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

Mental retardation occurs in 2-3% of the general population either in isolation or in combination with facial dysmorphism and/or malformations. Chromosomal abnormalities are a most common etiology. Karyotype displays chromosome aberrations in about 10% of patients but it has a limited resolution (5 Mb). Recently, the development of new molecular cytogenetic tools, especially array CGH, allowed to detect smaller abnormalities and increased the diagnosis capability of 15-20%. Among these newly detected rearrangements, some of them are recurrent and define new recognized syndromes. We will first briefly explain the non-allelic homologous recombination (NAHR) mechanism that underlines the origin of recurrent microdeletions and microduplications. Then we will describe eight new syndromes, four microdeletions (del 17q21.31, del 3q29, del 15q24, del 2q32.3q33) and four microduplications (dup 22q11.2, dup 7q11.23, dup 17p11.2, duplication of MECP2). A better knowledge of these new recurrent chromosomal syndromes will allow to improve care for patients, to develop targeted chromosomal diagnosis and to identify genes involved in neurocognitive functions.
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PMID:[New chromosomal syndromes]. 1846 39

Array comparative genomic hybridization (array CGH) has revolutionized the cytogenetic testing available for patients with learning disabilities who have "chromosomal" phenotypes with dysmorphic features and multiple anomalies. Screening large patient cohorts with mental retardation by array CGH has recently lead to the characterization of many novel microdeletion and microduplication syndromes, initially according to the shared cytogenetic aberrations, with secondary characterization of the corresponding phenotypes. This review provides a detailed clinical and molecular cytogenetic description of several of the most common of these aberrations. We have chosen to focus on patients in whom the cytogenetic abnormalities were principally described by array CGH, rather than by G-banded karyotyping or fluorescence in-situ hybridization. The syndromes that we have chosen include the 17q21.31 deletion and 17q21.31 duplication syndromes, 15q13.3 deletion syndrome, 16p11.2 deletion syndrome, 15q24 deletion syndrome, 1q41q42 deletion syndrome, 2p15p16.1 deletion syndrome and 9q22.3 deletion syndrome. In time, we hypothesize that at least some of these will become as clinically well characterized and recognizable to the clinician as the commoner microdeletion syndromes today. Although the full extent of the phenotypes is still evolving for many of these novel microdeletions, it is clear that array CGH has heralded an unparalleled era of discovery for clinical cytogenetics.
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PMID:Novel microdeletion syndromes detected by chromosome microarrays. 1851 78

OPHN1 mutations cause a syndromic form of mental retardation (MR) characterized by cerebellar hypoplasia, early hypotonia, motor and speech delay, with occasional seizures and strabismus. Here we report on a familial chromosome duplication spanning about 800 Kb of Xq12q13.1, associated with MR and a distinctive phenotype in the affected male, but not in his heterozygous mother. The parents were healthy and non-consanguineous with a history of three pregnancies. The first resulted in the birth of a boy with MR, motor impairment and seizures. The second pregnancy was terminated because of trisomy 18. At the time of the third, the first affected boy was analyzed by array-CGH, which revealed a 800 Kb duplication at Xq12q13.1, encompassing three genes, including OPHN1. This mutation was inherited from his healthy mother and was not present in any of the three maternal brothers. To our knowledge this is the first report of a clinical phenotype associated with duplication of Xq12q13.
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PMID:Association of syndromic mental retardation with an Xq12q13.1 duplication encompassing the oligophrenin 1 gene. 1851 29

Genosensor Array 300 (Abbott) is a multiplex platform for array-based comparative genomic hybridization that detects unbalanced genomic aberrations including whole chromosome gains/losses, microdeletions, duplications and unbalanced subtelomeric rearrangements. A series of 30 patients with unexplained mental retardation, dysmorphic features, congenital abnormalities and normal high resolution karyotype and FISH subtelomeric studies were analyzed using Genosensor Array 300 array-CGH. We identified a chromosomal aberration in one patient with an interstitial 1p31.1 deletion. FISH analysis with BACs specific probes of the 1p region confirmed the interstitial 1p22.2-p31.1 deletion. The patient was a 20-year-old man with short stature, facial dysmorphism including asymmetry, scoliosis, severe psychomotor delay and an epibulbar dermoid cyst. The phenotype was compatible with Goldenhar syndrome despite the absence of asymmetric ears. This observation is of interest since it could be a clue in the search for the genes responsible for Goldenhar syndrome. This study demonstrates the utility of the array-CGH technology in detecting interstitial deletions.
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PMID:Array-CGH in a series of 30 patients with mental retardation, dysmorphic features, and congenital malformations detected an interstitial 1p22.2-p31.1 deletion in a patient with features overlapping the Goldenhar syndrome. 1862 84

