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

Down's syndrome (DS) is a genetic disorder involving an excess of chromosome 21 (trisomy 21) in approximately 96% of the cases and comprises approximately 15% of the population with mental retardation (Heller, 1969). In addition to the constitutional mental deficiencies associated with the syndrome many DS patients develop dementia associated with Alzheimer's disease (AD) in their later years of life (Thase et al., 1984). The genetic locus for Cu,Zn-superoxide dismutase (SOD1), a key enzyme in free radical metabolism, is located on chromosome 21, and the activity level of this enzyme is elevated by approximately 50% in a variety of cells of DS patients (see Kedziora and Bartosz, 1988; Sinet, 1982). Because alterations in free radical metabolism may be involved in neuronal death and may be associated with a number of pathological manifestations of DS, it is important to understand the role of free radical metabolism in cognitive impairments of DS, the topic discussed in this chapter.
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PMID:The role of alterations in free radical metabolism in mediating cognitive impairments in Down's syndrome. 145 May 86

Recent evidence suggests that Alzheimer's disease is an etiologically heterogeneous disorder. A human model of Alzheimer's disease exists that avoids such problems of etiologic heterogeneity. Down syndrome (DS), trisomy 21, is a genetic disorder in which an extra portion of chromosome 21 leads to mental retardation, short stature, and phenotypic abnormalities. Prior investigations by others have shown that DS subjects over 40 years of age demonstrate neuropathologic and neurochemical defects postmortem that are virtually indistinguishable from those found in brains of Alzheimer's disease patients and a universal cognitive deterioration more severe in demented than nondemented older DS subjects. In our study, these nondemented older DS subjects show a distinctive pattern of age-related deficits, while a more global pattern is seen in demented older DS subjects. Dementia occurs in 40% of older DS subjects. We find that in older demented DS subjects positron emission tomography (PET) shows identical patterns of abnormal glucose metabolism as those described previously in Alzheimer's disease patients, selectively involving the phylogenetically newer association areas of parietal and temporal neocortices but sparing primary sensory and motor regions. Further, we find in older demented DS patients quantitative computer-assisted tomography (CT) indicates accelerated neuronal loss and brain atrophy, similar to that previously shown in Alzheimer's disease patients. As a potential use of the DS model, we observed a case of DS with dementia but without mental retardation. This case suggests that expression of dementia in DS may involve genes on chromosome 21 other than in the "obligatory" distal segment of the q arm. Alternatively, differential expression of genes on the q arm of chromosome 21 might cause dementia without phenotypic features and mental retardation.
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PMID:Nature of mental retardation and dementia in Down syndrome: study with PET, CT, and neuropsychology. 149 38

We describe 3 children (from two families) with a multisystemic disorder characterized by mental retardation, nonprogressive ataxia, polyneuropathy, hepatopathy during infancy and growth retardation. Due to the clinical similarities to a recently recognized disorder associated with carbohydrate-deficient transferrin, we examined serum transferrin by means of isoelectric focusing, and found increases in disialo transferrin and asialotransferrin. Removal of sialic acid with neuraminidase revealed the same transferrin phenotypes as in their parents. Similarly, carbohydrate-deficient fractions of serum alpha 1-antitrypsin were also detected. Therefore, the diagnosis was made of the recently identified carbohydrate-deficient glycoprotein syndrome. This is a genetic disorder with distinctive clinical features and multiple carbohydrate-deficient glycoproteins. These seem to be the first reported Japanese patients with this syndrome.
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PMID:The carbohydrate deficient glycoprotein syndrome in three Japanese children. 159 May 25

The concept of anticipation, the occurrence of a genetic disorder at progressively earlier ages in successive generations, has been debated from the early years of this century, with myotonic dystrophy as the most striking example. Throughout most of this period there has been controversy as to whether the phenomenon resulted from observational and ascertainment biases or reflected a more fundamental mechanism. The recent discovery of inherited unstable DNA sequences, first in fragile-X mental retardation and now in myotonic dystrophy, not only confirms that anticipation indeed has a true biological basis but provides a specific molecular mechanism for it; this discovery can explain many of the puzzling anomalies in the inheritance of myotonic dystrophy and may prove relevant to comparable problems in other genetic disorders.
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PMID:Anticipation in myotonic dystrophy: new light on an old problem. 160 89

