 70–95% of cases. In the present study, a genetic analysis was performed on a large family with MO using polymerase chain reaction and direct DNA sequencing of the entire coding regions of EXT1 and EXT2. Sanger sequencing identified a novel heterozygous frameshift mutation, c.119_120delCT (p.Thr40ArgfsX15), in exon 2 of the EXT2 gene in the proband and all other affected individuals, while this deleterious mutation was not detected in the healthy family members and normal controls. The c.119_120delCT mutation is located in the transmembrane region of the EXT2 protein and results in a truncated EXT2 protein lacking 665 amino acids at the C-terminus, which includes the critical exostosin and glycosyltransferase family 64 domains. Thus, the present study identified a novel causative frameshift mutation in EXT2 from a large MO family. This study is useful for extending the known mutational spectrum of EXT2, for understanding the genetic basis of MO in the patients studied, and for further application of mutation screening in the genetic counseling and subsequent prenatal diagnosis of this family.

Oncology

The October 2015 Oncology Roundup360 looks at: Radiotherapy for the radioresistant; Multiple hereditary exostosis; The total femur as a limb salvage option; Survival prediction in osteosarcoma; What happens when chondrosarcoma recurs?; Thumbs up for vascularised fibular graft; Radiotherapy and survival; Musculoskeletal tumours in pregnancy

HhAntag, a Hedgehog Signaling Antagonist, Suppresses Chondrogenesis and Modulates Canonical and Non-Canonical BMP Signaling.

Chondrogenesis subtends the development of most skeletal elements and involves mesenchymal cell condensations differentiating into growth plate chondrocytes that proliferate, undergo hypertrophy, and are replaced by bone. In the pediatric disorder Hereditary Multiple Exostoses, however, chondrogenesis occurs also at ectopic sites and causes formation of benign cartilaginous tumors--exostoses--near the growth plates. No treatment is currently available to prevent or reverse exostosis formation. Here, we asked whether chondrogenesis could be stopped by targeting the hedgehog pathway, one of its major regulators. Micromass cultures of limb mesenchymal cells were treated with increasing amounts of the hedgehog inhibitor HhAntag or vehicle. The drug effectively blocked chondrogenesis and did so in a dose-dependent manner as monitored by: alcian blue-positive cartilage nodule formation; gene expression of cartilage marker genes; and reporter activity in Gli1-LacZ cell cultures. HhAntag blocked chondrogenesis even when the cultures were co-treated with bone morphogenetic protein 2 (rhBMP-2), a strong pro-chondrogenic factor. Immunoblots showed that HhAntag action included modulation of canonical (pSmad1/5/8) and non-canonical (pp38) BMP signaling. In cultures co-treated with HhAntag plus rhBMP-2, there was a surprising strong up-regulation of pp38 levels. Implantation of rhBMP-2-coated beads near metacarpal elements in cultured forelimb explants induced formation of ectopic cartilage that however, was counteracted by HhAntag co-treatment. Collectively, our data indicate that HhAntag inhibits not only hedgehog signaling, but also modulates canonical and non-canonical BMP signaling and blocks basal and rhBMP2-stimulated chondrogenesis, thus representing a potentially powerful drug-based strategy to counter ectopic cartilage growth or induce its involution.