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

In man, the period of maximum risk for the embryo and foetus is between the second and tenth week after conception. The most frequent and most severe malformation is microcephaly which in extreme cases is accompanied by mental retardation. The results of studies in experimental animals and man agree that it is impossible to demonstrate any increased risk of malformation with doses below 15 rads, and that the increase over the spontaneous incidence of malformation is slight at doses below 25 rads. A very small increase in the frequency of leukaemias and cancers has been observed after irradiation in utero for pelvimetry, which delivers a few rads; it can be estimated from these data that a dose of 2 rads induces at the most the risk of one case of cancer in 2,000 children. In practice, it is only exceptionally that an abortion is advised after a diagnostic radiological examination, since the doses in these circumstances are relatively low. A therapeutic termination of pregnancy should be advised when the dose is greater than 20 rads, but it is necessary to take into account other medico-social factors. Conversely, it is important to avoid any irradiation in women who could be pregnant and in particular avoid any irradiation of the true pelvis during the 10 days prior to menses and especially if there has been a delay in the start of menstruation. In pregnant women radiological examinations should only be made if they are of paramount importance for the mother, and all precautions taken to reduce the dose to the uterus in the absolute minimum.
Bull Cancer 1979
PMID:[The problems raised by the irradiation of pregnant women. Effects of ionizing radiations on the embryon and foetus (author's transl)]. 11 30

This paper is an introduction to the cytogenetic biology of man. It deals with the role of chromosome abnormalities in prenatal death, malformation syndromes, mental retardation, malformation/mental retardation syndromes, abnormalities of sex determination, sex differentiation and sexual function, cancer, and certain genetic disorders in which chromosome abnormalities are seen commonly. Down syndrome is discussed as an important and common example of a malformation/mental retardation syndrome.
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PMID:Clinical cytogenetics: part 1. 14 67

Children with chronic metabolic acidosis should be investigated to determine the presence of an organic acid, especially when the plasma electrolyte profile shows a deficiency of anion. One of the organic acids that should be looked for in such a patient is lactic acid. Lactic acidosis due to tissue hypoxia is a well-known phenomenon (e.g., in shock and cardiopulmonary disease) and has not been discussed in this essay; nor has lactic acidosis due to exogenous causes like infusion of fructose or sorbitol, or admiministration of phenformin. Chronic lactic acidosis in infancy is a rare condition. It may be associated with glycogen storage disease Type 1, fructose diphosphatase deficiency, methylmalonic acidemia, propionic acidemia, pyruvate carboxylase or dehydrogenase deficiency and Leigh's subacute necrotizing encephalomyelopathy (SNE). Some patients with chronic lactic acidosis do not have nay of these diseases and comprise an "idiopathic" group. This is a heterogeneous group, probably having several different causes for the metabolic error. In Leigh's SNE, a metabolic block in the formation of thiamine triphosphate in brain has been demonstrated and has been attributed to the presence of an inhibitor of thiamine pyrophosphate-adenosine triphosphate (TPP-ATP) phosphoryl transferase in body fluids. The inhibitor has also been encountered in cases of intermittent cerebellar ataxia and of primary hypoventilation (Ondine's curse), which may represent variants of Leigh's disease. Increased blood levels of lactate, pyruvate and alanine frequently are encountered in SNE, but it still is not clear whether they are due to a primary or secondary disturbance in the catabolism of pyruvate. Disturbed lactate and pyruvate metabolism has also been encountered in isolated cases of mental retardation and growth failure, in mitochondrial myopathies and in polyneuropathies, and may be expected to occur in Wernicke's encephalopathy. Finally, it has been noted in malignancy and in association with other rare metabolic disorders.
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PMID:Lactic acidosis in childhood. 17 59

Parents of 751 children affected by cancer/leukemia, congenital heart disease, strawberry nevus or mental retardation have been investigated with respect to their reproductive history and their exposure to risk factors for spontaneous abortion. Differences between the four groups were established for the number of children in the sibship, the proportion of multigravidae and the spontaneous abortion rate among these women. The greatest differences were observed in the two groups of malformed children compared with the other two groups, being as marked in those with a severe malformation (heart defect) as in those with a benign one (strawberry nevus). Taking known risk factors for spontaneous abortion into account did not explain the observed differences. An etiological hypothesis is put forward which takes account of the high proportion of quantitative abnormalities of the karyotype associated with congenital heart disease and spontaneous abortion.
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PMID:Spontaneous abortions in sibship of children with congenital malformation or malignant disease. 26 88

