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PubMed1994

[Familial multiple exostoses].

Case of father and his two sons with multiple osteochondrial exostoses localized on the long bones and impaired joint movements was reported.

Adult↗
PubMed1993

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.

Biomechanical Phenomena↗
PubMed1993

Cervical cord compression in hereditary multiple exostoses.

A seven year old girl, known to have hereditary multiple exostoses, developed moderate gait disorders at the age of six years. Deterioration of myelopathy initiated the clinical investigation including spinal computed tomography (CT) and magnetic resonance imaging (MRI). These examinations demonstrated a coneshaped exostosis originating from the posterior arch of C2. The spinal canal was markedly narrowed with significant compression of the spinal cord at the C2 level. The girl underwent laminectomy of C2 with total removal of the exostosis. Postoperative deterioration of neurological symptoms correlated with a hypointense lesion on T1 weighted imaging in the cord at the same level, but no further cord compression on follow-up MRI. The spastic tetraparesis has improved considerably within 12 months thereafter.

Child↗
PubMed1996

[Positional cloning of the putative gene responsible for transient abnormal myelopoiesis and that for multiple cartilaginous exostoses].

Positional cloning of the putative gene responsible for transient abnormal myelopoiesis (TAM) and that for multiple cartilaginous exostoses (MEX) is described. TAM is a leukemoid reaction occurring frequently in Down syndrome (DS) newborn infants and they often develop true leukemia several years later. The previous findings of "disomic homozygosity in trisomic cells" and tentative mapping of the TAM gene to 21q11.1, and an encounter of a unique DS-associated TAM patient with inv(21) (q11.1q22.13) let us start positional cloning of the TAM gene. One type of MEX is an autosomal dominant disorder and patients with MEX sometimes develop chondrosarcoma. The MEX gene has been mapped to 8q24. We encountered a sporadic case of MEX with de novo t(8q; 13q). Thus, we hypothesized that in both patients, the TAM and the MEX genes are disrupted by the structural chromosome abnormalities. For TAM, we first mapped the proximal breakpoint of inv(21) between 2 STSs using 7 cosmid clones as FISH probes that were isolated on the basis of STS markers at the 21q11.1 region, isolated their corresponding YACs, and then analyzed them. However, since YACs corresponding to 2 other STSs between the two markers could not be isolated, we carried out a chromosome walking to construct a cosmid contig between the 2 STSs. Southern analysis with a cosmid clone within the contig detected EcoRI-/HindIII extra bands on the patient's DNA. The cDNA screening and exon trapping to isolate a gene from the region are underway. Similarly, in the MEX patient we mapped the 8q breakpoint between 2 cosmid markers, then isolated YACs and cosmid subclones. By exon trapping after detection of a cosmid covering the breakpoint, an exon-like sequence was isolated. The 3'-RACE/5'-RACE revealed a novel transcript from this cosmid. Whether the transcript is the MEX gene remains to be determined.

Chromosome Mapping↗
PubMed1997

Hereditary multiple exostoses (EXT): mutational studies of familial EXT1 cases and EXT-associated malignancies.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of cartilage-capped prominences that develop from the growth centers of the long bones. EXT is genetically heterogeneous, with three loci, currently identified on chromosomes 8q24.1, 11p13, and 19q. The EXT1 gene, located on chromosome 8q24.1, has been cloned and is encoded by a 3.4-kb cDNA. Five mutations in the EXT1 gene have been identified--four germ-line mutations, including two unrelated families with the same mutation, and one somatic mutation in a patient with chondrosarcoma. Four of the mutations identified resulted in frameshifts and premature termination codons, while the fifth mutation resulted in a substitution of leucine for arginine. Loss of heterozygosity (LOH) analysis of chondrosarcomas and chondroblastomas revealed multiple LOH events at loci on chromosomes 3q, 8q, 10q, and 19q. One sporadic chondrosarcoma demonstrated LOH for EXT1 and EXT3, while a second underwent LOH for EXT2 and chromosome 10. A third chondrosarcoma underwent LOH for EXT1 and chromosome 3q. These results agree with previous findings that mutations at EXT1 and multiple genetic events that include LOH at other loci may be required for the development of chondrosarcoma.

Bone Neoplasms↗
PubMed1998

[Localization of the gene for 4 hereditary multiple exostoses families].

We investigated 11 families with hereditary multiple exostoses (EXT) by linkage analysis using 8 short-tandem-repeat (CA)n polymorphic markers on chromosomes 8, 11 and 19. The Lod score in four families indicated that the gene responsible for EXT is located in the pericentromeric region of chromosome 11.

Chromosome Mapping↗
PubMed1996

Sutural exostoses, rib hyperostoses, craniosynostosis, mental retardation with focal fat deposition: Proteus syndrome?

