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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Here we describe a foetus with intrauterine growth retardation (IUGR), cerebral malformations and a 46,XY,der(1),t(1;6)(p36.3;q25.2) karyotype owing to a familial cryptic translocation segregating in three generations. A balanced translocation was present in the mother, the maternal uncle, the aunt and the grandmother. A female first cousin with dysmorphisms, hydrocephalus and mental retardation was a carrier of a partial trisomy 1p and a partial monosomy 6q. Multiple miscarriages were present in the family pedigree. Parents of the foetus had three other pregnancies: a male with a balanced translocation, and two foetuses with 1p36.3-pter monosomy and 6q25.2-qter trisomy.
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PMID:Cryptic 1p36.3/6q25.2 translocation in three generations ascertained through a foetus with IUGR and cerebral malformations. 1455 26

During the last few years there has been an increasing number of reports of chromosomal abnormalities identified by subtelomeric fluorescence in situ hybridization testing in children with unexplained mental retardation. As more children are identified with subtelomeric deletions, duplications, and cryptic unbalanced rearrangements by this testing, questions have arisen regarding the appropriate use of this new technology. A review of current knowledge regarding the clinical phenotypes seen in these patients as well as of newer information regarding the use of this new cytogenetic test in areas outside clinical genetics may help to determine which patients would benefit from its use.
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PMID:Use of subtelomeric fluorescence in situ hybridization in cytogenetic diagnosis. 1463 Dec 5

Constitutional de novo complex chromosomal rearrangements (CCRs) are a rare finding in patients with mild to severe mental retardation. CCRs pose a challenge to the clinical cytogeneticist: generally CCRs are assumed to be the cause of the observed phenotypic abnormalities, but the complex nature of these chromosomal changes often hamper the accurate delineation of the chromosomal breakpoints and the identification of possible imbalances. In a first step towards a more detailed molecular cytogenetic characterization of CCRs, we studied four de novo CCRs using multicolor fluorescent in situ hybridization (M-FISH), comparative genomic hybridization (CGH), and FISH with region specific probes. These methods allowed a more refined characterization of the breakpoints in three of the four CCRs. The occurrence of 7q breakpoints in three out of these four CCRs and in 30% of reported CCRs suggested preferential involvement of this chromosomal region in the formation of CCRs. Further analysis of these 7q breakpoints revealed a 2 Mb deletion at 7q21.11 in one patient and involvement of the same region in a cryptic insertion in a second patient. This particular region contains at least 5 candidate genes for mental retardation. The other patient had a breakpoint more proximal to this region. The present data together with these from the literature provide evidence that a region within 7q21.11 may be prone to breakage and formation of CCRs.
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PMID:Molecular cytogenetic analysis of complex chromosomal rearrangements in patients with mental retardation and congenital malformations: delineation of 7q21.11 breakpoints. 1467 81

Chromosome anomalies are responsible for a significant proportion of patients with mental retardation, and congenital anomalies. Development of new molecular cytogenetic techniques has provided a powerful tool for detection of patients with subtle chromosome abnormalities. Particularly, investigation of the gene-rich subtelomeric regions has generated interest regarding the implications and prevalence of cryptic chromosomal rearrangements. Here we describe an adult with a submicroscopic deletion of 18pter, detected by subtelomeric FISH probe. The patient is a 42-year-old man with a history of developmental delay, moderate mental retardation, and symptoms of paranoid schizophrenia since adolescence. His physical examination is remarkable for only a few dysmorphic findings typically seen in 18p- syndrome (round face, hypertelorism, down-slanted palpebral fissures, temporal narrowing, small hands and feet). He lacks significant short stature, skin changes, and associated anomalies involving internal organs. All known patients with deletions of the short arm of chromosome 18 have either loss of large parts of 18p or of the entire p-arm, or have complex chromosomal rearrangement involving other chromosomes. To our knowledge, this is the first description of a cryptic subtelomeric deletion of 18p and the first case of such a chromosomal anomaly in a patient with schizophrenia. Small subtelomeric chromosomal deletions would be missed by standard G-banded karyotyping. Therefore, FISH analysis using subtelomeric probes should be considered for diagnostic evaluation of patients with psychiatric symptoms and mental retardation in whom the karyotype is normal.
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PMID:Subtelomeric deletion of 18p in an adult with paranoid schizophrenia and mental retardation. 1470 8

Submicroscopic rearrangements involving chromosome ends are responsible for the unexplained mental retardation and multiple congenital anomalies observed in a number of patients. We have studied a patient with mental retardation, significant microcephaly, alopecia universalis, and other anomalies who carries an unbalanced segregant from a cryptic reciprocal translocation involving chromosomes 9 and 19. FISH studies using subtelomere specific probes revealed a derivative chromosome 9 in which the 9q subtelomeric sequence has been replaced by 19p subtelomeric sequence. As a result, the patient has partial monosomy 9q and partial trisomy 19p. The patient inherited the derivative 9 from his father, who carries a cryptic apparently balanced reciprocal translocation involving the terminal regions of 9q and 19p. This case is exceptional in that reports of rearrangements involving distal chromosome 9q and 19p are rare. This study demonstrates the utility of subtelomere specific FISH probes for detecting cryptic subtelomeric rearrangements in patients with idiopathic mental retardation and normal appearing karyotypes.
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PMID:Submicroscopic deletion 9(q34.3) and duplication 19(p13.3): identified by subtelomere specific FISH probes. 1475 69

