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

Expansion of trinucleotide repeats is now recognized as a major cause of neurological disease. At least seven disorders result from trinucleotide repeat expansion: X-linked spinal and bulbar muscular atrophy (SBMA), two fragile X syndromes of mental retardation (FRAXA and FRAXE), myotonic dystrophy, Huntington's disease, spinocerebellar ataxia type 1 (SCA1), and dentatorubral-pallidoluysian atrophy (DRPLA). The expanded trinucleotide repeats are unstable, and the phenomenon of anticipation, i.e., worsening of disease phenotype over successive generations, correlates with increasing expansion size. In this review, we compare the clinical and molecular features of the trinucleotide repeat diseases, which may be classified into two types. Fragile X and myotonic dystrophy are multisystem disorders usually associated with large expansions of untranslated repeats, while the four neurodegenerative disorders, SBMA, Huntington's disease, SCA1, and DRPLA, are caused by smaller expansions of CAG repeats within the protein coding portion of the gene. CAG repeats encode polyglutamine tracts. Polyglutamine tract expansion thus appears to be a common mechanism of inherited neurodegenerative disease. Although polyglutamine tract lengthening presumably has a toxic gain of function effect in the CAG trinucleotide repeat disorders, the basis of this neuronal toxicity remains unknown.
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PMID:Trinucleotide repeat expansion in neurological disease. 799 66

Two half-brothers and their mother had symptomatic pyruvate dehydrogenase complex deficiency. The infants had severe congenital lactic acidosis, seizures, and apneic spells and died at the ages 3 and 4 months. The mother was less symptomatic with mental retardation, truncal ataxia, and dysarthria. The residual pyruvate dehydrogenase activities in cultured skin fibroblasts from the 2 infants and their mother were 7, 15, and 10% of control values. Immunoblot analysis showed negligible amounts of E1 alpha and E1 beta subunits of the complex. Northern blot analysis for the E1 alpha subunit showed normal results. In the 2 sons, complementary DNA sequence analysis revealed a cytosine to thymine mutation in exon 4, resulting in a change of arginine 127 to tryptophan in the E1 alpha subunit. Restriction enzyme analysis of the polymerase chain reaction product representing exon 4 of the E1 alpha gene revealed that the mother was a heterozygotes. Complementary DNA restriction analysis and methylation analysis of the X chromosome DXS255 loci revealed skewed activation of the mutant allele, consistent with the deficient pyruvate dehydrogenase activity in the mother's fibroblasts. The milder maternal phenotype is consistent with variable X-inactivation patterns in different organs of female heterozygotes.
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PMID:Pyruvate dehydrogenase deficiency: molecular basis for intrafamilial heterogeneity. 802 67

Cowden syndrome is an autosomal dominant condition of multiple hamartomas. Patients with this phakomatosis have an increased risk of breast cancer and thyroid tumours. Lhermitte-Duclos disease is usually a sporadic condition of cerebellar ganglion cell hypertrophy, ataxia, mental retardation, and self-limited seizure disorder. We describe a three generation family with Cowden syndrome and Lhermitte-Duclos disease. Karyotyping performed on the peripheral lymphocytes of the proband and her affected mother showed a 46,XX complement. Single strand conformational polymorphism analysis failed to show any germline p53 mutations as a cause of the syndrome in this family.
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PMID:Cowden syndrome and Lhermitte-Duclos disease in a family: a single genetic syndrome with pleiotropy? 807 72

