Complex chromosomal rearrangements causing Langer-Giedion syndrome atypical phenotype: genotype-phenotype correlation and literature review

Minimal Critical Region and Genes for a Typical Presentation of Langer-Giedion Syndrome

Langer-Giedion syndrome (LGS) is caused by a contiguous deletion at 8q23q24, characterized by exostoses, facial, ectodermal, and skeletal anomalies, and, occasionally, intellectual disability. LGS patients have been diagnosed clinically or by routine cytogenetic techniques, hampering the definition of an accurate genotype-phenotype correlation for the syndrome. We report two unrelated patients with 8q23q24 deletions, characterized by cytogenomic techniques, with one of them, to our knowledge, carrying the smallest deletion reported in classic LGS cases. We assessed the pathogenicity of the deletion of genes within the 8q23q24 region and reviewed other molecularly confirmed cases from the literature. Our findings suggest a 3.2-Mb critical region for a typical presentation of the syndrome, emphasizing the contribution of the TRPS1, RAD21, and EXT1 genes' haploinsufficiency, and facial dysmorphisms as well as bone anomalies as the most frequent features among patients with LGS. We also suggest a possible role for the CSMD3 gene, whose deletion seems to contribute to central nervous system anomalies. Since studies performing such correlation for LGS patients are limited, our data contribute to improving the ge-notype-phenotype characterization for LGS patients.

Multiple hereditary exostoses and enchondromatosis

Multiple hereditary exostoses (MHE) and enchondromatosis are rare multifocal benign disorders usually causing skeletal deformities appearing already in childhood. MHE is a dominant autosomal inherited disorder characterized by multiple osteochondromas (exostoses) growing outward from the metaphyses of long bones as well as from flat bones. They may cause reduced joint motion and pain due to tendon, muscle, and nerve compression. Enchondromatosis (or Ollier's disease) is a noninherited disorder characterized by the presence of multiple intraosseous enchondromas located asymmetrically in the skeleton and with a wide variation regarding location, size, and number ranging from the involvement of a single hand to the involvement of the entire skeleton. It can occur together with soft-tissue hemangiomas in Maffucci's syndrome. Clinical problems caused by the enchondromas are mainly related to skeletal deformities causing malalignment and restricted motion of joint. In both disorders, there is a risk of malignant transformation as well as secondary degenerative joint changes.

Mixed Phenotype of Langer-Giedion's and Cornelia de Lange's Syndromes in an 8q23.3-q24.1 Microdeletion without TRPS1 Deletion

Langer-Giedion's syndrome (LGS) or trichorhinophalangeal syndrome type II (TRPS II; MIM:150230) is a contiguous gene deletion syndrome caused by the haploinsufficiency of the TRPS1 and EXT1 genes. Cornelia de Lange's syndrome (CdLS) is a genetically heterogeneous dysmorphic syndrome where heterozygous mutations of RAD21 gene have been associated with a mild clinical presentation (CDLS type 4; MIM: 614701). We report a female patient with a 2.3-Mb interstitial deletion at 8q23.3-q24.1 encompassing EXT1 and RAD21 genes but not TRPS1 . Clinical findings in this patient are correlated with a mixed phenotype of LGS and CdLS type 4.

Hereditary Multiple Exostoses: Current Insights

Hereditary multiple exostoses (HME), also called hereditary multiple osteochondromas, is a rare genetic disorder characterized by multiple osteochondromas that grow near the growth plates of bones such as the ribs, pelvis, vertebrae and especially long bones. The disease presents with various clinical manifestations including chronic pain syndromes, restricted range of motion, limb deformity, short stature, scoliosis and neurovascular alteration. Malignant transformation of exostosis is rarely seen. The disease has no medical treatment and surgery is only recommended in symptomatic exostoses or in cases where a malignant transformation is suspected. HME is mainly caused by mutations and functional loss of the EXT1 and EXT2 genes which encode glycosyltransferases, an enzyme family involved in heparan sulfate (HS) synthesis. However, the peculiar molecular mechanism that leads to the structural changes of the cartilage and to osteochondroma formation is still being studied. Basic science studies have recently shown new insights about altering the molecular and cellular mechanism caused by HS deficiency. Pediatricians, geneticists and orthopedic surgeons play an important role in the study and treatment of this severe pathology. Despite the recent significant advances, we still need novel insights to better specify the role of HS in signal transduction. The purpose of this review was to analyze the most relevant aspects of HME from the literature review, give readers an important tool to understand its clinical features and metabolic-pathogenetic mechanism, and to identify an effective treatment method. We focused on the aspects of the disease related to clinical management and surgical treatment in order to give up-to-date information that could be useful for following best clinical practice.

Hereditary Multiple Exostoses: a review of clinical appearance and metabolic pattern

Hereditary multiple exostoses (HME) is an inherited genetic condition characterized by the presence of multiple exostoses (osteochondromas). MHE is a relatively rare autosomal dominant disorder, mainly caused by loss of function mutations in two genes: exostosin-1 (EXT1) and exostosin-2 (EXT2). These genes are linked to heparan sulfate (HS) synthesis, but the specific molecular mechanism leading to the disruption of the cartilage structure and the consequent exostoses formation is still not resolved. The aim of this paper is to encounter the main aspects of HME reviewing the literature, in order to improve clinical features and evolution, and the metabolic-pathogenetic mechanisms underlying. Although MHE may be asymptomatic, a wide spectrum of clinical manifestations is found in paediatric patients with this disorder. Pain is experienced by the majority of patients, even restricted motion of the joint is often encountered. Sometimes exostoses can interfere with normal development of the growth plate, giving rise to limb deformities, low stature and scoliosis. Other many neurovascular and associated disorders can lead to surgery. The most feared complication is the malignant transformation of an existing osteochondroma into a secondary peripheral chondrosarcoma, during adulthood. The therapeutic approach to HME is substantially surgical, whereas the medical one is still at an experimental level. In conclusion, HME is a complex disease where the paediatrician, the geneticist and the orthopaedic surgeon play an interchangeable role in diagnosis, research and therapy. We are waiting for new studies able to explain better the role of HS in signal transduction, because it plays a role in other bone and cartilage diseases (in particular malignant degeneration) as well as in skeletal embryology.

An interstitial deletion at 8q23.1-q24.12 associated with Langer-Giedion syndrome/ Trichorhinophalangeal syndrome (TRPS) type II and Cornelia de Lange syndrome 4

Background

There are three distinct subtypes of Trichorhinophalangeal syndrome (TRPS); TRPS type I, TRPS type II and TRPS type III. Features common to all three subtypes include sparse, slowly growing scalp hair, laterally sparse eyebrows, a bulbous tip of the nose (pear-shaped), and protruding ears. Langer–Giedion syndrome (LGS) or TRPS type II is a contiguous gene syndrome on 8q24.1, involving loss of functional copies of the TRPS1 and EXT1 genes. We report a male patient that was referred to the Department of Medical Genetics due to hypotonia and dysmorphic facial features.

Results

Cytogenetic and array- Comparative Genomic Hybridization (aCGH) analysis revealed that the patient was a carrier of an interstitial deletion at 8q23.1-q24.12 of 12,5 Mb. Parental karyotype indicated that the father carried an apparently balanced insertion: 46, ΧΥ, der(10)ins(10;8)(q22;q23q24).

Conclusions

This is the first report of an apparently balanced insertion including chromosomes 8 and 10 contributing to the etiology of LGS/ TRPS type II. Τimely diagnosis of parental balanced chromosomal rearrangements can reduce the risk of subsequent miscarriages as well as abnormal offspring.

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.