We report on a 3-year-old boy with cartilaginous exostoses of the cranial sutures, rib hyperostosis, macrocephaly, metopic craniostenosis, epibulbar dermoid, hyperpigmented macules on the neck, focal fat deposition, and mild mental retardation with marked speech delay. Several of these manifestations were reported previously as an "unknown" by Thanos et al. [1977], with additional clinical information and a diagnosis of Proteus syndrome [Cohen, 1993].

Adipose Tissue↗
PubMed1994

Loss of chromosome band 8q24 in sporadic osteocartilaginous exostoses.

We have karyotyped eight sporadic osteocartilaginous exostoses (OCE), a tumor type not characterized cytogenetically before. Five tumors had only normal karyotypes, whereas three displayed the following abnormal karyotypes: 46,XY,del(8)(q24.1); 46,XX,del(8)(q22), t(8;14)(q24.1;q32); and 46,XY,der(8)t(1;8)(q21;q24),inv(12)(p11q13). All three aberrant cases thus had structural rearrangements leading to loss of the distal part of 8q. This is of particular interest because multiple OCE are part of the disease phenotype in patients with the autosomal dominant tricho-rhino-phalangeal syndrome type II (TRP II), many of whom have constitutional loss of genetic material from 8q24.1. We hypothesis that band 8q24.1 harbors a tumor suppressor gene, the homozygous inactivation of which is important in the genesis of both inherited and sporadic OCE. In the familial form, i.e., in TRP II, loss or functional inactivation of one allele is inherited and only the second mutation is due to a somatic event, whereas both mutations are somatic in the sporadic forms. This hypothesis can be tested by analysis of sporadic and inherited OCE for homozygous loss of 8q24 material with molecular genetic techniques.

Adolescent↗
PubMed1995

A 4-megabase YAC contig that spans the Langer-Giedion syndrome region on human chromosome 8q24.1: use in refining the location of the trichorhinophalangeal syndrome and multiple exostoses genes (TRPS1 and EXT1).

We have constructed a physical map covering over 4 Mb of human chromosome 8q24.1 and used this map to refine the locations of the genes responsible for Langer-Giedion syndrome. The map is composed of overlapping YAC clones that were identified and ordered in relation to sequence tagged sites mapped to the Langer-Giedion chromosomal region on somatic cell hybrids. The minimal region of overlap of Langer-Giedion syndrome deletions, previously identified by analysis of 15 patients, was placed on the map by analysis of 2 patients whose deletions define the endpoints. The chromosome 8 breakpoint of a balanced t(8;9)(q24.11;q33.3) translocation from a patient with trichorhinophalangeal syndrome (TRPS I) was found to be located just within the proximal end of the minimal deletion region. A deletion of 8q24.11-q24.3 in a patient with multiple exostoses was found to overlap the distal end of the LGS deletion region, indicating that the EXT1 gene is distal to the TRPS1 gene and supporting the hypothesis that Langer-Giedion syndrome is due to loss of functional copies of both the TRPS1 and the EXT1 genes.

Animals↗
PubMed2000

Exostoses and cavernous venous formation in the external auditory canal of the hooded seal as a functional physiological organ.

Exostoses of the external auditory canal (EAC) develop after protracted mechanical, chemical or thermal irritation in particular. This is a common disorder among aquatic sportsmen and has been considered unique to Man. We dissected and photodocumented the EACs of 5 newborn and 3 adult Hooded Seals (Cystophora cristata). Serial sections of the EACs were prepared for light microscopic evaluation after staining with haematoxylin-eosin or toluidine blue. All EACs exhibited a firm, broad-based. mountain peak-shaped exostosis on the floor of the meatus, lateral to the eardrum. In addition, the meatal skin of the bony EAC harboured large venous sinuses. The exostosis and venous sinuses of the seal EAC participate in the protection of the sensitive hearing apparatus, particularly the pars tensa portion of the drum, during divine.

Animals↗
PubMed1997

The structure of the human multiple exostoses 2 gene and characterization of homologs in mouse and Caenorhabditis elegans.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by multiple cartilage-capped outgrowths from the epiphyses of long bones. In some cases, these osteochondromas progress to malignant chondrosarcomas. Alterations in at least three genes (EXT1, EXT2, and EXT3) can cause this disorder. Two of these have been isolated (EXT1 and EXT2) and encode related members of a putative tumor suppressor family. We report here the genomic structure of the human EXT2 gene consisting of 14 exons (plus 2 alternative exons) covering an estimated 108 kb of chromosome 11p11-13. We have derived the DNA sequences at all exon/intron boundaries throughout this gene-information that is important for the detailed study of mutations in EXT2. We have also characterized the mouse EXT2 cDNA and have mapped the mouse locus to chromosome 2 between D2Mit15 and Pax6. This mouse homolog should enable transgenic knockout experiments to be initiated to further elucidate gene function. Interestingly, sequence comparisons reveal that the human and mouse EXT genes have at least two homologs in the invertebrate Caenorhabditis elegans, indicating that they do not function exclusively as regulators of bone growth. This observation opens the way for a functional analysis of these genes in nematodes and other lower organisms.

Amino Acid Sequence↗