The triplet repeat sequences (CGG)n, (GCT)n, and (CAG)n, which naturally occur in the human genome, can be autonomously expanded in human DNA by an as yet unknown mechanism. These in part excessive expansions have been causally related to human genetic diseases, the fragile X (Martin-Bell) syndrome, to myotonic dystrophy (Curschmann-Steinert), to spinal and bulbar muscular atrophy (Kennedy disease), and recently to Huntington disease. A GCC trinucleotide repeat was found to be expanded and methylated in the fragile site FRAXE on the human X chromosome. These findings were associated with mental retardation (Knight et al., 1993). In spinocerebellar ataxia type 1 (SCA1), a polymorphic CAG repeat was found to be unstable and expanded in individuals with that disease (Orr et al., 1993). We have demonstrated in in vitro experiments that the synthetic oligodeoxyribonucleotides (CGG)17, (CGG)12, (GCC)17, (CG)25, (CTG)17, or (CAG)17 plus (GTC)17, in the absence of added natural DNA, can be expanded with Taq polymerase in the polymerase chain reaction (PCR). Some expansion can already be detected after 4 PCR cycles. The E. coli Klenow DNA polymerase also functions in a similar amplification and expansion reaction performed at 37 degrees C without cycling. Other oligodeoxyribonucleotides, like, (CGG)7, (CGGT)13, or (TAA)17, are devoid of this property or have very low activity. The cytidine-methylated polymers (GCC)17 or (CG)25 yield expansion products of considerably reduced chain lengths. The expansion of the polymer (CGG)17 is affected by cytidine methylation to a lesser degree. A specific sequence and/or secondary structure and high CG content appear to be requirements for this expansion reaction by a possible slippage mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enzymatic amplification of synthetic oligodeoxyribonucleotides: implications for triplet repeat expansions in the human genome. 811 62

The recent observation that the mutation underlying a number of genetic diseases including fragile sites, FRAXA and FRAXE (associated with mental retardation), myotonic dystrophy, spinal and bulbar muscular atrophy (Kennedy's disease), Huntington's disease and spinocerebellar ataxia type 1 are caused by the expansion of a trinucleotide repeat sequence will lead to interest in the identification of such sequences in regions related to other diseases. We report here the identification of all ten classes of trinucleotide repeats within a 2 Mbp region of 4p16.3 containing the Huntington's disease (HD) gene. Fifty one triplet repeats were identified and localised on a high resolution restriction map of a cosmid contig covering this region. This included the triplet repeat (CAG)n, which has subsequently been shown to be expanded in Huntington's disease patients.
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PMID:Distribution of trinucleotide repeat sequences across a 2 Mbp region containing the Huntington's disease gene. 816 55

A new group of recessively inherited metabolic disorders affecting glycoprotein metabolism has been identified--the carbohydrate-deficient-glycoprotein (CDG) syndromes. Here the course and clinical expression of CDG syndrome type I in 13 patients who have passed the age of 15 years are described. All presented with early onset psychomotor retardation, in most cases combined with slight facial dysmorphic features, some degree of hepatic dysfunction, and in one case, pericardial effusion. About half of the patients had subcutaneous lipodystrophy and comatose or stroke-like episodes during childhood. After the age of 15 the disease was mainly characterised by neurological symptoms consisting of non-progressive ataxia associated with cerebellar hypoplasia, stable mental retardation, variable peripheral neuropathy, and strabismus. One third of the patients had generalised seizures, usually sporadic, and all had retinal pigmentary degeneration. In all cases there was more or less pronounced thoracic deformity and no female had passed puberty. Also, the oldest female showed premature aging. Severe internal organ symptoms, which are common in pediatric patients, were absent. All patients had highly raised serum concentrations of the biochemical marker carbohydrate-deficient transferrin, which can be used to verify the diagnosis. It is concluded that after childhood, CDG syndrome type I is a largely non-progressive disease compatible with a socially functioning but dependent lifestyle.
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PMID:Carbohydrate-deficient glycoprotein syndrome: clinical expression in adults with a new metabolic disease. 820 22

Fourteen patients (10 boys, 4 girls) aged from 4 months to 14 years old were diagnosed with mitochondrial disease based on the clinical manifestations together with abnormal muscle mitochondrial morphologies. Their clinical diagnoses included Leigh syndrome, three; Menkes' syndrome, three; Kearns-Sayre syndrome, two; myoclonic epilepsy with ragged fibres, one; and infant-onset progressive myoclonic epilepsy, one; fatal infantile mitochondrial myopathy, one; fatty acid oxidation defect, two; and myopathy with cardiopathy, one. Organs involved other than muscles included central nervous system, ten; heart, six; eye, two; liver, two; and kidney, two. Clinical manifestations varied to include hypotonia, seizures, myoclonus, mental retardation, nystagmus, ataxia, ptosis, ophthalmoplegia, retinal degeneration, muscle atrophy, spasticity etc. Nine had an abnormal rise in lactate after glucose loading. Ragged-red fibres were found in four patients. Abnormal mitochondrial morphology included abnormal accumulation, abnormal cristae pattern of tubular, concentric, or parallel form, some contained osmiophilic inclusion bodies. One patient of Leigh syndrome had had brain necropsy which showed intramyelin splitting of myelinated axons.
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PMID:Clinical manifestation of mitochondrial diseases in children. 821 54

