Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0917816 (mental retardation)
 15,867 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The most common genetic cause of mental retardation after Down's syndrome, the fragile X syndrome, is associated with the occurrence of a fragile site at Xq27.3. This X-linked disease is intriguing because transmission can occur through phenotypically normal males. Theories to explain this unusual phenomenon include genomic rearrangements and methylation changes associated with a local block of reactivation of the X chromosome. Using microdissected markers close to the fragile site, we have been able to test these hypotheses. We present evidence for the association of methylation with the expression of the disease. However, there is no simple relationship between the degree of methylation and either the level of expression of the fragile site or the severity of the clinical phenotype.
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PMID:Physical mapping across the fragile X: hypermethylation and clinical expression of the fragile X syndrome. 199 11

Two cases of a very unusual bone dysplasia in two brothers are reported. Features included very severe dwarfism, with macrocrania and mental deficiency. Roentgenograms taken in early infancy were reminiscent of spondyloepiphyseal dysplasia congenital syndrome but the course was not suggestive of this diagnosis. The shafts of the long bones became increasingly narrow, whereas the metaphyses broadened and the epiphyses at the knee became extremely wide. Vertebral bodies were ovoid or trapezoidal. The skull was extremely large. Since two offspring of consanguineous parents were involved, this disease is certainly of genetic origin. Autosomal recessive transmission is likely, although X-linked transmission cannot be outruled.
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PMID:[Chondrodysplasia with macrocranium and mental retardation in 2 brothers]. 200 33

We have identified 39 X-linked conditions in which mental retardation seems to be the primary characteristic, although pathogenesis is unknown. These conditions can be subdivided into syndromal and non-syndromal, depending on the existence of a recognizable pattern of minor anomalies and/or malformations, or lack thereof. Seventeen genes have been regionally mapped onto the X chromosome. However, in 14 instances the data were derived from a single family and most lod scores were less than 3.0.
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PMID:XLMR genes: update 1990. 201 56

Photographs of normal and abnormal relatives with X-linked mental retardation (XLMR) and clinical data are combined in a Macintosh II computer system to provide an objective and versatile means of evaluating developmental abnormalities. The system includes a flatbed scanner for the entry of photographs and text, additional memory to enhance resolution of photographs, and several programs which facilitate searches for keywords. The primary advantages of the system include an easy interaction between descriptive words and photographs, and rapid comparison of whole faces and specific traits from many individuals. Information within families and between disorders can easily be compared in coded or uncoded fashion. Data from the 34 currently described syndromes emerging from the category of "non-specific XLMR" are being used to develop and test this approach. Neither standard photographs nor most computerized diagnostic systems permit this flexibility. Ultimately, this approach will provide a valuable diagnostic and teaching aid.
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PMID:Computerized approach to X-linked mental retardation syndromes. 201 57

We report on a 4 generation family of individuals with an X-linked form of mental retardation involving 9 affected males and 5 obligate carrier females. Key manifestations include severe mental retardation, early hypotonia with progression to spasticity and contractures, choreoathetosis, seizures, presence of a long, narrow face with coarse features, cystic enlargement of the fourth ventricle with cerebellar hypoplasia (Dandy-Walker malformation), and iron accumulation in the basal ganglia with neuroaxonal dystrophy similar to Hallervorden-Spatz disease. Of the 5 known heterozygotes, 3 are dull intellectually, and one of the 3 developed a "presenile dementia." At autopsy she had iron deposition and neuroaxonal dystrophy in the basal ganglia and atrophy of the cerebral cortex. Although the clinical findings among relatives are variable, we conclude that this is a distinct, previously unrecognized X-linked mental retardation syndrome.
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PMID:New X-linked mental retardation disorder with Dandy-Walker malformation, basal ganglia disease, and seizures. 201 58

We describe a family with two half-brothers affected with severe mental retardation. The phenotype in the affected individuals is characterized by apparent acromegaly, profound mental retardation, and hyperactivity. The mother has analogous but less severe facial anomalies and mild mental impairment. Screening for fra(X) (q) was negative in peripheral lymphocytes using methotrexate for fra(X) enhancement. The clinical findings in our patients are similar to those described by Fryns et al. [1986] in two patients with acquired lesions of the central nervous system. CT investigations in one of our patients showed areas of hyperdensity in the pontine region and a small subarachnoid cyst. The pedigree suggests X-linked inheritance. The association of apparent acromegaly, CNS anomalies, megalotestes, and mental retardation in this family supports the hypothesis that a distinct syndrome may exist with phenotype anomalies more severe than those characteristic for the Martin-Bell syndrome but without fragile X.
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PMID:Mental retardation, acromegalic face, and megalotestes in two half-brothers: a specific form of X-linked mental retardation without fra(X) (q)? 201 59

