Exostosis múltiple hereditaria / Hereditary multiple exostoses

Introducción: la exostosis múltiple hereditaria u osteocondromatosis hereditaria es una enfermedad poco frecuente, de transmisión autosómica dominante. Se caracteriza por el crecimiento anómalo, especialmente en las metáfisis de los huesos largos, de osteocondromas benignos que pueden provocar acortamiento o deformidades óseas. Suele diagnosticarse en la primera década de vida.Objetivo: presentar un caso con exostosis múltiple hereditaria, de reporte infrecuente en la literatura, como hallazgo identificado por los médicos colaboradores cubanos en la República de Ecuador.Presentación del caso: escolar masculino de seis años de edad. Acudió a consulta, acompañado de su madre, por presentar un bulto en la mano derecha, con aumento progresivo de tamaño, doloroso y que le impide escribir. En el examen físico se comprobó la deformidad en la extremidad superior derecha, con aumento de volumen en la muñeca de consistencia pétrea que desplazaba la arteria radial. En la tomografía axial computarizada se observó proyección exostósica del tercio distal del radio y se confirmó el diagnóstico.Discusión: las deformidades del antebrazo inducidas por la enfermedad se pueden corregir quirúrgicamente con éxito. La posible recurrencia durante la etapa de crecimiento del niño hace aconsejable esperar hasta la proximidad de la madurez esquelética para realizar los procedimientos correctivos del antebrazo. Conclusiones: las posibles complicaciones óseas, los trastornos neurológicos y vasculares asociados y el riesgo de malignización son características a tener en cuenta por la comunidad médica por la importancia de su diagnóstico temprano con la corrección oportuna de las deformidades óseas que provoca(AU)

Introduction: hereditary multiple exostoses or hereditary osteochondromatosis is a rare disease with autosomal dominant transmission. It is characterized by abnormal growth, especially in the metaphysis of long bones, of benign osteochondromas that can cause shortening or bone deformities. It is usually diagnosed in the first decade of life.Objective: to present a case with hereditary multiple exostoses, of infrequent report in the literature, as a finding identified by the Cuban collaborating doctors in the Republic of Ecuador.Case presentation: male schoolchild of six years of age. He went to consultation, accompanied by his mother, for presenting a lump in his right hand, with a progressive increase in size, painful and that prevents him from writing. In the physical examination, the deformity in the right upper extremity was confirmed, with an increase in the volume of the wrist with a stony consistency that displaced the radial artery. In the computerized axial tomography, an exostoses projection of the distal third of the radius was observed and the diagnosis was confirmed.Discussion: forearm deformities induced by the disease can be successfully corrected surgically. The possible recurrence during the growth stage of the child makes it advisable to wait until the proximity of the skeletal maturity to carry out the corrective procedures of the forearm.Conclusions: possible bone complications, associated neurological and vascular disorders and the risk of malignancy are characteristics to be taken into account by the medical community because of the importance of early diagnosis with the timely correction of bone deformities that it causes(AU)

Transpedicular Excision of a Thoracic Intraspinal Osteochondroma in a Patient with Hereditary Multiple Exostoses and Brown-Séquard Syndrome.

BACKGROUND: Spinal osteochondroma is a rare but recognized cause of myelopathy. Brown-Séquard syndrome is a form of severe myelopathy characterized by a clinical picture of hemisection of the spinal cord. Brown-Séquard syndrome caused by osteochondroma is extremely rare, calling for individualized surgical procedures. CASE DESCRIPTION: We report a 16-year-old girl with hereditary multiple exostoses and a rare case of thoracic osteochondroma causing partial Brown-Séquard syndrome. Customized surgical procedures were designed to avoid iatrogenic spinal cord injury. The patient underwent neural decompression and tumor excision through a transpedicular approach. The surgical procedure consisted of 4 consecutive steps: 1) laminectomy, 2) costotransversectomy and pediculectomy, 3) extracavitary removal of the mass, and 4) pedicular fixation with fusion. Total resection of the tumor was achieved macroscopically without intraoperative spinal cord injury. The postoperative recovery was uneventful, and the patient returned to a normal life without evidence of recurrence at 24-month follow-up. CONCLUSIONS: For patients with hereditary multiple exostosis and new onset of neurologic symptoms, the possibility of a spinal osteochondroma should be considered. In the situation of an intraspinal exostosis protruding from the lateral side, customized surgical procedures with a transpedicular approach may be a valid way to minimize intraoperative neural injury and achieve a satisfactory outcome.

Stüve-Wiedemann syndrome: LIFR and associated cytokines in clinical course and etiology.