The use of subtelomeric FISH probes has greatly supplemented conventional chromosome analysis in detecting cryptic anomalies in patients with mental retardation (MR), dysmorphic features, and congenital malformations. We report a 3-month-old boy who was diagnosed with ambiguous genitalia, dysmorphic features, and developmental delay. Standard chromosome studies on blood revealed a chimeric karyotype of 46,XY,t(4;5)(q31.1;q14)[46]/46,XX[4]. The boy had intra-abdominal gonads that were testicular in origin by biopsy. Multiple dysmorphic features, marked hypotonia, developmental delay, poor growth, and relative macrocephaly were noted on physical exam. His 2.5-year-old sister also presented with hypotonia, developmental delay, relative macrocephaly, and similar dysmorphic stigmata. In addition, she was diagnosed with several internal malformations. Her karyotype was 46,XX. Due to the striking phenotypic similarity, subtelomeric FISH studies were initiated in the siblings. In addition to the known balanced karyotypic abnormalities, the boy was found to have a derivative chromosome 5 with a 5pter deletion and a 17pter duplication. This cryptic abnormality was also detected in his sister. Chromosome analysis of the father revealed a subtle balanced t(5;17)(p15.31;p13.1) which was confirmed by subtelomeric FISH, whereas the mother's chromosome complement was normal. This familial constellation illustrates the usefulness of subtelomeric FISH in the diagnosis of cryptic chromosome abnormalities in patients for whom conventional karyotype does not disclose findings sufficient to explain the observed phenotypic anomalies.
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PMID:Unbalanced cryptic 5p deletion/17p duplication identified by subtelomeric FISH in a family with a boy with chimerism and a balanced t(4;5). 1475 72

Mental retardation affects 1-3% of the general population, and the genetic causes in many cases are unknown. Cytogenetically undetected chromosomal imbalances have been indicated as an explanation. Nowadays, due to the development of molecular cytogenetic techniques, it is possible to identify cryptic rearrangements involving the ends of chromosomes. We report a screening using chromosome-specific telomere fluorescence in-situ hybridization (FISH) probes, in a group of 30 patients with a well-characterized phenotype including mental retardation, dysmorphic features, and a normal karyotype. Among them, two subtelomeric rearrangements have been detected and characterized. One of them is a de novo deletion of 1p36, which has been previously described as a new contiguous gene syndrome. The second is an unbalanced product of a cryptic translocation involving chromosomes 1 and 13, which results in a partial 1q trisomy and partial 13q monosomy. These findings highlight, the importance of searching for cryptic subtelomeric rearrangements in non-syndromic mentally retarded patients.
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PMID:Cryptic chromosomal rearrangement screening in 30 patients with mental retardation and dysmorphic features. 1503 70

We described three unrelated children with cryptic 9q34.3 rearrangements and similar clinical manifestations: two with 9q34.3 terminal deletions and the other with an unbalanced translocation involving 9q34.3-qter monosomy and 6p25-pter trisomy. Common features among the three we studied and the other six patients with 9q34.3 deletions in the literature include microcephaly, mental retardation (MR), hypotonic, and epileptic seizures. Their facial characteristics included flat face, arched eyebrows, synophrys, hypertelorism, short nose, anteverted nostrils, carp mouth, protruding tongue, micrognathia, and pointed chin. Other frequent abnormalities were cardiac abnormalities, cryptorchidism or hypospadias, and abnormal toes. These findings are characteristic enough to be a clinically recognizable syndrome.
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PMID:9q34.3 deletion syndrome in three unrelated children. 1505 42

In a prospective study 94 individuals with mental retardation (MR) and dysmorphic features with normal conventional karyotypes were investigated by both subtelomeric FISH and high resolution CGH (HR-CGH) in order to compare the potential of the two techniques in this application. A total of 9.6% abnormalities were found with HR-CGH and subtelomeric FISH, with HR-CGH detecting 8.5% (95% CI: 4.4-15.9) and FISH 3.2% (95% CI: 1.2-9.0). Thus, the techniques complemented each other, however, the diagnostic yield appeared higher of HR-CGH than of subtelomeric FISH, as most aberrations were interstitial. Another 330 individuals with MR and dysmorphic features with normal conventional karyotypes were investigated by HR-CGH on a routine basis. When added to the analyses of the prospective study a total of 51/424 (12%; 95% CI: 9.3-15.5) abnormalities were found, of which the majority were interstitial. We conclude that HR-CGH is well suited for routine screening for cryptic chromosomal imbalances in patients with MR and dysmorphic features. It is likely that the use of the technique in this application will reinforce the effort of defining new syndromes.
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PMID:Prospective study comparing HR-CGH and subtelomeric FISH for investigation of individuals with mental retardation and dysmorphic features and an update of a study using only HR-CGH. 1510 96

Extra structurally abnormal chromosomes (ESACs) and cryptic rearrangements are often associated with mental retardation and phenotypic abnormalities. In some cases their characterisation, using standard cytogenetic techniques and fluorescence in situ hybridization (FISH), is difficult and time consuming, where a fast and accurate identification is essential, especially when such chromosomal aberrations are found in prenatal diagnosis. A recent molecular technique, spectral karyotyping (SKY), based on the spectral signature of 24 chromosome-specific painting probes labelled with different combinations of five fluorochromes, allows the simultaneous visualisation of all human chromosomes in different colours. We used SKY analysis on 14 cases with rare ESACs or cryptic unbalanced rearrangements found at pre- or postnatal diagnosis. SKY analysis permitted the classification of chromosome rearrangements in all 14 cases analysed in combination with FISH analysis.
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PMID:Identification of 14 rare marker chromosomes and derivatives by spectral karyotyping in prenatal and postnatal diagnosis. 1510 1


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