We studied 10 members of a 4 generation Missouri kindred with a dominant mental retardation syndrome with increasing severity in males. The 21 year-old propositus presented with severe mental retardation, microcephaly, asymmetric face, exotropia, hypogonadism, joint hypermobility, rocker bottom feet, and 10 low digital arches. Two brothers and a male cousin had similar features. The mother, sister, niece, maternal aunt, female cousin, and grandmother were examined and each had 8 to 10 low digital arches. Five of the women had exotropia and one had pes cavus feet. Chromosome analysis for fragile X in multiple relatives was normal. To determine the likelihood that this was an X-linked syndrome. DNA from relatives was hybridized to probes which detect 13 different loci spanning the X-chromosome. A peak LOD score of 2.78 at theta equal to 0.0 was calculated for the syndrome locus and DXYS1 (pDP34). The more distal Xq loci showed increasing recombination with the syndrome locus. These results are consistent with location for this syndrome near Xq21.31, the chromosomal locus for DXYSI.
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PMID:Unique X-linked mental retardation syndrome with fingertip arches and contractures linked to Xq21.31. 201 61

Linkage analysis was carried out in a large four-generation German family segregating for non-specific X-linked mental retardation. Affected males have moderate intellectual handicap. Speech delay, deviant behaviour, and hyperactivity have also been reported. Head circumference and testicular volumes are normal. Cytogenetic analysis failed to show evidence for fragile site or structural abnormality of the X chromosome. None of the obligatory carriers shows any clinical symptoms. Close linkage without recombination (lod scores 1.74 to 2.05) has been found between the disease locus (MRX1) and the polymorphic DNA loci DXS7 (Xp11.4-p11.3), MAOA (Xp11.3-p11.23), DXS255 (Xp11.22), and DXS159 (Xq12) suggesting that the gene responsible for the disease in this family maps in the pericentromeric region of the X chromosome. Linkage data obtained with the flanking marker loci OTC (Xp21.1) and DXS95 (Xq21.2-q21.3) also were compatible with this localization of the MRX1 gene. Close linkage to loci from Xp22, Xq22, Xq24-25, or Xq28 could be excluded.
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PMID:Gene for non-specific X-linked mental retardation maps in the pericentromeric region. 201 62

We report on 4 new cases of mildly retarded patients with marfanoid habitus and a characteristic constellation of minor anomalies. These patients, although sporadic, are likely to be affected by the same X-linked type of mental retardation described by Lujan et al. (American Journal of Medical Genetics 17:311-322, 1984) and more recently by Fryns and Buttiens (American Journal of Medical Genetics 28:267-274, 1987). The similar psychiatric history in 2 of our patients suggests that psychotic behaviour could be an additional manifestation, previously unrecognized in this condition. Late diagnosis of this relatively new syndrome in all our patients confirms the difficulty of the nosologic definition of mentally retarded individuals on clinical grounds alone. On the other hand, the Lujan-Fryns syndrome appears to be more common than one would have thought.
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PMID:X-linked mental retardation with marfanoid habitus: first report of four Italian patients. 201 63

Two behavior genetic research strategies have been utilized to understand gene influences in autism. There is overwhelming evidence for gene involvement, although an exact mode of inheritance has not yet been elucidated. Family and twin studies illustrate that the clinical phenotype of autism is not sufficient to characterize the underlying genotype(s) involved. Exactly what should be included in the phenotype remains elusive. Cognitive and social deficits are indicated as milder variants of the autism phenotype, but precisely how to define these deficits requires further research. Furthermore, more complex models of inheritance (e.g., two-locus models--multifactorial and major gene) may be necessary to explain gene influences in autism. Genetic heterogeneity is indicated in autism, with an X-linked disorder, fragile X, and an autosomal dominant disorder, tuberous sclerosis, together accounting for perhaps 8% to 11% or more of cases of autism. Differences in family patterns (i.e., recurrence risks) of neuropsychiatric disorders between autism with and without mental retardation or other clinically defined groups (e.g., males and females) are suggested. Whether these differences represent genetic heterogeneity or multifactorial inheritance with varying thresholds (e.g., of severity or sex differences) cannot be distinguished on the basis of the data available to date. Autosomal recessive inheritance is suggested in a subgroup of families with autism, but the proportion of all autism that may be accounted for by autosomal recessive inheritance is unknown. Evidence exists that stoppage occurs in families with autism, however, and this can affect accurate estimates of segregation ratios when not taken into account. Future family studies need to report (1) exact ascertainment schemes and specification of probands and (2) sex and birth order of affected siblings, including sibship size, so that data may be pooled and such effects can be tested. Investigations of populations with fragile X or tuberous sclerosis as well as those with autism (without known genetic disorders) will identify the etiologic basis of these associations. Such associations may be due to linkage of genes underlying autism and those underlying the known genetic disorders (i.e., linkage disequilibrium) or shared brain pathophysiology or merely shared overt behaviors. Until such mechanisms are elucidated, we can use only empiric risk figures in genetic counseling situations of autism, assuming that no known genetic or environmental cause is identified. Pooling available data from family and twin studies, the following empiric risks are suggested for genetic counseling purposes. An average sibling risk (frequency of affected siblings among all siblings) based on pooled data is 3% (i.e., 57/1698).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Genetic influences in autism. 204 27


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