Stüve-Wiedemann syndrome (STWS; OMIM #610559) is a rare bent-bone dysplasia that includes radiologic bone anomalies, respiratory distress, feeding difficulties, and hyperthermic episodes. STWS usually results in infant mortality, yet some STWS patients survive into and, in some cases, beyond adolescence. STWS is caused by a mutation in the leukemia inhibitory factor receptor (LIFR) gene, which is inherited in an autosomally recessive pattern. Most LIFR mutations resulting in STWS are null mutations which cause instability of the mRNA and prevent the formation of LIFR, impairing the signaling pathway. LIFR signaling usually follows the JAK/STAT3 pathway, and is initiated by several interleukin-6-type cytokines. STWS is managed on a symptomatic basis since there is no treatment currently available.

A mouse model of chondrocyte-specific somatic mutation reveals a role for Ext1 loss of heterozygosity in multiple hereditary exostoses.

Multiple hereditary exostoses (MHE) is one of the most common skeletal dysplasias, exhibiting the formation of multiple cartilage-capped bony protrusions (osteochondroma) and characteristic bone deformities. Individuals with MHE carry heterozygous loss-of-function mutations in Ext1 or Ext2, genes which together encode an enzyme essential for heparan sulfate synthesis. Despite the identification of causative genes, the pathogenesis of MHE remains unclear, especially with regard to whether osteochondroma results from loss of heterozygosity of the Ext genes. Hampering elucidation of the pathogenic mechanism of MHE, both Ext1(+/-) and Ext2(+/-) heterozygous mutant mice, which mimic the genetic status of human MHE, are highly resistant to osteochondroma formation, especially in long bones. To address these issues, we created a mouse model in which Ext1 is stochastically inactivated in a chondrocyte-specific manner. We show that these mice develop multiple osteochondromas and characteristic bone deformities in a pattern and a frequency that are almost identical to those of human MHE, suggesting a role for Ext1 LOH in MHE. Surprisingly, however, genotyping and fate mapping analyses reveal that chondrocytes constituting osteochondromas are mixtures of mutant and wild-type cells. Moreover, osteochondromas do not possess many typical neoplastic properties. Together, our results suggest that inactivation of Ext1 in a small fraction of chondrocytes is sufficient for the development of osteochondromas and other skeletal defects associated with MHE. Because the observed osteochondromas in our mouse model do not arise from clonal growth of chondrocytes, they cannot be considered true neoplasms.

A mouse model of osteochondromagenesis from clonal inactivation of Ext1 in chondrocytes.

We report a mouse model of multiple osteochondromas (MO), an autosomal dominant disease in humans, also known as multiple hereditary exostoses (MHE or HME) and characterized by the formation of cartilage-capped osseous growths projecting from the metaphyses of endochondral bones. The pathogenesis of these osteochondromas has remained unclear. Mice heterozygous for Ext1 or Ext2, modeling the human genotypes that cause MO, occasionally develop solitary osteochondroma-like structures on ribs [Lin et al. (2000) Dev Biol 224(2):299-311; Stickens et al. (2005) Development 132(22):5055-5068]. Rather than model the germ-line genotype, we modeled the chimeric tissue genotype of somatic loss of heterozygosity (LOH), by conditionally inactivating Ext1 via head-to-head loxP sites and temporally controlled Cre-recombinase in chondrocytes. These mice faithfully recapitulate the human phenotype of multiple metaphyseal osteochondromas. We also confirm homozygous disruption of Ext1 in osteochondroma chondrocytes and their origin in proliferating physeal chondrocytes. These results explain prior modeling failures with the necessity for somatic LOH in a developmentally regulated cell type.

Multiple exostosis: a short study of abnormalities near the growth plate.

The pathogenesis of multiple exostosis has been controversial with many theories put forward including the structural/mechanical theory, which emphasizes that the osteochondroma arises in the displaced growth plate cartilage penetrating a defective periosteum. Recently, molecular genetics has offered the neoplastic model with tumor suppressor genes implicated in the development and pathogenesis of exostosis. In this study, we demonstrated the spectrum of histological abnormalities in the developing exostosis present on the surface of the bone at the physis. Seven skeletally immature patients with multiple exostoses were used in this study. The patients' families were advised of and consented to the proposed study. Coincident with removal of symptomatic exostoses that was adjacent to the physis, a thin strip of bone with overlying periosteum was removed to include the edge of the physis. This was followed by formalin fixation and routine paraffin embedding. We demonstrated the earliest lesion as a microchondroma within the periosteum adjacent to the normal physis (also called the 'groove of Ranvier'). More mature progressively larger lesions showing enchondral ossification were seen distally. The periosteum and the perichondrium were intact with normal physis. Our observations give support to the fact that precursor cells in the periosteum adjacent to the physis (also called the 'groove of Ranvier') gives rise to the chondrocytes that clonally expands and develops into exostosis.

Shortening and deformity of radius and ulna in children: correction of axis and length by callus distraction.

