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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 (MR) is a frequent manifestation in patients referred to departments of medical genetics (OLG). At the OLG in Martin their number in the years 1981-1985 was 324, i.e. 21.22% of the total number of examined subjects. MR was found as one of the pathological symptoms (symptomatic MR) in 86.73% and as the only pathological manifestation (isolated MR) in 13.27%. Genetic factors were revealed in 59%, exogenous ones in 19%, and in 22% the aetiology was not unequivocally resolved. As to genetic factors, the most frequent cause were chromosomal aberrations (in 104 patients-53%), a monogenic character was found in 68 subjects (35%) and a multifactorial one in 24 (12%). As to chromosomal aberrations, in 102 cases autosomes were affected (91 times numerical and 11 times structural affection), in four subjects a numerical anomaly of genosomes was involved and once a combined aberration of an autosomal and gonosomal character. The authors give the character and number of different types of aberrations and the incidence of so-called chromosomal markers (12 cases) and they evaluate their causal relationship with MR. Further advances in the aetiological evaluation of genetic factors will be made possible by the introduction of strip methods with a high resolution technique (use of prophasic chromosomes), combined with hybridization in situ, cytogenetic methods for the detection of individuals with the fragile X-chromosome syndrome, and in particular the application of the technology of recombinant DNA for the diagnosis of clinical and genetic units at the gene level.
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PMID:[Chromosome aberrations in a group of mentally retarded persons]. 252 54

Fragile-X mental retardation (FRAX-MR) is one of the more common X-linked disorders affecting 1 in 1,500 newborn males. This disease is characterized by the expression of fragile site in the region q27.3 of the X-chromosome of affected boys when their lymphocytes are cultured in folate deficient medium. In most patients there is macroorchidism postpubertally. The clinical diagnosis of carrier females based on the expression of fragile site in Xq27.3 is usually difficult and sometimes impossible. About half of the carrier females escape diagnosis by this method. Furthermore, prenatal diagnosis is not always feasible. Using Restriction Fragment Length Polymorphism (RFLP) and cloned DNA segments from the region Xq27-Xqter as probes, we have investigated Swedish families with FRAX-MR in three generations. Interesting observations, previously unreported to our knowledge, have been made in some patients and carrier mothers, using one of the probes which is localized to the distal end of Xq. The significance of these findings and the linkage of the disease locus to the different probes used in this study is presented.
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PMID:Analysis of fragile X-mental retardation families using flanking polymorphic DNA probes. 287 49

Deficiency of ornithine transcarbamylase (OTC; EC 2.1.3.3), a hepatic mitochondrial enzyme involved in the detoxification of ammonia, is a severe inborn error of metabolism. It is an X-linked disorder which results characteristically in ammonia intoxication, protein intolerance and mental retardation. Early death of affected hemizygous male infants is common, while clinical manifestations in heterozygous females are variable due to random X-chromosome inactivation. Prenatal diagnosis by amniocentesis has not been feasible because OTC is not expressed in amniocytes and because no unusual metabolites can be detected in amniotic fluid. Fetal liver biopsy has been performed for some families at risk, but the dangers inherent in this procedure severely limit its usefulness. In this report, we describe the use of a nearly full-length cloned human cDNA to begin to characterize normal and mutant human OTC genes. One of 15 affected males was found to have a partial deletion of the OTC gene. Two distinct restriction fragment length polymorphisms (RFLPs) were identified at the OTC locus using the restriction endonuclease MspI; 69% of women tested were heterozygous for one or both polymorphisms. Identification of these common polymorphisms makes it possible to offer prenatal diagnosis to a large fraction of obligate carriers and to provide information on carrier status to some females at risk.
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PMID:Gene deletion and restriction fragment length polymorphisms at the human ornithine transcarbamylase locus. 298 25

We present a dysmorphic syndrome in eight males of the same family (four brothers, three cousins and one uncle) that is characterised by: mental retardation, facial dysmorphia, abnormal growth of teeth, skin dimple at the lower back, clinodactyly, patella luxation, malformation of lower limbs, abnormalities of the fundus of the eye and subcortical cerebral atrophy. These physical defects do not correspond to any previously described syndrome, which suggests that it is a new syndrome. According to the model of heredity this syndrome could be due to a mutant gene situated in the X-chromosome.
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PMID:X-linked dysmorphic syndrome with mental retardation. 312 Dec 20

