The tricho-rhino-phalangeal syndrome with exostoses (or Langer-Giedion syndrome): four additional patients without mental retardation and review of the literature

Association of Trichorhinophalangeal Syndrome and Loose Anagen Syndrome: A Case Report

Trichorhinophalangeal syndrome (TRPS) is an autosomal dominant disease characterized by trichologic, craniofacial, and musculoskeletal abnormalities. Predominant clinical features include a pear-shaped nose with bulbous tip, long philtrum, protruding ears, and sparse hair on both the scalp and the lateral third of the eyebrows. Cone-shaped epiphyses are a common radiographic finding. Loose anagen syndrome (LAS) is a sporadic or autosomal dominant condition due to abnormalities in the hair's anchoring mechanism. It mostly affects children, who usually have reduced hair length, as well as hair that is easily plucked without pain. Recent contributions regarding trichoscopic findings of LAS have been made, describing rectangular black granular structures as a typical feature. An association between TRPS and LAS has been mentioned by hair experts, but no reports documenting this have been published. This case demonstrates the co-existence of both conditions in a patient with characteristic phenotypic traits of TRPS and LAS.

An intragenic duplication of TRPS1 leading to abnormal transcripts and causing trichorhinophalangeal syndrome type I

Trichorhinophalangeal syndrome type I (TRPSI) is a rare disorder that causes distinctive ectodermal, facial, and skeletal features affecting the hair (tricho-), nose (rhino-), and fingers and toes (phalangeal) and is inherited in an autosomal dominant pattern. TRPSI is caused by loss of function variants in TRPS1, involved in the regulation of chondrocyte and perichondrium development. Pathogenic variants in TRPS1 include missense mutations and deletions with variable breakpoints, with only a single instance of an intragenic duplication reported to date. Here we report an affected individual presenting with a classic TRPSI phenotype who is heterozygous for a de novo intragenic ∼36.3-kbp duplication affecting exons 2–4 of TRPS1. Molecular analysis revealed the duplication to be in direct tandem orientation affecting the splicing of TRPS1. The aberrant transcripts are predicted to produce a truncated TRPS1 missing the nuclear localization signal and the GATA and IKAROS-like zinc-finger domains resulting in functional TRPS1 haploinsufficiency. Our study identifies a novel intragenic tandem duplication of TRPS1 and highlights the importance of molecular characterization of intragenic duplications.

High-functioning autism in a Sri Lankan youth with Langer-Giedion syndrome

The trichorhinophalangeal syndrome is a rare genetic disorder with a classical clinical triad of sparse hair, bulbous nose, and short digits. There are three known phenotypes, and the type II with exostoses in long bones is known as Langer-Giedion syndrome. Here, we describe a 28-year-old Sri Lankan male with Langer-Giedion syndrome and high-functioning autism. The karyotype found a microdeletion of the long arm of chromosome 8 with mosaicism [46,XY/46,XY,del(8)(q24.1q24.3)]. This is probably the first report of Langer-Giedion Syndrome with autism and the first report of the genetic syndrome from Sri Lanka. Furthermore, we could only access one previous report of the same microdeletion, which was from an autopsy of a 36-week-old infant.

Dysmorphic Short Stature: Radiological Diagnosis of Trichorhinophalangeal Syndrome

Trichorhinophalangeal syndrome (TRPS), a type of skeletal dysplasia, is characterized by a triad of dysmorphic (bulbous nose and large ears); ectodermal (thin and sparse hair); and skeletal (short stature and cone-shaped epiphyses) findings, and this combination is helpful for early diagnosis and appropriate follow-up. A 14-year-old boy presented with short stature and distinctive facial features, and following the first clinical and biological evaluation, no precise diagnosis was reached. Progressive bilateral development of noninflammatory and painless deformity of his second finger required a radiological exam that highlighted the key elements (cone-shaped epiphyses) for final diagnosis. This case illustrates the difficulties to early recognition of TRPS when the clinical presentation is not complete and radiological findings are missing.