Pathological type complications associated with 46 cases of neurofibromatosis in children under 12 are reported. It is noted that in 65.2% of the cases there are mental retardation, usually serious. More than 50% (24 cases) had some type of tumoration. All were benign with the exception of a suprarenal neuroblastoma that caused arterial hypertension and histological characteristics of malignancy. Fifteen tumors were located in the optica ways, one in the mediastinum, one in the abdomen, one in the paravertebral area, one which was a craneal plexiform tumor and four of the moluscum pendulum type on the eyelids or in neighbouring regions. Twelve children suffered from some type of seizures (Salaam's spasms, tonic-clonic, myoclonic, atonic and versive). Radiological abnormalities were very frequent in the simple X rays as well as in those in which contrast medium was used. In four cases malformations of the midline were observed, three of which were non-communicating cysts of the septum pellucidum, the other agenesis of the corpus callosum. Neurofibromatosis was further seen associated iwth Bourneville's syndrome, Morquio's syndrome, Batten's type of lipofuscinosis, facial or generalized hemihypertrophia and stenosis of the aqueduct. Heredity was dominant autosomic in 16 cases, the rest being due to possible recent mutations.
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PMID:[Pathological complications in 46 cases of neurofibromatosis in children (author's transl)]. 82 74

A two year old female child with bilateral wilms tumor (WT) along with multiple congenital anomalies like bilateral aniridia with congenital cataracts and nystagmus, microcephaly, mental retardation and ventricular septal defect has been described. The karyotype analysis revealed 46 xx, del 11p 13-14.1. Association of ventricular septal defect with the classical features of 'Aniridia-Wilms' tumor association' is an unusual feature in this case.
Indian J Cancer 1992 Sep
PMID:Aniridia--Wilms' tumour association--a case with 11p 13-14.1 deletion and ventricular septal defect. 133 56

Wilms' tumour is rarely associated with sporadic non-familial congenital aniridia. A child with sporadic aniridia has a 25% chance of subsequently developing Wilms' tumour. Unawareness of this association can lead to a delayed diagnosis of Wilms' tumour. One such case in a 2 year old is reported. Wilms' tumour, one of the common childhood malignancies, is associated with other congenital anomalies in about 15% of cases. These include hemihypertrophy, genitourinary abnormalities, mental retardation, aniridia etc. Sporadic non-familial aniridia was noted in only 1.1% of 547 children with Wilms' tumours evaluated by the National Wilms' Tumour study group. Unawareness on the part of a clinician about these associated anomalies can lead to an avoidable delay in diagnosing Wilms' tumour. One such case in a two year old girl is being reported.
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PMID:Aniridia-Wilms' tumour syndrome--a case report. 133 31

Although radiation protection standards have changed remarkably little over the past decade, there have been changes in our understanding of radiation hazards that may affect the practice of radiation medicine over the next decade. With recognition of indoor radon exposure has come a new focus for public health concerns, because it is now clear that radon rather than medical exposure is the largest controllable source of radiation exposure to the general public. Continued follow-up of irradiated populations has led to an increase in our estimate of the cancer risk for high-dose exposures; this increased risk estimate is, in turn, leading to decreases in radiation exposure limits. Although our concern about the carcinogenic risk for radiation exposure has increased, our concern about genetic consequences has decreased, because no genetic effects have yet been observed in the offspring of atomic bomb survivors. Studies of atomic bomb survivors have also led to a change in the focus of concern over prenatal radiation exposure; the principle risk now appears to be mental retardation rather than childhood cancer.
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PMID:A decade of changes in radiation protection. 155 78

Radiation is a convenient tool to study fundamental processes of life. Biological effects of irradiation may result from indirect actions which are mediated by free radicals (e.g. OH-radicals) or from direct actions which involve ionizations in the DNA and other biomolecules. Damage to the DNA is the principal, but not exclusive target for cell death, loss of reproductive integrity, mutation, cancer, developmental anomalies and other radiobiological effects. Repair of damaged DNA and cellular recovery processes play an essential role in affecting the survival of cells. Dose, dose rate, radiation quality, biological and chemical modifiers also have a pronounced effect upon the extent of radiation responses. The biological effects of ionizing radiation are somatic or hereditary and can further be classified into stochastic and deterministic effects. For radiation epidemiology and protection the stochastic action is more relevant because the probability of an effect is a function of dose, without a threshold. Induction of cancer, hereditary diseases and probably also mental retardation are regarded as stochastic effects.
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PMID:Radiobiological fundamentals in radioepidemiology and radiation protection. 175 Feb 72

It is now known that chromosome disorders form a major category of genetic disease, accounting for a large proportion of all reproductive wastage, congenital malformations, and mental retardation, as well as playing an important role in the pathogenesis of malignancy. A variety of new techniques can be used to identify the chromosomal location of genes directly that promises to revolutionize the field of chromosomal analysis.
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PMID:[Diagnostic advances in chromosomal analysis]. 182 56


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