Fragile X [fraX] syndrome is a common hereditary disorder associated with a fragile site marker at Xq27.3 which clinically presents as a form of mental retardation (MR). Postmortem investigation of 3 fraX positive males with mild to moderate MR did not document any gross neuropathological changes. Golgi analysis of neocortical dendritic spine morphology extended our previous observations of immature, long, tortuous spines in one adult case of fraX (Rudelli, et al., Acta Neuropathologica 67:289-295, 1985) to 2 new cases. Evidence for similar dendritic spine abnormalities was found, although Golgi analysis was less than optimal because of incomplete dendritic stain impregnation. Neocortical intra-layer cell density was also investigated in all 3 cases. Cresyl violet stained neurons were counted in 10 randomly selected fields in neocortical layers II-VI of cingulate and temporal association areas (Brodmann's areas 23 and 38). Neuron counts in fraX and control neocortex showed no significant differences. Thus, abnormal dendritic spine morphology with preservation of neuronal density appears to characterize the neocortex in individuals with this common form of mental retardation.
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PMID:Analysis of neocortex in three males with the fragile X syndrome. 172 12

Clinical and ultrastructural study of four cases of Coffin-Lowry syndrome (CLS), a heritable disorder with peculiar facies, stooped posture, vertebral changes, and mental retardation, is reported. Three of the four cases had myelopathy caused by calcification of the ligamenta flava in early adulthood. These patients demonstrated that CLS is a calcium pyrophosphate dihydrate crystal deposition disease, and it is postulated that a metabolic abnormality in collagen and in proteoglycans are responsible for some aspects of CLS.
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PMID:Coffin-Lowry syndrome associated with calcium pyrophosphate crystal deposition in the ligamenta flava. 173 5

An infant with short stature and progressive skin lesions of cheeks and dorsum of the hands is described. Further problems such as recurrent diarrhoea and respiratory infections suggested zinc-deficiency, malabsorption-syndrome, Bloom syndrome and early Lupus Erythematosus respectively. Finally Rothmund-Thomson syndrome was diagnosed. This rare genetic disorder is characterized by variable expression of typical cutaneous changes, cataracts, skeletal anomalies, short stature, abnormal hair growth and defective nails and teeth, mental retardation, hypogonadism and a typical facial appearance.
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PMID:[An infant with short stature and red cheeks (Rothmund-Thomson syndrome)]. 177 48

Dubowitz syndrome is a rare hereditary disorder whose main features are intra-uterine and post-natal growth retardation, characteristic facies, microcephaly, mental retardation and poor feeding. Because of the eczema which was present in half of the cases after 4 years of age, it cannot be mistaken for the more frequent fetal alcohol syndrome. We report 5 cases, among whom two sibs, confirming the recessive autosomal mode of inheritance and the necessity for genetic counseling.
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PMID:[Dubowitz syndrome. A diagnosis not to be missed]. 179 48

Fragile X syndrome, an X-linked genetic disorder, is the third most common cause of mental retardation. The following is a case of a 6-year-old boy with fragile X syndrome and its characteristic cognitive and behavioral symptomatology, including attention deficit hyperactivity disorder. In addition, this child experienced initial insomnia and nocturnal enuresis, problems not previously reported with fragile X. Previous pharmacological treatment of the syndrome's behavioral difficulties and attention deficit has included stimulants, folic acid, and neuroleptics. This is the first report of the successful use of imipramine. Imipramine also improved the boy's insomnia and enuresis, whereas methylphenidate caused an overall worsening of his condition.
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PMID:Imipramine treatment of ADHD in a fragile X child. 193 2

The carbohydrate-deficient glycoprotein syndrome is a newly described hereditary disorder which may be due to a defect in the glycoprotein metabolism. Predominant symptoms are mental retardation, epilepsy, cerebellar ataxia, polyneuropathy, squint, retinitis pigmentosa, retarded growth, hypothyroidism and liver steatosis. Increased serum glycoprotein-deficient transferrin is a marker of the disease and confirms the diagnosis. We describe four Norwegian children with this syndrome. Olivopontocerebellar degeneration was found upon examination of the brain in two patients who died.
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PMID:[The carbohydrate deficient glycoprotein syndrome]. 1044 Oct 90


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