Multiple long bone cysts revealed by MRI in trichorhinophalangeal syndrome type II predisposing to pathological fractures

Trichorhinophalangeal syndrome type II is a rare genetic disorder with the few published case reports mainly reporting the radiographic skeletal manifestations. There are no published imaging reports of long bone cysts involving multiple bones in this condition. We report a unique case of bone cysts involving multiple long bones detected with MRI in a patient with trichorhinophalangeal syndrome type II complicated by a subsequent pathological fracture. It is possible that the bone cysts are a previously undescribed feature of this syndrome; however, the evidence is insufficient to establish a definite association. Chromosomal abnormality identified in this patient is consistent with trichorhinophalangeal syndrome type II with no unusual features. Although the nature of these bone cysts is unclear, they are one of the causes of the known increased fracture risk observed in this syndrome.

Langer-Giedion syndrome associated with congenital dural arterio-venous fistula

Langer-Giedion syndrome (LGS) is a rare disease caused by deletion of chromosome 8q23.3-q24.11. Clinical manifestations include among others multiple exostoses, short stature, intellectual disability, and typical facial dysmorphism. Dural arterio-venous shunts (DAVS) in the pediatric age are rare lesions, which have been classified into three types: dural sinus malformations (DSM), infantile type DAVS (IDAVS), and adult type DAVS (ADAVS). We report a case of a patient with a known LGS who was diagnosed with complex intracranial dural AV fistula at the age of 20. An association between LGS and intracranial dural AV fistulas has to our knowledge never been reported before.

A novel TRPS1 mutation in a family with tricho-rhino-phalangeal syndrome type 1

Tricho-rhino-phalangeal syndrome (TRPS) is an autosomal-dominant disease characterized by sparse and slow-growing scalp hair and craniofacial and skeletal abnormalities. We report here the case of two girls and their father who had TRPS type 1 and received a diagnosis of a new mutation of TRPS1 based on their clinical symptoms. Moreover, histological studies on skin samples obtained from one of the patients showed enhanced signal transducers and activator of transcription (STAT) 3 expression in the outer root sheath. However, TRPS1 protein expression was not reduced in the patient's follicles. These findings indicate that truncated TRPS1 protein from the mutant allele may be stably expressed in the patient's follicles and that enhanced STAT3 expression may be involved in the development of sparse and thin scalp hair in TRPS.

Skeletal abnormalities of tricho-rhino-phalangeal syndrome type I

The tricho-rhino-phalangeal syndrome (TRPS) type I is a rare genetic disorder related to the TRPS1 gene mutation in chromosome 8, characterized by craniofacial abnormalities and disturbances in formation and maturation of bone matrix. The hallmarks are sparse and brittle hair, tendency to premature baldness, bulbous nose called pear-shaped, long and flat filter and low ear implantation. The most noticeable skeletal changes are clinodactyly, phalangeal epiphyses of the hands appearing as cone-shaped, short stature and hip joint malformations. We report a case of a teenager boy diagnosed with TRPS and referred for rheumatologic evaluation due to joint complaints.

Trichorhinophalangeal syndrome type I: a novel mutation and Perthes-like changes of the hip in a family with 4 cases over 3 generations

The trichorhinophalangeal syndrome is a rare genetic syndrome with characteristic craniofacial and skeletal abnormalities including hip pathology in variable manifestation. We describe hip involvement with Perthes-like changes and a novel mutation of the TRPSI gene in a family with 4 affected individuals. This case series underlines the clinical significance of rare genetic disorders such as TRPS that among other differential diagnoses should be kept in mind when children present with Perthes-like changes of the hip joint.