Forearm deformities in children and adolescents may be congenital or developmental, or result from trauma; they may cause pain and decreased function of the wrist and hand. In this study we treated seven patients with forearm deformities (10 forearms) by callus distraction of either the radius or ulna using a monolateral external fixator after osteotomy. Target length was achieved in all cases. The results show significant improvement in range of motion of the forearm. All patients were satisfied with the appearance. There were no complications such as pin tract infection or neural impairment. In one case delayed ossification was resolved by alternating distraction and compression. The timing of correction depends on the implications of the deformity for the carpal bones and the function of the other forearm. Monolateral external fixation proved a versatile tool for correction of forearm deformity in children and adolescents, with a low complication rate.

Disorders of post-squalene cholesterol biosynthesis leading to human dysmorphogenesis.

Insights in molecular developmental biology in animals and humans are facilitating the understanding of pathophysiologic mechanisms in dysmorphogenesis or abnormalities in normal embryologic structural development. A milestone was recognition of the role of shh in morphogenesis of craniofacial structures, especially the development of holoprosencephaly. The dependence of hedgehog morphogens on cholesterol modification for normal hedgehog signaling function has particular relevance to disorders of cholesterol synthesis which manifest dysmorphogenesis. Four human disorders of morphogenesis (Smith-Lemli-Opitz syndrome, desmosterolosis, X-linked chondrodysplasia punctata, CHILD syndrome) have recently been shown to be caused by sterol abnormalities resulting from cholesterol biosynthesis enzyme deficiencies. This review summarizes the clinical, biochemical and molecular data in these disorders with an emphasis on understanding the pathophysiology of dysmorphogenesis.

Herpes simplex virus: discovering the link between heparan sulphate and hereditary bone tumours.

To gain entry into the host, viruses use host cell surface molecules that normally serve as receptors for other ligands. Herpes simplex virus type 1 (HSV-1) uses heparan sulphate (HS) glycosaminoglycans (GAGs) as receptors for initial attachment to the host cell surface. HS GAGs are both ubiquitous and structurally diverse, and normally serve as critical mediators of interactions between the cell and the extracellular environment. We have used the HS binding ability of HSV-1 to identify the function of a cellular gene, EXT1, which is involved in HS polymerisation. Cellular factors that affect virus growth and replication are often key regulators of the cell cycle and EXT1 is no different-humans with inherited mutations in EXT1 have developmental defects that lead to bone tumours (hereditary multiple exostoses, HME) and sometimes chondrosarcomas. Thus, as a result of using HSV-1 as a molecular probe, a functionally orphaned disease gene now has a defined function. These findings highlight the utility of viruses for investigating important cellular processes.

The gradual correction of forearm deformities in multiple hereditary exostoses.

Careful preoperative planning, fixator selection and design, surgical technique, and sustained follow-up care are essential for successful gradual correction of pediatric forearm deformities. The sequence of planning gradual deformity correction can be created by establishing a problem list and using this as the basis for design of the gradual correction. Viewing limb length and deformity correction as a "process," rather than a procedure, is of value. Using a hybrid fixation formula that combines half pins with wires can minimize the potential for neurovascular injury. The combination of radial osteotomy, excision of osteochondromas, and gradual ulnar lengthening by distraction osteogenesis improves forearm appearance and function in most patients with multiple hereditary exostoses.

[Ectopic bone formation: prevention, diagnosis and treatment]. / Ectopische botvorming: preventie, diagnostiek en behandeling.

Two patients are described who developed heterotopic ossification after a minor trauma. The clinical symptoms, pathophysiology and treatment are discussed. We conclude that disabilities and handicaps will be limited by rehabilitation, which includes training of still available functions, and compensation for the lost functions by offering adaptive equipment and adjusting the circumstances. The treatment of patients with heterotopic ossification requires a multidisciplinary approach.

Post-traumatic heel deformity.

The authors describe an apophyseal injury of the calcaneus in a child that resulted in a compound deformity consisting of three separate exostoses. These deformities were corrected by resection of the plantar exostosis and a closing wedge osteotomy of the body of the calcaneus.

Diffuse exostoses and osteomata of the external auditory canal: a report of 100 operations.

The clinical, surgical, and postoperative findings were reviewed in 84 operations for correction of bony stenosis of the external auditory canal caused by diffuse exostoses. Sixteen operations for removal of a solitary osteoma of the external auditory canal are also included in the review. The solitary osteoma is an uncommon unilateral lesion, attached to the tympanosquamous or tympanomastoid suture line, almost always in the outer half of the ear canal. Removal is indicated in most cases and may be performed through the external meatus under local anesthesia. Diffuse exostoses of the external auditory canal are common bilaterally symmetrical hyperostoses of the tympanic bone, seen predominantly in men who are ocean swimmers. Surgical correction of the bony stenosis is indicated only if the lesion is symptomatic. At the Otologic Medical Group we perform the operation postauricularly, rather than transmeatally, in order to remove the lesion completely and to avoid complications.