Franceschetti syndrome in a child with a de novo balanced translocation (5;13)(q11;p11) and significant decrease of hexosaminidase B

Cytogenetic and clinical assessment of a family with treacher collins syndrome

Treacher Collins syndrome (TCS) is a rare autosomal dominant disorder characterized by craniofacial deformities. It is the most common type of mandibulofacial dysostosis (MFD). The objective of this study is to do cytogenetic analysis of a TCS family. Physical examination and all available medical records were reviewed. 50 GTG-banded metaphases were analysed to detect any structural or numerical chromosomal abnormality. Downward slanting of palpebral fissures, hypoplasia of zygomatic arch complex, and hypoplasia of mandible were present in all. Cytogenetic findings show interstitial deletion in chromosomes 5(q32-q33) and 3(q23-q25). We report four members of three generations of a family having TCS in a unique way that the deletion has been found in 3q and 5q which has not been reported. Mosaicism of deletion on 5q was detected in all affected members whereas 3q deletion was found only in one member (II.2). This finding may represent a more severe manifestation of the TCS. Thus the evaluation and counselling of the TCS patients should be undertaken with caution.

Mandibulofacial dysostosis in a patient with a de novo 2;17 translocation that disrupts the HOXD gene cluster

Treacher Collins syndrome (TCS) is the prototypical mandibulofacial dysostosis syndrome, but other mandibulofacial dysostosis syndromes have been described. We report an infant with mandibulofacial dysostosis and an apparently balanced de novo 2;17 translocation. She presented with severe lower eyelid colobomas requiring skin grafting, malar and mandibular hypoplasia, bilateral microtia with external auditory canal atreasia, dysplastic ossicles, hearing loss, bilateral choanal stenosis, cleft palate without cleft lip, several oral frenula of the upper lip/gum, and micrognathia requiring tracheostomy. Her limbs were normal. Chromosome analysis at the 600-band level showed a 46,XX,t(2;17)(q24.3;q23) karyotype. Sequencing of the entire TCOF1 coding region did not show evidence of a sequence variation. High-resolution genomic microarray analysis did not identify a cryptic imbalance. FISH mapping refined the breakpoints to 2q31.1 and 17q24.3-25.1 and showed the 2q31.1 breakpoint likely affects the HOXD gene cluster. Several atypical findings and lack of an identifiable TCOF1 mutation suggest that this child has a provisionally unique mandibulofacial dysostosis syndrome. The apparently balanced de novo translocation provides candidate loci for atypical and TCOF1 mutation negative cases of TCS. Based on the agreement of our findings with one previous case of mandibulofacial dysostosis with a 2q31.1 transocation, we hypothesize that misexpression of genes in the HOXD gene cluster produced the described phenotype in this patient.

Treacher Collins syndrome

Treacher Collins syndrome is an autosomal dominant disorder of craniofacial development, the features of which include conductive hearing loss and cleft palate. In the absence of a candidate gene, a positional cloning approach has been used to isolate the mutated gene which maps to chromosome 5q31.3-32. Flanking markers were identified and a yeast artificial chromosome and cosmid contig of the region defined by these markers was created as a prelude to the creation of a transcript map of the region. Analysis of genes isolated using this approach resulted in the identification of the mutated gene. While the function of the gene remains unknown, the identification of 20 mutations spread throughout the gene, all of which would result in the insertion of a premature termination codon into the reading frame, suggests that the mechanism underlying the disease is haploinsufficiency.

Prenatal diagnosis in Treacher Collins syndrome using combined linkage analysis and ultrasound imaging

Treacher Collins syndrome is an autosomal dominant disorder of facial development, the features of which include conductive hearing loss and cleft palate. In the current investigation, linkage analysis has been used to make first trimester diagnostic predictions in a pregnancy at high risk of producing an affected child. The results of this analysis predicted that the child would be affected. As predictions of the severity of the disease were not possible, the pregnancy was also assessed by ultrasound imaging. This confirmed the affected diagnosis and predicted that the child would be severely affected.