Long-term follow-up of four patients with Langer-Giedion syndrome: clinical course and complications

Long-term observations of individuals with the so-called Langer-Giedion (LGS) or tricho-rhino-phalangeal type II (TRPS2) are scarce. We report here a on follow-up of four LGS individuals, including one first described by Andres Giedion in 1969, and review the sparse publications on adults with this syndrome which comprises ectodermal dysplasia, multiple cone-shaped epiphyses prior to puberty, multiple cartilaginous exostoses, and mostly mild intellectual impairment. LGS is caused by deletion of the chromosomal segment 8q24.11-q24.13 containing among others the genes EXT1 and TRPS1. Most patients with TRPS2 are only borderline or mildly cognitively delayed, and few are of normal intelligence. Their practical skills are better than their intellectual capability, and, for this reason and because of their low self-esteem, they are often underestimated. Some patients develop seizures at variable age. Osteomas on processes of cervical vertebrae may cause pressure on cervical nerves or dissection of cerebral arteries. Joint stiffness is observed during childhood and changes later to joint laxity causing instability and proneness to trauma. Perthes disease is not rare. Almost all males become bald at or soon after puberty, and some develop (pseudo) gynecomastia. Growth hormone deficiency was found in a few patients, TSH deficiency so far only in one. Puberty and fertility are diminished, and no instance of transmission of the deletion from a non-mosaic parent to a child has been observed so far. Several affected females had vaginal atresia with consequent hydrometrocolpos.

Third case of 8q23.3-q24.13 deletion in a patient with Langer-Giedion syndrome phenotype without TRPS1 gene deletion

Langer-Giedion syndrome (LGS) is a contiguous gene syndrome caused by a hemizygous deletion on chromosome 8q23.3-q24.11 involving TRPS1 and EXT1 genes. We report on a girl with LGS phenotype and a 7.5 Mb interstitial deletion at chromosome 8q23.3-q24.13. Array-comparative genomic hybridization (a-CGH) revealed a deletion encompassing only the EXT1 and not the TRPS1 gene. Even though the deletion of TRPS1 and EXT1 genes is responsible for craniofacial and skeletal features of LGS, there have been previous reports of patients with LGS phenotype and 8q24 deletions leaving the TRPS1 gene intact. To our knowledge, this is the third such case. Our patient differs from previously reported LGS patients without TRPS1 gene deletion in that she has the typical LGS facial dysmorphism and skeletal abnormalities. However, the girl is of normal height and has only a mild developmental delay. Additionally, she has dyslalia and premature adrenarche classified as Tanner stage 3 premature pubarche which have not yet been described as features of LGS. We examine the molecular breakpoints and phenotypes of our patient and previously reported cases.

Rheumatologic and neurological events in an elderly patient with tricho-rhino-phalangeal syndrome type I

Sparse scalp hair, a peculiar shape of the nose, and cone-shaped epiphyses of the phalanges are the hallmarks of the tricho-rhino-phalangeal syndromes (TRPS). Short stature, hip dysplasia, and malformations of inner organs including mitral valve prolpase have also often been described for these conditions. Here, we described a 64-year-old woman with molecularly proved TRPS I and several atypical late-onset rheumatologic and neurological symptoms.

Disorders caused by chromosome abnormalities

Many human genetic disorders result from unbalanced chromosome abnormalities, in which there is a net gain or loss of genetic material. Such imbalances often disrupt large numbers of dosage-sensitive, developmentally important genes and result in specific and complex phenotypes. Alternately, some chromosomal syndromes may be caused by a deletion or duplication of a single gene with pleiotropic effects. Traditionally, chromosome abnormalities were identified by visual inspection of the chromosomes under a microscope. The use of molecular cytogenetic technologies, such as fluorescence in situ hybridization and microarrays, has allowed for the identification of cryptic or submicroscopic imbalances, which are not visible under the light microscope. Microarrays have allowed for the identification of numerous new syndromes through a genotype-first approach in which patients with the same or overlapping genomic alterations are identified and then the phenotypes are described. Because many chromosomal alterations are large and encompass numerous genes, the ascertainment of individuals with overlapping deletions and varying clinical features may allow researchers to narrow the region in which to search for candidate genes.

