Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is proposed that chronic moderate hyperhomocysteinemia has a causal role in a number of common diseases of late life, including occlusive vascular disease, cognitive decline, senile osteoporosis and presbyopia. These diseases are seen as clinical counterparts of the main manifestations of homocystinuria (vascular occlusions of arteries and veins, mental retardation, osteoporosis and ectopia lentis, respectively) that develop only after many years of exposure to moderately elevated homocysteine (Hcy) levels. The multisystem toxicity of Hcy is attributed to its spontaneous chemical reaction with many biologically important molecules, primarily proteins. The formation of these Hcy-adducts is dependent on time and Hcy concentration and leads to loss or diminution of function of the derivatized molecules. Irreversible homocysteinylation of long-lived proteins should lead to cumulative damage and progressive clinical manifestations. Fibrillin 1 is seen as the paradigm of extracellular connective tissue proteins that are specially susceptible to Hcy (and presumably Hcy thiolactone) attack. The prominent presence of epidermal growth factor (EGF)-like domains in fibrillin and in many other extracellular proteins of the coagulation, anticoagulation, and lipoprotein transport pathways, all of which malfunction in hyperhomocysteinemia, suggests that EGF-like domains may be preferential sites of homocysteinylation.
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PMID:Mechanisms of homocysteine toxicity on connective tissues: implications for the morbidity of aging. 1072 8

Wolcott-Rallison syndrome (WRS) is a rare, autosomal recessive disorder characterized by permanent neonatal or early infancy insulin-dependent diabetes. Epiphyseal dysplasia, osteoporosis and growth retardation occur at a later age. Other frequent multisystemic manifestations include hepatic and renal dysfunction, mental retardation and cardiovascular abnormalities. On the basis of two consanguineous families, we mapped WRS to a region of less than 3 cM on chromosome 2p12, with maximal evidence of linkage and homozygosity at 4 microsatellite markers within an interval of approximately 1 cM. The gene encoding the eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3) resides in this interval; thus we explored it as a candidate. We identified distinct mutations of EIF2AK3 that segregated with the disorder in each of the families. The first mutation produces a truncated protein in which the entire catalytic domain is missing. The other changes an amino acid, located in the catalytic domain of the protein, that is highly conserved among kinases from the same subfamily. Our results provide evidence for the role of EIF2AK3 in WRS. The identification of this gene may provide insight into the understanding of the more common forms of diabetes and other pathologic manifestations of WRS.
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PMID:EIF2AK3, encoding translation initiation factor 2-alpha kinase 3, is mutated in patients with Wolcott-Rallison syndrome. 1093 83

Osteoporosis screening of adults ages 40 to 60 who attended community-based adult training centers was conducted utilizing dual-energy X-ray absorptiometry (DEXA) measurements of the calcaneus. Valid measurements were obtained on 107 individuals, a response rate of 94%. One fifth of the sample (21%) had osteoporosis and 34% had osteopenia. On multiple regression analysis, the most significant predictors of BMD were Down syndrome, mobility status, and race. Future studies involving larger samples of middle-age adults with mental retardation/developmental disabilities will clarify the need and optimum age for osteoporosis screening.
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PMID:Screening for osteoporosis in community-dwelling adults with mental retardation. 1098 Nov 93

We report on a Japanese family having an autosomal dominant neurodegenerative disease with chromosomal instability and radiosensitivity. Clinical manifestations of affected members included short stature, osteoporosis, severe dental caries, and various neurological abnormalities, such as mental retardation, depression, dysarthria, hyperreflexia, and ataxic gait. MRI demonstrated a markedly atrophic spinal cord and degeneration of the white matter. Cytogenetic examination showed spontaneous chromosome rearrangements at 14q11.2 and hypersensitivity to radiation and bleomycin. The degree of these cytogenetic abnormalities was significantly higher in the patients than in normal controls but lower than in patients with ataxia telangiectasia or Nijmegen breakage syndrome. Moreover, genetic anticipation was observed in this family: the age of disease onset became earlier, MRI abnormalities more extensive, and the chromosome hypersensitivity to radiation increased in successive generations. We speculate that a basic defect in this family is a mutation in the gene that is responsible for DNA double-strand breakage repair.
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PMID:Japanese family with an autosomal dominant chromosome instability syndrome: a new neurodegenerative disease? 1103 37

The pathological sequelae of untreated homocystinuria due to cystathionine beta-synthase deficiency include ectopia lentis, osteoporosis, thromboembolic events and mental retardation. They occur at a significantly higher rate with poorer mental capabilities (mean IQ = 57) in the untreated pyridoxine-nonresponsive individuals. The mental capabilities of 23 pyridoxine-nonresponsive individuals with 339 patient-years of treatment were assessed using age-appropriate psychometric tests and were compared to those of 10 unaffected siblings (controls). Of the 23 individuals, 19 were diagnosed through newborn screening with early treatment, two were late-detected and two were untreated at the time of assessment. Thirteen of the newborn, screened group who were compliant with treatment had no complications, while the remaining 6, who had poor compliance, developed complications. Good compliance was defined by a lifetime plasma free homocystine median < 11 micromol/L. The newborn screened, good compliance group (n = 13) with a mean age of 14.4 years (range 4.4-24.9) had mean full-scale IQ (FIQ) of 105.8 (range 84-120), while the poorly compliant group (n = 6) with a mean age of 19.9 years (range 13.8-25.5) had a mean FIQ of 80.8 (range 40-103). The control group (n = 10) with mean age of 19.4 years (range 9.7-32.9) years had a mean FIQ of 102 (range 76-116). The two late-detected patients aged 18.9 and 18.8 years had FIQ of 80 and 102, while the two untreated patients aged 22.4 and 11.7 years had FIQ of 52 and 53, respectively. There was no statistical evidence of significant differences between the compliant, early-treated individuals and their unaffected siblings (controls) except for the FIQ, which was significantly higher than that of the unaffected siblings (p = 0.0397). These data, despite the relatively small numbers, suggest that early treatment with good biochemical control (lifetime plasma free homocystine median < 11 micromol/L) seems to prevent mental retardation.
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PMID:The intellectual abilities of early-treated individuals with pyridoxine-nonresponsive homocystinuria due to cystathionine beta-synthase deficiency. 1159 48