Positional cloning of a gene involved in the pathogenesis of Treacher Collins syndrome. The Treacher Collins Syndrome Collaborative Group

Treacher Collins syndrome is an autosomal dominant disorder of craniofacial development, which has been localized to chromosome 5q32-33.1. In the present study, the isolation of new polymorphic markers has allowed the identification of overlapping recombination events in two affected individuals. Extension of the transcription map of the critical region proximally has resulted in the isolation of a new gene (which has been named Treacle) of unknown function. The identification of different mutations in five unrelated families, all of which would result in premature termination of the predicted protein, indicates that the Treacher Collins syndrome gene has been positionally cloned.

Treacher Collins syndrome

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Molecular genetic approaches to the study of human craniofacial dysmorphologies

Craniofacial dysmorphologies are common, ranging from simple facial disfigurement to complex malformations involving the whole head. With the advent of gene mapping and cloning techniques, the genetic element of both simple and complex human craniofacial dysmorphologies can be investigated. For many of the dysmorphic syndromes, it is possible to find families that display a particular phenotype in either an autosomal dominant, recessive, or X-linked manner. This article focuses on a subgroup of craniofacial dysmorphologies, covering these three main inheritance patterns, that are being studied using molecular biology techniques: DiGeorge syndrome, Treacher Collins syndrome, Greig cephalopolysyndactyly syndrome, acrocallosal syndrome, amelogenesis imperfecta, and X-linked cleft palate with ankyloglossia. Once the mutated or deleted gene or genes for each syndrome have been cloned, patterns of normal and abnormal craniofacial development should be elucidated. This should enhance both diagnosis and treatment of these common and disfiguring disorders.

Mandibulofacial dysostosis: report on two Brazilian families suggesting autosomal recessive inheritance

We report on mandibulofacial dysostosis in 2 brothers born to normal nonconsanguineous parents, and a girl (F = 1/16) born to normal consanguineous parents. Normal clinical, skeletal, audiologic, and cephalometric studies in the parents, as well as the absence of limb anomalies in these children, exclude the autosomal recessive (Nager and Genée-Widemann) mandibulofacial dysostoses. The data of the present patients associated with the few additional reports on mandibulofacial dysostosis recurring in sibs, suggest the possibility of an autosomal recessive Treacher Collins-like mandibulofacial dysostosis.

Mild mandibulofacial dysostosis in a child with a deletion of 3p

We report on a patient with mild mandibulofacial dysostosis and a small interstitial deletion of 3p, 46,XY,del(3)(p23p24.12). Linkage of Treacher Collins syndrome, the most common of the mandibulofacial dysostoses, to the 5q31.3-->q33.3 region of chromosome 5 has been established. This is the fourth report of a patient with mandibulofacial dysostosis with a chromosome abnormality outside the 5q31.3 area. Mandibulofacial dysostosis is a heterogeneous entity, and evaluation and counseling of affected individuals should be undertaken with caution.

Gene mapping of ocular diseases

Increasing awareness of the role of genetic factors in the causation of many human eye diseases has made ocular genetics one of the fastest growing areas of ophthalmology. The objective of this paper is to present the basic principles of gene mapping and their application to ophthalmology. The techniques used to map the genome are reviewed with emphasis placed on molecular genetics. The advances in this area have already provided the major impetus to the areas of diagnosis and prevention of some genetic eye disorders. Tables are presented that list the autosomal, X-linked and mitochondrial assignment of eye genes and disorders with ocular involvement.

Chromosomal deletion 4p15.32----p14 in a Treacher Collins syndrome patient: exclusion of the disease locus from and mapping of anonymous DNA sequences to this region

Treacher Collins syndrome is an autosomal dominant condition of bilateral craniofacial abnormalities of structures derived from the first and second branchial arches. A patient with severe manifestations of Treacher Collins syndrome and a de novo chromosomal deletion in region 4p15.32----p14 was identified. Anonymous DNA sequences of loci D4S18, D4S19, D4S20, D4S22, and D4S23 were mapped to the deleted region. DNA probes previously mapped to loci on chromosome 4p (D4S10, D4S15, D4S16, D4S26, D4S35, D4S95, D4S144, RAF1P1, QDPR, and HOX7) were not deleted in this patient. Linkage analysis between the D4S18, D4S23, and QDPR loci and Treacher Collins syndrome in eight families excluded the Treacher Collins syndrome locus from the region of the deletion.