Tricho-rhino-phalangeal syndrome with supernumerary teeth

Tricho-rhino-phalangeal syndromes (TRPS) are caused by mutation or deletion of TRPS1, a gene encoding a GATA transcription factor. These disorders are characterized by abnormalities of the hair, face, and selected bones. Rare cases of individuals with TRPS displaying supernumerary teeth have been reported, but none of these has been examined molecularly. We used two different approaches to investigate a possible role of TRPS1 during tooth development. We looked at the expression of Tprs1 during mouse tooth development and analyzed the craniofacial defects of Trps1 mutant mice. In parallel, we investigated whether a 17-year-old Thai boy with clinical features of TRPS and 5 supernumerary teeth had mutation in TRPS1. We report here that Trps1 is expressed during mouse tooth development, and that an individual with TRPS with supernumerary teeth has the amino acid substitution A919V in the GATA zinc finger of TRPS1. These results suggest a role for TRPS1 in tooth morphogenesis.

Further case of microdeletion of 8q24 with phenotype overlapping Langer-Giedion without TRPS1 deletion

Langer-Giedion syndrome results from a microdeletion at 8q24.1 encompassing the EXT1 and the adjacent TRPS1 gene. We report on a boy with an oligo array-cgh characterized small microdeletion involving EXT1 alone but with some features of Langer-Giedion syndrome suggesting a functional disturbance of TRPS1. This boy, in addition to a mild Langer-Giedion like phenotype, also had some unusual features including prominent toe pads and fat pads on the soles of his feet similar to those described in Pierpont syndrome.

The discovery of microdeletion syndromes in the post-genomic era: review of the methodology and characterization of a new 1q41q42 microdeletion syndrome

PURPOSE

The advent of molecular cytogenetic technologies has altered the means by which new microdeletion syndromes are identified. Whereas the cytogenetic basis of microdeletion syndromes has traditionally depended on the serendipitous ascertainment of a patient with established clinical features and a chromosomal rearrangement visible by G-banding, comparative genomic hybridization using microarrays has enabled the identification of novel, recurrent imbalances in patients with mental retardation and apparently nonspecific features. Compared with the "phenotype-first" approach of traditional cytogenetics, array-based comparative genomic hybridization has enabled the detection of novel genomic disorders using a "genotype-first" approach. We report as an illustrative example the characterization of a novel microdeletion syndrome of 1q41q42.

METHODS

We tested more than 10,000 patients with developmental disabilities by array-based comparative genomic hybridization using our targeted microarray. High-resolution microarray analysis was performed using oligonucleotide microarrays for patients in whom deletions of 1q41q42 were identified. Fluorescence in situ hybridization was performed to confirm all 1q deletions in the patients and to exclude deletions or other chromosomal rearrangements in the parents.

RESULTS

Seven cases were found with de novo deletions of 1q41q42. The smallest region of overlap is 1.17 Mb and encompasses five genes, including DISP1, a gene involved in the sonic hedgehog signaling pathway, the deletion of which has been implicated in holoprosencephaly in mice. Although none of these patients showed frank holoprosencephaly, many had other midline defects (cleft palate, diaphragmatic hernia), seizures, and mental retardation or developmental delay. Dysmorphic features are present in all patients at varying degrees. Some patients showed more severe phenotypes and carry the clinical diagnosis of Fryns syndrome.

CONCLUSIONS

This new microdeletion syndrome with its variable clinical presentation may be responsible for a proportion of Fryns syndrome patients and adds to the increasing number of new syndromes identified with array-based comparative genomic hybridization. The genotype-first approach to identifying recurrent chromosome abnormalities is contrasted with the traditional phenotype-first approach. Targeting developmental pathways in a functional approach to diagnostics may lead to the identification of additional microdeletion syndromes.

Nablus mask-like facial syndrome is caused by a microdeletion of 8q detected by array-based comparative genomic hybridization

