1/161. Delineation of two distinct 6p deletion syndromes.Deletions of the short arm of chromosome 6 are relatively rare, the main features being developmental delay, craniofacial malformations, hypotonia, and defects of the heart and kidney, with hydrocephalus and eye abnormalities occurring in some instances. We present the molecular cytogenetic investigation of six cases with 6p deletions and two cases with unbalanced translocations resulting in monosomy of the distal part of 6p. The breakpoints of the deletions have been determined accurately by using 55 well-mapped probes and fluorescence in situ hybridization (FISH). The cases can be grouped into two distinct categories: interstitial deletions within the 6p22-p24 segment and terminal deletions within the 6p24-pter segment. Characteristics correlating with specific regions are: short neck, clinodactyly or syndactyly, brain, heart and kidney defects with deletions within 6p23-p24; and corneal opacities/iris coloboma/Rieger anomaly, hypertelorism and deafness with deletions of 6p25. The two cases with unbalanced translocations presented with a Larsen-like syndrome including some characteristics of the 6p deletion syndrome, which can be explained by the deletion of 6p25. Such investigation of cytogenetic abnormalities of 6p using FISH techniques and a defined set of probes will allow a direct comparison of reported cases and enable more accurate diagnosis as well as prognosis in patients with 6p deletions.- - - - - - - - - - ranking = 1keywords = chromosome (Clic here for more details about this article) |
2/161. Two cases of terminal deletion of chromosome 13: clinical features, conventional and molecular cytogenetic analysis.We report the cases of two unrelated patients with psychomotor retardation and craniofacial abnormalities, in whom cytogenetic studies have revealed a terminal deletion of chromosome 13 confirmed by fluorescence in situ hybridization (FISH). This del(13)(q33.2) is the smallest terminal deletion of the 13q reported so far. Interestingly enough, the serum level of coagulation factors VII and X, whose genes are located in 13q34, were reduced in both patients. These cases illustrate the difficulties in identifying precisely chromosome deletions and demonstrate that FISH techniques allow to obtain a more precise correlation between clinical phenotype and cytogenetic abnormalities.- - - - - - - - - - ranking = 6keywords = chromosome (Clic here for more details about this article) |
3/161. The smith-magenis syndrome: a new case with infant spasms.The smith-magenis syndrome (SMS) is characterized by congenital anomalies, mental retardation and the interstitial deletion of the 17p. 11.2 chromosome. The subjects affected by this syndrome show cranio-facial dysmorphias, brachycephalia, skeletal, ocular, cardiac, genitourinary and otolaryngological anomalies. The central nervous system is affected and this may be shown by psychomotor retardation, intellective deficit, electroencephalographic alterations (reduced/missing REM phase); the neuroradiological tests detect megacisterna magna, cerebellar hypoplasia, cortical dysplasia, ventricular asymmetry. Behavioural troubles are frequent and, among them, self-aggressive conducts (tearing out the nails). The syndrome is associated with the interstitial deletion of the 17p. 11.2 chromosome. The diagnosis can be made in the pre-natal period and a mosaic situation is possible. Even though the cases of SMS reported in the literature allow defining a characteristic phenotype, studies have been carried out to quantify the deletion of the chromosome 17 in order to identify the chromosomic tract which is responsible for the phenotypical induction. The deletion can either appear de novo or come from one of the parents. In addition, these subjects can show peripheral neuropathy, missing or reduced deep tendon reflexes and (rarely) epileptic crises. However, by reviewing the literature, no descriptions of patients affected by infant spasms are pointed out. This report refers to a new case of smith-magenis syndrome in a nine-month-old girl with spasms in extension.- - - - - - - - - - ranking = 3keywords = chromosome (Clic here for more details about this article) |
4/161. Mutations in the homeodomain of the human SIX3 gene cause holoprosencephaly.holoprosencephaly (HPE) is a common, severe malformation of the brain that involves separation of the central nervous system into left and right halves. Mild HPE can consist of signs such as a single central incisor, hypotelorism, microcephaly, or other craniofacial findings that can be present with or without associated brain malformations. The aetiology of HPE is extremely heterogeneous, with the proposed participation of a minimum of 12 HPE-associated genetic loci as well as the causal involvement of specific teratogens acting at the earliest stages of neurulation. The HPE2 locus was recently characterized as a 1-Mb interval on human chromosome 2p21 that contained a gene associated with HPE. A minimal critical region was defined by a set of six overlapping deletions and three clustered translocations in HPE patients. We describe here the isolation and characterization of the human homeobox-containing SIX3 gene from the HPE2 minimal critical region (MCR). We show that at least 2 of the HPE-associated translocation breakpoints in 2p21 are less than 200 kb from the 5' end of SIX3. Mutational analysis has identified four different mutations in the homeodomain of SIX3 that are predicted to interfere with transcriptional activation and are associated with HPE. We propose that SIX3 is the HPE2 gene, essential for the development of the anterior neural plate and eye in humans.- - - - - - - - - - ranking = 1keywords = chromosome (Clic here for more details about this article) |