Subtelomeric imbalances are a significant cause of congenital disorders. Screening for these abnormalities has traditionally utilized GTG-banding analysis, fluorescence in situ hybridization (FISH) assays, and multiplex ligation-dependent probe amplification. Microarray-based comparative genomic hybridization (array-CGH) is a relatively new technology that can identify microscopic and submicroscopic chromosomal imbalances. It has been proposed that an array with extended coverage at subtelomeric regions could characterize subtelomeric aberrations more efficiently in a single experiment. The targeted arrays for chromosome microarray analysis (CMA), developed by Baylor College of Medicine, have on average 12 BAC/PAC clones covering 10 Mb of each of the 41 subtelomeric regions. We screened 5,380 consecutive clinical patients using CMA. The most common reasons for referral included developmental delay (DD), and/or mental retardation (MR), dysmorphic features (DF), multiple congenital anomalies (MCA), seizure disorders (SD), and autistic, or other behavioral abnormalities. We found pathogenic rearrangements at subtelomeric regions in 236 patients (4.4%). Among these patients, 103 had a deletion, 58 had a duplication, 44 had an unbalanced translocation, and 31 had a complex rearrangement. The detection rates varied among patients with a normal karyotype analysis (2.98%), with an abnormal karyotype analysis (43.4%), and with an unavailable or no karyotype analysis (3.16%). Six patients out of 278 with a prior normal subtelomere-FISH analysis showed an abnormality including an interstitial deletion, two terminal deletions, two interstitial duplications, and a terminal duplication. In conclusion, genomic imbalances at subtelomeric regions contribute significantly to congenital disorders. Targeted array-CGH with extended coverage (up to 10 Mb) of subtelomeric regions will enhance the detection of subtelomeric imbalances, especially for submicroscopic imbalances.
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PMID:Identification of chromosome abnormalities in subtelomeric regions by microarray analysis: a study of 5,380 cases. 1866 43

Pericentric inversions of chromosome 19 are very rare rearrangements. Only one case was shown to have resulted in duplication deficiency in the offspring. We report a familial case of pericentric inversion of chromosome 19 not detectable by standard karyotype and usual subtelomeric FISH probes. This inversion was transmitted in its balanced and in its recombinant form to the offspring. The two children carrying the recombinant chromosome 19 presented with growth and mental retardation, microcephaly, mild facial dysmorphism and clinodactyly. The recombinant chromosome 19 was characterized by FISH and array CGH. It consisted of a 400kb 19pter deletion and a 6.9Mb (19q13.33-qter) duplication. This observation supports the recombination risk of pericentric inversion of chromosome 19 and emphasizes the role of molecular cytogenetics techniques in the characterization of chromosome 19 rearrangements.
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PMID:Monosomy 19pter and trisomy 19q13-qter in two siblings arising from a maternal pericentric inversion: clinical data and molecular characterization. 1867 48

We report on a 25-year-old male with mental retardation and global developmental delay, low levels of total and LDL cholesterol and dysmorphism, which includes macrocephaly, hypertelorism, synophrys, telecanthus, prominent philtrum, low set ears, bilateral cataracts, bilateral cleft lip with cleft palate and widely spaced nipples. While his karyotype and subtelomeric FISH studies were normal, a de novo, 5.4 Mb interstitial deletion at 1p32 [del(1)(p32.2-p32.3)] was identified by oligonucleotide aCGH. The deleted region encompasses a cluster of genes involved in fatty acid oxidation and cholesterol metabolism. One of these genes is PCSK9, a key regulator for a number of cell-surface LDL receptors. In addition to the loss of the paternal allele, our patient is hemizygous for the A443T weak loss-of-function mutation in exon 8 of PCSK9. Loss-of-function mutations within PCSK9 have been shown to cause hypocholesterolemia. Another gene also mapped to this region and deleted in this patient is DAB1, reported to be involved in brain development. Based on the findings in the current patient and in the four previously reported individuals with del(1)(p32.2-p32.3), we suggest that these patients may have a new microdeletion syndrome that may have gone undetected because of its location in a G-negative band. However, the condition can easily be identified by array-CGH.
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PMID:Deletion (1)(p32.2-p32.3) detected by array-CGH in a patient with developmental delay/mental retardation, dysmorphic features and low cholesterol: A new microdeletion syndrome? 1868 Jan 92