In 2000, Teebi reported on a 4-year-old boy with a distinctive pattern of malformation, which he termed the "Nablus mask-like facial syndrome" (OMIM# 608156). Characterization of this syndrome has been difficult because of the paucity of patients described in the medical literature and its unknown etiology and pathogenesis. We present two patients with Nablus mask-like facial syndrome who both display a microdeletion in the 8q21-8q22 region detected by array-based comparative genomic hybridization. Patient 1, a boy, has a distinct facial appearance characterized by severe blepharophimosis, tight-appearing glistening facial skin, sparse and unruly hair, a flat and broad nose, and distinctive ears that are triangular in shape with prominent antihelices. He also demonstrates camptodactyly, contractures, unusual dentition, cryptorchidism, mild developmental delay, and a happy demeanor. Patient 2, a girl with a strikingly similar phenotype, was previously described in a report by Salpietro et al. 2003. She has distinctive ears, dental anomalies, and developmental delay. The etiology of her pattern of malformation was not identified at that time. Although high-resolution chromosome and subtelomeric FISH analyses were normal, array-based comparative genomic hybridization revealed an approximately 4 Mb deletion involving the 8q21.3-8q22.1 region in both patients. This region encompasses a number of genes that may contribute to this unique phenotype. These results demonstrate a chromosomal microdeletion as the etiology of Nablus mask-like facial syndrome and emphasize the diagnostic utility of array-based comparative genomic hybridization in the evaluation of multiple malformation syndromes of previously unrecognized causation.

Lower eyelid entropion in Langer-Giedion syndrome

Langer-Giedion syndrome results from a genetic deletion on chromosome 8. Although redundant skin is part of Langer-Giedion syndrome, lower eyelid entropion and eyelid laxity have not been previously reported in the medical literature. We report a case of bilateral lower eyelid entropion in a patient with Langer-Giedion syndrome who successfully underwent entropion repair with anterior lamellar resection, lower eyelid retractor advancement, and lateral canthopexy. Although she has done well 6 months after surgery, we anticipate that laxity and eyelid instability will continue to develop with age, and additional reconstructive surgery may be required.

Pronounced short stature in a girl with tricho-rhino-phalangeal syndrome II (TRPS II, Langer-Giedion syndrome) and growth hormone deficiency

We report on a 10-year-old girl with tricho-rhino-phalangeal syndrome type II (TRPS II) and pronounced short stature (-4.8 SD). The patient has an interstitial chromosome 8q24.1 deletion of 12-15 Mb. The deletion spans all genes from CSMD3 to at least ANXA13 including the TRPS1 and EXT1 genes, which are responsible for the TRPS II phenotype. In addition to the features of TRPS II, the patient had growth hormone (GH) deficiency with diminished response in three stimulation tests. Therapy with 0.2 mg GH/kg/week led to an increase of growth velocity from 2.5 to 6.6 cm/year. To our knowledge, such a combination of TRPS II and GH deficiency has not yet been described.

Epigenetic loss of the familial tumor-suppressor gene exostosin-1 (EXT1) disrupts heparan sulfate synthesis in cancer cells

Germline mutations in the Exostoses-1 gene (EXT1) are found in hereditary multiple exostoses syndrome, which is characterized by the formation of osteochondromas and an increased risk of chondrosarcomas and osteosarcomas. However, despite its putative tumor-suppressor function, little is known of the contribution of EXT1 to human sporadic malignancies. Here, we report that EXT1 function is abrogated in human cancer cells by transcriptional silencing associated with CpG island promoter hypermethylation. We also show that, at the biochemical and cellular levels, the epigenetic inactivation of EXT1, a glycosyltransferase, leads to the loss of heparan sulfate (HS) synthesis. Reduced HS production can be reversed by the use of a DNA demethylating agent. Furthermore, the re-introduction of EXT1 into cancer cell lines displaying methylation-dependent silencing of EXT1 induces tumor-suppressor-like features, e.g. reduced colony formation density and tumor growth in nude mouse xenograft models. Screening a large collection of human cancer cell lines (n=79) and primary tumors (n=454) from different cell types, we found that EXT1 CpG island hypermethylation was common in leukemia, especially acute promyelocytic leukemia and acute lymphoblastic leukemia, and non-melanoma skin cancer. These findings highlight the importance of EXT1 epigenetic inactivation, leading to an abrogation of HS biosynthesis, in the processes of tumor onset and progression.