5/161. De novo complete trisomy 5p: clinical report and FISH studies.We describe a de novo trisomy 5p in a 1-year-old severely retarded boy. The complete short arm of chromosome 5 segregated as an additional marker chromosome in all metaphases. The marker was identified as 5p by conventional cytogenetic techniques (GTG, GBG, CBG) and molecular cytogenetic techniques (whole chromosome-painting probe, probes for the cri-du-chat region and the centromere, and additionally high-resolution multicolor banding using a chromosome 5-specific dna probe cocktail). The clinical findings were similar to the established trisomy 5p phenotype including macrocephaly, facial abnormalities, tracheobronchial defects with subsequent respiratory infections, hypotonia, and psychomotor retardation. To the best of our knowledge this is the first description of an isolated complete 5p trisomy without involvement of the aberrant chromosome in any structural chromosomal rearrangements.- - - - - - - - - - ranking = 5keywords = chromosome (Clic here for more details about this article) |
6/161. Mosaic tetrasomy 9p in a girl with multiple congenital anomalies: cytogenetic and molecular-cytogenetic studies.We report on a 16-year-old girl with tetrasomy 9p mosaicism. Clinical investigations disclosed a malformation syndrome with craniofacial abnormalities, dysplasia of the right clavicle, short neck with cervical ribs, patella dislocation, Dandy-Walker malformation, mental retardation and blindness. karyotype analysis of blood lymphocytes indicated an additional marker in the size of a C-group chromosome with a large heterochromatic block in 88% of the investigated metaphases. The origin and structure of this additional marker could not be determined by chromosome banding. Application of fluorescence in situ hybridisation and comparative genomic hybridisation identified the origin of the marker chromosome, demonstrating the effectiveness of molecular-cytogenetic investigations in the diagnosis of structural and numerical chromosome abnormalities.- - - - - - - - - - ranking = 4keywords = chromosome (Clic here for more details about this article) |
7/161. Duplication of 7p21.2-->pter due to maternal 7p;21q translocation: implications for critical segment assignment in the 7p duplication syndrome.We describe a 1-year-old boy with mental and physical retardation, a large anterior fontanel, brachycephaly with flat occiput, short and stubby fingers, generalized hypotonia, ocular hypertelorism, low-nasal bridge, long philtrum, high-narrow palate, apparently low-set ears, and a small mandible. cytogenetic analysis utilizing high resolution chromosome banding technique showed an unbalanced karyotype consisting of 46,XY,add(21)(q22.3) that originated from maternal balanced translocation between chromosomes 7 and 21. fluorescence in situ hybridization (FISH) using micro-dissected library probe pool from chromosome 7 confirmed the additional material on 21q was derived from chromosome 7. Our results indicated that the patient had an unbalanced translocation, 46,XY, der(21)t(7;21)(p21.2;q22.3)mat, which resulted in duplication for distal 7p. Our patient is similar to reported cases with a 7p15-->pter or larger duplication of 7p, suggesting that the critical segment causing the characteristic phenotype of 7p duplication syndrome, including large anterior fontanel, exists at 7p21.2 or 7p21.2-->pter.- - - - - - - - - - ranking = 4keywords = chromosome (Clic here for more details about this article) |
8/161. 46, XY, del (3) (pter-->p25) syndrome: further delineation of the clinical phenotype.A boy with monosomy for the distal part of the short arm of chromosome 3 is described. The clinical features this patient has in common with the previously reported cases include pre- and post-natal growth delay, microcephaly, craniofacial dysmorphism and mental retardation. In addition, minor abnormalities not previously reported were observed, such as snapping thumbs, dorsiflected big toes, connecting anterior and posterior fontanelles at birth, nasolacrimal duct stenosis and double urethral meatus.Conclusion These five new clinical findings may help in further delineation of the syndrome and allow its early recognition. A complete revision of clinical findings published in literature is reported.- - - - - - - - - - ranking = 1keywords = chromosome (Clic here for more details about this article) |
9/161. Interstitial tandem duplication of 6p: a case with partial trisomy (6)(p12p21.3).A de novo interstitial tandem duplication of 6p12p21.3 was observed in a 7-month-old boy with growth retardation, psychomotor delay and craniofacial, brain, limb, and genital anomalies. Fluorescent in situ hybridization using a chromosome 6 paint probe demonstrated that the extra material belonged to chromosome 6. Although it has been suggested that 6p25 is the critical band involved in the expression of the phenotype of 6p duplication, comparison of the clinical findings of this case with those from the literature cases showed strong similarities.- - - - - - - - - - ranking = 2keywords = chromosome (Clic here for more details about this article) |
10/161. Apparent sotos syndrome (cerebral gigantism) in a child with trisomy 20p11.2-p12.1 mosaicism.We report on a child with apparent sotos syndrome (cerebral gigantism) and partial duplication of the short arm of chromosome 20 mosaicism. trisomy 20p11.2-p12.1 was diagnosed using cytogenetic and FISH studies. The somatostatin receptor 4 (SSTR4) gene is included in the duplicated segment. This suggests that a dosage effect of this gene might be related to some of the clinical findings observed in our patient. The present observation emphasizes the importance of chromosome analysis in patients with well-delineated but sporadic conditions.- - - - - - - - - - ranking = 2keywords = chromosome (Clic here for more details about this article) |
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