Tibial hemimelia in Langer-Giedion syndrome with 8q23.1-q24.12 interstitial deletion

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.

Congenital Tibial Deficiency

Congenital tibial deficiency is a rare condition characterized by partial to complete absence of the tibia, an intact but frequently overgrown fibula, variable degrees of knee deformity and function, and an abnormal equinovarus foot. It can occur in isolation but also presents concurrently with other orthopaedic anomalies and syndromic conditions. Among these, congenital abnormalities of the hand and femur are most commonly observed. Many theories exist regarding its etiology and some genetic mutations have been identified; however, the underlying mechanism remains unknown. The prognosis and treatment differ based on the clinical severity. The goal of treatment is always to create a stable, functional limb, most commonly with amputation and use of prosthetics. Controversy exists over the level of amputation and the usefulness of reconstructive procedures to preserve the foot and limb length. Current investigation on this complex disorder is focused on identifying its origins and further developing a classification-based treatment algorithm to improve patient outcomes.

Functional Assessment in Tibial Hemimelia (Can We Also Save the Foot in Reconstruction?)

BACKGROUND

The congenital absence of the tibia is a rare disease, and an orthopaedic surgeon may not encounter such cases during the course of his/her career. This is the largest report to date of the management of such cases by a single surgeon. The foot and leg were persevered in the majority of the cases, and a functional evaluation system was used to report outcomes.

METHODS

Thirty-six patients with tibial hemimelia, who had been under the direct care of the authors since infancy, were evaluated clinically and radiographically. The patients or their parents filled out the Pediatric Quality of Life and the parents' satisfaction forms. The surgical interventions performed, and their effects on school attendance and, and also the shoe type they wore were documented.

RESULTS

Thirty-six patients (19 girls and 17 boys) with 48 tibial-deficient limbs (19 right, 5 left, and 12 both right and left sides) were studied. The patients were assessed at 12 years (2.5 to 32.5 y), with a mean follow-up of 9 years (2 to 23 y). The 48 limbs included 14 type I, 16 type II, 11 type IV, and 7 unclassified by using the Jones classification; and 6 type I, 11 type II, 16 type III, 1 type IV, and 14 type VII by using the Weber classification. Primary amputation was performed in 8 patients (10 limbs) and limb preservation surgeries on 38 legs (28 patients). Tibiofibular synostosis, centralization of the ankle, and Ilizarov lengthening were the most common procedures. Nonunion of tibiofibular synostosis (2 cases) and knee stiffness (6 cases) were the main complications. Among the reconstructed limbs, 12 were in regular and 18 in modified shoes. The Pediatric Quality of Life of 68 points in the reconstructed group was a significant achievement, and it was also better than the score of patients who had undergone amputation.

CONCLUSION

Reconstruction of tibial hemimelia with foot preservation provides good functional outcome in the majority of cases.

LEVEL OF EVIDENCE

Level IV.

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

Langer-Giedion syndrome (LGS) is caused by a deletion of chromosome 8q23.3-q24.11. The LGS clinical spectrum includes intellectual disability (ID), short stature, microcephaly, facial dysmorphisms, exostoses. We describe a 4-year-old girl with ID, short stature, microcephaly, distinctive facial phenotype, skeletal signs (exostoses on the left fibula, coccyx agenesis, stubby and dysmorphic sphenoid bone, osteoporosis), central nervous system malformations (hypoplastic and dysmorphic corpus callosum and septum pellucidum), pituitary gland hypoplasia and hyperreninemia. Array-CGH revealed complex chromosomal rearrangements. A diagnosis of LGS was confirmed by the detection of a 8q23.3-q24.1 deletion. Associated chromosomal abnormalities were a 21q22.1 deletion and a balanced reciprocal translocation t(2;11)(p24;p15) de novo, confirmed by FISH analysis. We document the patient's atypical findings, never described in LGS patients, in order to update the genotype-phenotype correlation. We speculate that the disruption of regulatory elements mapping upstream CYP11B2 involved in the deleted region could cause hyperreninemia.

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.