Multiple exostoses, mental retardation, hypertrichosis, and brain abnormalities in a boy with a de novo 8q24 submicroscopic interstitial deletion

Multiple exostoses represent a genetically heterogeneous disorder that may occur isolated or as part of a complex contiguous gene syndrome such as Langer-Giedion syndrome on chromosome 8 and the proximal 11p deletion syndrome on chromosome 11. Here we describe a boy with multiple exostoses, hypertrichosis, mental retardation, and epilepsy due to a de novo deletion on chromosome 8q24. Molecular analysis revealed that the deletion interval overlaps with the Langer-Giedion syndrome and involves the EXT1 gene and additional genes located distal to EXT1, but probably not encompassing the TRPS1 gene located proximal to EXT1.

Chromosomal abnormalities and epilepsy: a review for clinicians and gene hunters

PURPOSE

We analyzed databases on chromosomal anomalies and epilepsy to identify chromosomal regions where abnormalities are associated with clinically recognizable epilepsy syndromes. The expectation was that these regions could then be offered as targets in the search for epilepsy genes.

METHODS

The cytogenetic program of the Oxford Medical Database, and the PubMed database were used to identify chromosomal aberrations associated with seizures and/or EEG abnormalities. The literature on selected small anomalies thus identified was reviewed from a clinical and electroencephalographic viewpoint, to classify the seizures and syndromes according to the current International League Against Epilepsy (ILAE) classification.

RESULTS

There were 400 different chromosomal imbalances described with seizures or EEG abnormalities. Eight chromosomal disorders had a high association with epilepsy. These comprised: the Wolf-Hirschhorn (4p-) syndrome, Miller-Dieker syndrome (del 17p13.3), Angelman syndrome (del 15q11-q13), the inversion duplication 15 syndrome, terminal deletions of chromosome 1q and 1p, and ring chromosomes 14 and 20. Many other segments had a weaker association with seizures. The poor quality of description of the epileptology in many reports thwarted an attempt to make precise karyotype-phenotype correlations.

CONCLUSIONS

We identified certain chromosomal regions where aberrations had an evident association with seizures, and these regions may be useful targets for gene hunters. New correlations with specific epilepsy syndromes were not revealed. Clinicians should continue to search for small chromosomal abnormalities associated with specific epilepsy syndromes that could provide important clues for finding epilepsy genes, and the epileptology should be rigorously characterized.

Familial case of Potocki-Shaffer syndrome associated with microdeletion of EXT2 and ALX4

Multiple exostosis, biparietal foramina, minor craniofacial abnormalities, and mental retardation are characteristic of the syndrome associated with a proximal deletion of 11p (MIM # 601224), which has been shown to be a true contiguous gene deletion syndrome. The presence of multiple exostosis is associated with deletion of the EXT2 gene. Similarly, the presence of biparietal foramina has been shown to be associated with the deletion of ALX4 located proximally to EXT2. Specific genes related to mental retardation and craniofacial abnormalities, however, have yet to be identified. We report on a family with a microdeletion of 11(pll.2p11.2) with multiple exostosis and biparietal foramina without mental retardation or craniofacial abnormalities. Our results suggest that genes related to mental retardation and craniofacial development must be located outside of the D11S1785-D11S1385 region.

Transcriptional repression and developmental functions of the atypical vertebrate GATA protein TRPS1

Known vertebrate GATA proteins contain two zinc fingers and are required in development, whereas invertebrates express a class of essential proteins containing one GATA-type zinc finger. We isolated the gene encoding TRPS1, a vertebrate protein with a single GATA-type zinc finger. TRPS1 is highly conserved between Xenopus and mammals, and the human gene is implicated in dominantly inherited tricho-rhino-phalangeal (TRP) syndromes. TRPS1 is a nuclear protein that binds GATA sequences but fails to transactivate a GATA-dependent reporter. Instead, TRPS1 potently and specifically represses transcriptional activation mediated by other GATA factors. Repression does not occur from competition for DNA binding and depends on a C-terminal region related to repressive domains found in Ikaros proteins. During mouse development, TRPS1 expression is prominent in sites showing pathology in TRP syndromes, which are thought to result from TRPS1 haploinsufficiency. We show instead that truncating mutations identified in patients encode dominant inhibitors of wild-type TRPS1 function, suggesting an alternative mechanism for the disease. TRPS1 is the first example of a GATA protein with intrinsic transcriptional repression activity and possibly a negative regulator of GATA-dependent processes in vertebrate development.