Sandhoff disease mimicking adult-onset bulbospinal neuronopathy

A 32 year old male is described with an onset of upper limb postural tremor in adolescence followed by muscle cramps. Progressive proximal amyotrophy and weakness in the limbs developed late in the third decade. Examination disclosed, in addition, bilateral facial weakness and mild dysarthria. Enzyme studies revealed hexosaminidase A and B deficiency, indicating a diagnosis of Sandhoff disease. Intra-axonal membranocytoplasmic bodies were present in a rectal biopsy. The presentation, which resembled that of X-linked bulbospinal neuronopathy, widens the clinical spectrum for disorders related to G(M2) gangliosidosis.

Retinal cone dysfunction and mental retardation associated with a de novo balanced translocation 1;6(q44;q27)

The authors describe a six-year-old boy with cone dystrophy, mental retardation, facial dysmorphism and short neck, hands and feet in whom they found a 1:6 chromosomal translocation. This is the first description of retinal cone dystrophy and a chromosomal aberration. The hypothesize that the cone dystrophy in the patient may be assigned to 1q44 or 6q27.

A new autosomal dominant acrofacial dysostosis syndrome

We report on a family in which a previously undescribed acrofacial dysostosis syndrome is segregating as an autosomal dominant trait. Craniofacial manifestations are those of mild mandibulofacial dysostosis and are quite constant among affected relatives. The acral abnormalities are quite variable, affecting predominantly the radial ray. Variability extends from thumb duplication in one patient to mild hypoplasia of the first metacarpal and first proximal phalanx in most affected individuals. Mandibulofacial dysostosis is a causally nonspecific malformation and as such represents an apparently monotopic developmental field defect. Its occurrence with acral anomalies in several conditions of different cause represents a polytopic developmental field defect.

Mandibulofacial dysostosis in Hutterite sibs: a possible recessive trait

We report on two sisters with mandibulofacial dysostosis (MFD). Both parents were examined carefully by clinical, radiographic, audiologic, and cephalometric methods. Neither showed evidence of the MFD gene. Photographs of three grandparents and examination of one disclosed no evidence of MFD. The parents are from the Hutterite Brethren and are consanguineous. Examination of the literature on MFD disclosed a number of other families with affected sibs and apparently normal parents. These families raise the possibility of an autosomal recessive form of MFD or some other explanation such as germinal mosaicism, chromosome rearrangement, or delayed mutation. For our family, the recurrence risk is probably 25%, but since germinal mosaicism cannot be excluded, it could be as high as 50%.

Bilateral retinoblastoma with de novo constitutional balanced translocation t(2;9)(q11;p11)

The case of a 6-year-old boy with bilateral retinoblastoma (RB) and apparently de novo balanced translocation t(2;9)(q11;p11) is presented. The normality of 13q14 chromosome region has been confirmed using high resolution techniques and Esterase D assay. The hypothesis that this RB might be correlated to the translocation is discussed.

Prader-Willi syndrome and chromosome 15. A clinical discussion of 20 cases

A chromosome 15 anomaly was observed in 12 of 20 patients, 17 of whom were clinically suspected of having Prader-Willi syndrome (PWS). The clinical features of eight cases with 15q11-12 deletion were very similar to those originally described in PWS. On the other hand, the group of normal karyotype patients is heterogeneous, and their features do not strictly correspond to the clinical definition of PWS. However, the hypothesis that PWS is associated with deletion of 15q11-12 can neither explain the apparently balanced translocations of chromosome 15 nor account for the small supernumerary metacentric chromosomes corresponding to an isochromosome 15 for band 15q11 observed in some cases.