Cystathionine beta-synthase (CBS) deficiency is the most common cause of homocystinuria. It is inherited as an autosomal recessive trait and common clinical features are: dislocation of the optic lens, osteoporosis, mental retardation, and thromboembolism. We determined the molecular basis of CBS deficiency in 36 Australian patients from 28 unrelated families, using direct sequencing of the entire coding region of the CBS gene. The G307S and I278T mutations were the most common mutations. They were present in 19% and 18% of independent alleles, respectively. In total, seven novel and 20 known mutations were detected. Of those, the two novel missense mutations (C109R and G347S), as well as two known missense mutations (L101P and N228K), were expressed in E. Coli. All mutant proteins completely lacked catalytic activity. Furthermore, we studied the correlation between genotype and the biochemical response to pyridoxine treatment in the patients of whom 13 were pyridoxine responsive, 21 were non-responsive, and two were partially responsive. The G307S mutation always resulted in a severe non-responsive phenotype, whereas I278T resulted in a milder B6 responsive phenotype. From our results, we were also able to establish three other mild mutations: P49L, R369C, and V371M.
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PMID:The molecular basis of cystathionine beta-synthase deficiency in Australian patients: genotype-phenotype correlations and response to treatment. 1212 92

Albright hereditary osteodystrophy is a hereditary metabolic disorder of dominant autosomal etiology that is commonly characterized by short stature, round face, small metacarpus and metatarsus, mental retardation, osteoporosis, subcutaneous calcification, variable hypocalcemia, and hyperphosphatemia. In this study, we report a clinical case of a 17-year-old woman with Albright hereditary osteodystrophy, and we discuss her clinical, radiographic, and laboratory test characteristics together with the oral manifestations, and we correlate them with the characteristics found in the literature. We also discuss the odontological management of treatment of related periodontal disease and planning for corrections of related malocclusions.
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PMID:Oral manifestations of Albright hereditary osteodystrophy: a case report. 1224 36

We describe two sibs with postnatal-onset growth deficiency, microcephaly, cataract, prominent supraorbital ridge, large joint contractures, severe osteoporosis, cortical dysplasia, cerebellar atrophy, and mental retardation. The combination appears to constitute a previously undescribed syndrome inherited in an autosomal recessive pattern.
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PMID:Postnatal growth failure, microcephaly, mental retardation, cataracts, large joint contractures, osteoporosis, cortical dysplasia, and cerebellar atrophy. 1249 36

Homocystinuria due to cystathionine beta-synthase deficiency is the second most treatable aminoacidopathy. The reported incidence varies from 1 in 344,000 worldwide to 1 in 65,000 in Ireland. Untreated patients with homocystinuria have severe hyperhomocysteinaemia. Amongst its pathological sequelae, which include mental retardation, ectopia lentis and osteoporosis, vascular events remain the major cause of morbidity and mortality in untreated patients. Recognized modalities of treatment include pyridoxine, in combination with folic acid and vitamin B12; methionine-restricted, cystine-supplemented diet; and betaine. The natural history of vascular events is such that half will have an event before age 30 years and there is a predicted one event per 25 years at the time of maximal risk. In 158 patients with 2822 patient-years of treatment, there would be a predicted 112 events if left untreated, but instead only 17 vascular events were recorded during treatment (relative risk 0.09, 95% CI 0.036 to 0.228; p < 0.0001). Appropriate chronic treatment to lower hyperhomocysteinaemia is effective in reducing the potentially life-threatening vascular risk in patients with homocystinuria. These findings may also have relevance to the significance of mild hyperhomocysteinaemia that is commonly found in patients with premature vascular disease.
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PMID:Classical homocystinuria: vascular risk and its prevention. 1288 65

Polyamines (putrescine, spermidine, spermine) are ubiquitous, simple molecules that interact with a variety of other molecules in the cell, including nucleic acids, phospholipids and proteins. Various studies indicate that polyamines are essential for normal cell growth and differentiation. Furthermore, these molecules, especially spermine, have been shown to modulate ion channel activities of certain cells. Nonetheless, little is known about the specific cellular functions of these compounds, and extensive laboratory investigations have failed to identify a heritable condition in humans in which polyamine synthesis is perturbed. We report the first polyamine deficiency syndrome caused by a defect in spermine synthase (SMS). The defect results from a splice mutation, and is associated with the Snyder-Robinson syndrome (SRS, OMIM_309583), an X-linked mental retardation disorder. The affected males have mild-to-moderate mental retardation (MR), hypotonia, cerebellar circuitry dysfunction, facial asymmetry, thin habitus, osteoporosis, kyphoscoliosis, decreased activity of SMS, correspondingly low levels of intracellular spermine in lymphocytes and fibroblasts, and elevated spermidine/spermine ratios. The clinical features observed in SRS are consistent with cerebellar dysfunction and a defective functioning of red nucleus neurons, which, at least in rats, contain high levels of spermine. Additionally, the presence of MR reflects a role for spermine in cognitive function, possibly by spermine's ability to function as an 'intrinsic gateway' molecule for inward rectifier K(+) channels.
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PMID:X-linked spermine synthase gene (SMS) defect: the first polyamine deficiency syndrome. 1450 4


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