Diminished levels of the putative tumor suppressor proteins EXT1 and EXT2 in exostosis chondrocytes

The EXT family of putative tumor suppressor genes affect endochondral bone growth, and mutations in EXT1 and EXT2 genes cause the autosomal dominant disorder Hereditary Multiple Exostoses (HME). Loss of heterozygosity (LOH) of these genes plays a role in the development of exostoses and chondrosarcomas. In this study, we characterized EXT genes in 11 exostosis chondrocyte strains using LOH and mutational analyses. We also determined subcellular localization and quantitation of EXT1 and EXT2 proteins by immunocytochemistry using antibodies raised against unique peptide epitopes. In an isolated non-HME exostosis, we detected three genetic hits: deletion of one EXT1 gene, a net 21-bp deletion within the other EXT1 gene and a deletion in intron 1 causing loss of gene product. Diminished levels of EXT1 and EXT2 protein were found in 9 (82%) and 5 (45%) exostosis chondrocyte strains, respectively, and 4 (36%) were deficient in levels of both proteins. Although we found mutations in exostosis chondrocytes, mutational analysis alone did not predict all the observed decreases in EXT gene products in exostosis chondrocytes, suggesting additional genetic mutations. Moreover, exostosis chondrocytes exhibit an unusual cellular phenotype characterized by abnormal actin bundles in the cytoplasm. These results suggest that multiple mutational steps are involved in exostosis development and that EXT genes play a role in cell signaling related to chondrocyte cytoskeleton regulation.

Genotypic and phenotypic spectrum in tricho-rhino-phalangeal syndrome types I and III

Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities. Three subtypes have been described: TRPS I, caused by mutations in the TRPS1 gene on chromosome 8; TRPS II, a microdeletion syndrome affecting the TRPS1 and EXT1 genes; and TRPS III, a form with severe brachydactyly, due to short metacarpals, and severe short stature, but without exostoses. To investigate whether TRPS III is caused by TRPS1 mutations and to establish a genotype-phenotype correlation in TRPS, we performed extensive mutation analysis and evaluated the height and degree of brachydactyly in patients with TRPS I or TRPS III. We found 35 different mutations in 44 of 51 unrelated patients. The detection rate (86%) indicates that TRPS1 is the major locus for TRPS I and TRPS III. We did not find any mutation in the parents of sporadic patients or in apparently healthy relatives of familial patients, indicating complete penetrance of TRPS1 mutations. Evaluation of skeletal abnormalities of patients with TRPS1 mutations revealed a wide clinical spectrum. The phenotype was variable in unrelated, age- and sex-matched patients with identical mutations, as well as in families. Four of the five missense mutations alter the GATA DNA-binding zinc finger, and six of the seven unrelated patients with these mutations may be classified as having TRPS III. Our data indicate that TRPS III is at the severe end of the TRPS spectrum and that it is most often caused by a specific class of mutations in the TRPS1 gene.

Molecular basis of multiple exostoses: mutations in the EXT1 and EXT2 genes

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of exostoses, which are cartilage-capped bony protuberances mainly located on long bones. Two genes, EXT1 and EXT2, and at least one other unidentified gene, are known to be involved in the formation of exostoses. To date, 49 different EXT1 and 25 different EXT2 mutations have been found in EXT patients, and there is evidence that mutations in these two genes are responsible for over 70% of the EXT cases. Among the 49 EXT1 mutations there are 9 nonsense, 21 frameshift, and 5 splice site mutations; 2 in-frame deletions of 1 and 5 amino acids respectively; and 12 missense mutations. For EXT2, 8 nonsense, 11 frameshift, 3 splice site and 3 missense mutations are described. The majority of these mutations are mutations causing loss of function, which is consistent with the presumed tumor suppressor function of the EXT genes.