Female heterozygotes of the fra(X) form of mental retardation show variable degrees of mental impairment and phenotype expression of the disorder. This might be an effect of inactivation of the X-chromosome which carries the fra(X)(q). Prior replication studies in heterozygous carriers gave contradictory results with respect to possible genotype-phenotype correlation. In the interpretation of these studies it is important to understand the effect of BrdU on the fra(X)(q) expression. In a group of 13 hemizygous patients with fra(X)(q) and 7 heterozygous carriers we studied the effect of BrdU on fra(X) expression. In the heterozygous carriers the use of BrdU resulted in a significant suppression of the fra(X)(q), while in hemizygous patients no difference in fra(X)(q) frequency with or without BrdU could be observed. It can be concluded that BrdU suppresses the fra(X)(q) preferentially on the inactive X-chromosome. Thus the fra(X)(q) frequency on the active X-chromosome is of primary importance in phenotype correlation studies among heterozygous carriers. In our group of heterozygous carriers we observed a negative correlation between (IQ) phenotype and fra(X)(q) expression on the active X-chromosome. This suggests that the gene for the fra(X)(q) form of mental retardation is on the X-chromosome and undergoes inactivation.
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PMID:Fra(X) frequency on the active X-chromosome and phenotype in heterozygous carriers of the fra(X) form of mental retardation. 317 61

An analysis of the linkage of a non-syndromal form of X-linked mental retardation (MRX1) with a number of markers on the X chromosome was performed in a large pedigree. The affected males had moderate mental retardation; in all other clinical respects and cytogenetically they were normal. No recombinants were observed between the MRX1 gene and the marker DXS14 (p58.1) located at Xp11-cen (Z (max.) = 2.12 at theta = 0.00). Recombination was observed between the MRX1 gene and the markers DXS7 and DXYS1 which flank DXS14. This form of XLMR maps to the centromeric portion of the X-chromosome.
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PMID:A non-syndromal form of X-linked mental retardation (XLMR) is linked to DXS14. 317 66

The X-chromosome was studied in blood lymphocytes of 68 males with aspecific mental retardation (MR), their 57 relatives and 15 intellectually normal males. The incidence of a fragile X-chromosome (fra(X)) was found to be 4.7% in an unselected group of 42 patients, 50% among 10 probands in which pedigree data were suggestive of X-linked MR diagnosis, and 75% in the group of 15 patients selected for phenotype characteristic of the fragile X syndrome. The fra(X) was present in 1-43% of metaphases in different individuals, no such marker being observed in cells of 15 normal individuals. No significant difference was found when the incidence of the fra(X) was compared in cells cultured in the medium 199 with low folic acid content and the Eagle's medium supplemented with 5-fluorodeoxyuridine (10.62 +/- 2.94 SEM and 13.53 +/- 2.85 SEM, respectively). The possibility of false-positive diagnosis of the fragile X syndrome was quantitatively appreciated. A half of the patients showing a fra(C) in conventionally stained chromosomes were found to have fragile 6 autosome as the only marker in these cells, and in patients with the evident fragile (X) syndrome the fra(6) constituted about one-third of the fra(X) frequency. Both culture media employed were similar in the fra(6) induction.
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PMID:[Chromosomal characteristics of X-linked recessive mental retardation. I. The X chromosome]. 346 Sep 28

An Indiana family segregating a syndrome of X-linked mental retardation and skeletal anomalies was tested for linkage of the mutant gene to X-chromosome molecular markers. Lod scores of 3.27 and 3.06 (theta = 0) for the molecular probes St14-1 (DXS52) and Dx13 (DXS15), respectively, indicate that the disease gene is located in the terminal portion of Xq.
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PMID:Localization of the gene for a syndrome of X-linked skeletal dysplasia and mental retardation to Xq27-qter. 346 36

Choroideremia, an X-chromosome linked retinal dystrophy of unknown pathogenesis, causes progressive nightblindness and eventual central blindness in affected males by the third to fourth decade of life. Choroideremia has been mapped to Xq13-21 by tight linkage to restriction fragment length polymorphism loci. We have recently identified two families in which choroideremia is inherited with mental retardation and deafness. In family XL-62, an interstitial deletion in Xq21 is visible by cytogenetic analysis and two linked anonymous DNA markers, DXYS1 and DXS72, are deleted. In the second family, XL-45, an interstitial deletion was suspected on phenotypic grounds but could not be confirmed by high-resolution cytogenetic analysis. We used phenol-enhanced reassociation of 48,XXXX DNA in competition with excess XL-45 DNA to generate a library of cloned DNA enriched for sequences that might be deleted in XL-45. Two of the first 83 sequences characterized from the library were found to be deleted in probands from family XL-45 as well as from family XL-62. Isolation of these sequences proves that XL-45 does contain a submicroscopic deletion and provides a starting point for identifying overlapping genomic sequences that span the XL-45 deletion. Each overlapping sequence will be studied to identify exons from the choroideremia locus.
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PMID:Isolation of anonymous DNA sequences from within a submicroscopic X chromosomal deletion in a patient with choroideremia, deafness, and mental retardation. 347 58

The author studied the prevalence of severe mental retardation in Vilnyus and considered the status of its etiological and clinical differentiation. A total of 224 cases of oligophrenia were identified among children aged 4-13 years which constituted a populational rate of 0.31% in the above age group. A marked predominance of males among the cases with undifferentiated forms was ascertained, which is probably due to the accumulation in this group of X-chromosome-linked mental retardation. Cytogenetic examination of 20 suspected cases revealed the syndrome of a fragile X chromosome in 4 patients.
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PMID:[Severe mental retardation in an urban child population]. 357 30


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