We report on a 16-year-old girl with a multiple congenital anomalies/mental retardation condition, in which a 1.7 Mb tandem duplication of chromosome region 16p13.3 was detected by array-CGH. Mental retardation was moderate (IQ 45), with very limited speech. She had tall stature with relative microcephaly. Clinical manifestations included distinctive facial appearance with deep set eyes, narrow palpebral fissures, wide nasal bridge, long philtrum, rounded nasal tip, thin upper lip, protruding mandible and abnormal auricles, hand and foot anomalies. The causal 16p13.3 duplication is one of the smallest reported so far, and includes the CBP gene, whose haploinsufficiency is responsible for the Rubinstein-Taybi syndrome. By comparing clinical manifestations of our patient with those of patients carrying similar rearrangements, we could infer that 16p13.3 microduplications encompassing the Rubinstein-Taybi region result in a recognizable clinical condition, most likely representing a single gene disorder.
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PMID:Duplication of the Rubinstein-Taybi region on 16p13.3 is associated with a distinctive phenotype. 1868 73

Recent advances in molecular cytogenetics enable identification of small chromosomal aberrations that are undetectable by routine chromosome banding in 5-20% of patients with mental retardation/developmental delay (MR/DD) and dysmorphism. The aim of this study was to compare the clinical usefulness of two molecular cytogenetic techniques, metaphase high-resolution comparative genomic hybridization (HR-CGH) and targeted array CGH, also known as Chromosomal Microarray Analysis (CMA). A total of 116 patients with unexplained mild to severe MR and other features suggestive of a chromosomal abnormality with apparently normal or balanced karyotypes were analyzed using HR-CGH (43 patients) and/or CMA (91 patients). Metaphase HR-CGH detected seven interstitial deletions (16.3%). Rare deletions of chromosomes 16 (16p11.2p12.1) and 8 (8q21.11q21.2) were identified. Targeted CMA revealed copy-number changes in 19 of 91 patients (20.8%), among which 11 (11.8%) were clinically relevant, 6 (6.5%) were interpreted as polymorphic variants and 2 (2.1%) were of uncertain significance. The changes varied in size from 0.5 to 12.9 Mb. In summary, our results show that metaphase HR-CGH and array CGH techniques have become important components in cytogenetic diagnostics, particularly for detecting cryptic constitutional chromosome imbalances in patients with MR, in whom the underlying genetic defect is unknown. Additionally, application of both methods together increased the detection rates of genomic imbalances in the tested groups.
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PMID:Application of metaphase HR-CGH and targeted Chromosomal Microarray Analyses to genomic characterization of 116 patients with mental retardation and dysmorphic features. 1869 22

Clinical manifestations of Jacobsen syndrome (JBS) depend on the size of the 11qter deletion, which usually varies between approximately 7 and 20 Mb. Typical JBS features include developmental delay/mental retardation, short stature, congenital heart defects, thrombocytopenia, and characteristic dysmorphic facial features. We report on a family in which a 4-year-old girl as well as her mother and maternal uncle present with subtle features of JBS. Notably, neither thrombocytopenia nor congenital anomalies were detected in this family. Cytogenetic analyses revealed normal karyotypes. Using fluorescence in situ hybridization (FISH) and whole-genome oligonucleotide array CGH analyses, we identified an approximately 5 Mb deletion of the terminal part of chromosome 11q in all the three affected family members. The deletion breakpoint was mapped between 129,511,419 and 129,519,794 bp. This is the smallest deletion reported in a JBS patient. Interestingly, the FLI1 (friend leukemia virus integration 1) hematopoiesis factor gene located approximately 6.5 Mb from 11qter and usually deleted in patients with JBS, is intact. Our data support previous hypotheses that FLI1 haploinsufficiency is responsible for thrombocytopenia in patients with JBS.
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PMID:Clinical and molecular-cytogenetic evaluation of a family with partial Jacobsen syndrome without thrombocytopenia caused by an approximately 5 Mb deletion del(11)(q24.3). 1879 74


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