Lunatomalacia associated with congenital shortening of the ulna in Langer-Giedion syndrome: a case report

A 22-year-old patient with type I trichorinophalangeal Langer-Giedion syndrome presented a stage 2 osteonecrosis of the lunate associated with congenital shortening of the ulna and carpal tunnel syndrome. The patient was treated by shortening osteotomy of the radius and median nerve neurolysis, with an excellent result. This case provides an additional piece of evidence associating ulnar-minus variance with lunatomalacia, and another argument in favor of the theory that Kienböck's disease results from microfractures sustained by the lunate under an abnormal stress distribution situation.

Monosomy 8q: prenatal diagnosis and autopsy findings

The autopsy findings of a fetus with deletion of the long arm of chromosome 8 are described. Many of the features are similar to those of the tricho-rhino-phalangeal syndromes, types I and II, which are associated with deletions on chromosome 8q24. Other findings in this case, such as total absence of the corpus callosum and intestinal malrotation, have not been described in these syndromes. Genes involved in the development of the latter malformations may reside in adjacent regions on the long arm of chromosome 8. An elevated serum level of beta human chorionic gonadotropin (beta hCG) was found during pregnancy. This aberration should be included with other chromosomal disorders which may be detected by this test.

Association of myopathy with multiple exostoses and mental retardation: a case report

We report an 18-year-old male with multiple exostoses, dysmorphic features, mental retardation and myopathy. The case is discussed in the light of previously reported disorders in which multiple exostoses are associated with neurological impairment.

Syndromes associated with melanocytic nevi

Melanocytic nevi have been reported in association with several congenital syndromes. This review describes the clinical and cutaneous manifestations of six syndromes associated with congenital melanocytic nevi, two associated with acquired nevi, and six associated with melanocytic nevi in which insufficient evidence exists to classify them as congenital or acquired. It is important to recognize these associations to evaluate and counsel patients with melanocytic nevi. Early recognition will also facilitate timely intervention.

Tricho-rhino-phalangeal syndrome type I (TRP I) due to an apparently balanced translocation involving 8q24

Tricho-rhino-phalangeal (TRP) syndromes type I and II are caused by a defective gene located on chromosome 8q24.1. We report a family with 2 sibs affected with TRP type I in combination with an apparently balanced chromosome (8;18) translocation involving 8q24.11. It is very likely that the 8q24 translocation breakpoint is physically linked to the TRP gene(s), thereby facilitating future efforts to clone the TRP gene(s).

Tricho-rhino-phalangeal syndrome type II (Langer-Giedion) with persistent cloaca and prune belly sequence in a girl with 8q interstitial deletion

A patient with the diagnosis of Langer-Giedion syndrome (tricho-rhino-phalangeal syndrome type II) and interstitial 8q deletion was also noted to have persistent cloaca and prune belly sequence. This is the first report of this association. If it postulated that these latter embryonic defects may be due to the chromosome abnormality, supporting the definition of contiguous gene syndrome.

The gene for hereditary multiple exostoses does not map to the Langer-Giedion region (8q23-q24)

Hereditary multiple exostoses is a dominantly inherited skeletal disorder which alters enchondral bone during growth and is characterised by exostoses of the juxta-epiphyseal regions. Using polymorphic DNA probes, we have been able to exclude the disease gene from close proximity to the 8q24.1 region where a dominant syndrome with multiple exostoses, the trichorhinophalangeal syndrome type II (TRP II, Langer-Giedion syndrome, MIM 15025), has been previously localised (pairwise linkage Z = -8.96 at theta = 0 with probe L48 at locus D8S51). Multipoint linkage analysis using probes L48, L24, and L1 consistently excluded the HME gene from a large area of the distal long arm of chromosome 8, spanning the smallest region of overlap assigned to the TRP II gene. These studies support the clinical view that HME and TRP II are distinct entities.

Multiple exostoses in a patient with t(8;11)(q24.11;p15.5)

The occurrence of multiple exostoses in a carrier of a balanced translocation t(8;11) (q24.11;p15.5) is described. The breakpoint on chromosome 8 is at proximal q24.1 within the critical region reported for Langer-Giedion syndrome.