A 35-year-old female was reported who presented early onset and slowly progressive ataxia and retrocollis which appeared at the age of nine. On admission, neurological examination revealed cerebellar ataxia, dystonia of the neck and the right arm, myoclonus of the neck and the shoulder, slight mental retardation, supranuclear upper gaze palsy, and sensorineural hearing loss. Laboratory examination showed high serum CK activity. Electromyography and muscle biopsy findings suggested slight muscular involvement. CSF level of HVA and 5-HIAA were reduced. MRI demonstrated marked cerebellar atrophy and slight atrophy of the brain stem. To our knowledge, the characteristic combination of the neurological sign in this case has not been reported. This case was compared with EOCA (early onset cerebellar ataxia with retained tendon reflexes) and other juvenile onset cerebellar ataxia and dystonia.
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PMID:[A case of juvenile onset ataxia with dystonia, myoclonus, sensorineural hearing loss and mental retardation]. 826 7

We report myoclonic epilepsy with ragged-red fibers (MERRF) syndrome in a Chinese family with confirmed mitochondrial DNA point mutation. Six members of the family including the grandmother, two siblings, and three grandchildren were affected. Among them, action myoclonus was seen in five; short stature, muscle weakness, and mental retardation in four; lactic acidosis, hearing impairment, and ataxia in two; and seizures in one. Muscle biopsy from two affected siblings revealed ragged-red fibers and abundant subsarcolemmal mitochondria with paracrystalline inclusions. Pedigree analysis suggests a maternal transmission. Analysis of mitochondrial DNA showed a point mutation from A to G at the 8344th nucleotide position located in the tRNA(Lys) gene. To our knowledge, this is the first report of MERRF syndrome with such genetic defect from a Chinese family. The present and previous reports support the notion that mitochondrial DNA point mutation at the 8344th nucleotide position is the most common cause of MERRF syndrome.
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PMID:Myoclonic epilepsy with ragged-red fibers (MERRF) syndrome: report of a Chinese family with mitochondrial DNA point mutation in tRNA(Lys) gene. 793 36

The term of dentatorubral and Pallidoluysian atrophy (DRPLA) was first introduced by Smith, who proposed that there was a combination of cerebellar ataxia with choreoathetosis based on DRPL lesions. In 1972, Naito et al. reported two families with progressive myoclonus epilepsy (PME) syndrome with cerebellar ataxia, and hyperactive deep tendon reflexes. In 1977, Oyanagi et al. reported 4 autopsied cases of PME, and pointed out degenerative lesions in the DRPL systems. In 1982, Naito and Oyanagi reported this type of PME to be hereditary DRPLA, with a clinicopathological disease entity. This type of PME with DRPLA has been made a major category, especially in Japan. In this article, clinicopathological features of the hereditary DRPLA will be reviewed on the basis of 45 patients with this disease. The disease was inherited as an autosomal dominant fashion, and induces a wide rage of clinical features depending upon the age of onset, ranging from 3 years to 69 years of age. The initial symptoms were variable according to the age of onset and mental retardation was the most prominent symptom in the patients in which the disease started in the first decade and with an epileptic seizure in the second decade. In the following next two decades, the incidence of epileptic seizure, as initial symptoms was decreased to 23% and gait disturbance and ataxia in 38% of the patients, which increased to 73% in the 5th and 6th decades. The cardinal symptoms of hereditary DRPLA includes mental retardation, epileptic seizure and myoclonus, cerebellar ataxia with gait disturbances, psychological symptoms including clonus, cerebellar ataxia with gait disturbances, psychological symptoms including character changes, and dementia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Hereditary dentatorubro-pallidoluysian atrophy (DRPLA): clinical studies on 45 cases]. 827 85


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