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Two cases of fragile X-syndrome are presented. Both boys had a family history of learning disability. This syndrome is the most common cause of inherited mental retardation. There are few dysmorphic features in childhood, but in puberty 80% of persons with this syndrome develop macro-orchidism, as presented in our second case. Some of the cases may have large ears, with no folding pinnea (simple pinnae). They may also have long faces, and a prominent forehead and chin. A characteristic of the condition is behavioural dysfunction, including hyperactivity and autism. The author discusses difficulties diagnosing the condition, both clinically and by specialized chromosome analysis.
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PMID:[Fragile X-syndrome and mental retardation]. 155 20

Developmental language and learning disabilities in children can take many different forms and can result from a variety of causes. Research to date has focused primarily on specific disabilities in learning, which are characterized by a significant delay or disorder in one aspect of learning against a background of otherwise normal development. Learning disabilities affecting language and/or reading acquisition (developmental dysphasia and dyslexia) have been studied most thoroughly. Verbal learning disabilities occur more frequently in boys than in girls, and there is a higher than expected incidence of left-handedness among affected children. Although there are many reasons why a child may have delayed or disordered language development, differential diagnosis of specific developmental language or reading disorders calls for ruling out mental retardation, peripheral auditory or visual dysfunction, autism, frank neurological impairments such as hemiplegia or seizure disorder, and severe social deprivation or lack of educational opportunity. The typical profile of a developmentally dysphasic or dyslexic child is one who shows a marked discrepancy between nonverbal (performance) IQ and verbal IQ, with a history of delayed or disordered speech, language and/or reading development. Such a child usually performs quite normally on visual spatial tasks, while demonstrating severe deficits in tasks of auditory temporal processing, motor sequencing, phonological processing and memory, language, reading and spelling. This characteristic neuropsychological profile may suggest left hemisphere dysfunction or a failure to develop normal cerebral lateralization. The etiology of these developmental learning disorders is unknown, but there is evidence of familial aggregation, indicating a potential genetic basis. Although these children respond to remediation, longitudinal studies have shown that the symptoms often persist into adulthood (see Tallal, 1988, for a more detailed discussion).
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PMID:Hormonal influences in developmental learning disabilities. 196 40

The composition of hyperactivity as a syndrome is discussed from a historical perspective, and the principal events leading to the recent emphasis on attentional characteristics of hyperactive children are summarized. Some of the major challenges to the legitimacy of hyperactivity as a valid syndrome are set forth, and after critical examination of the most influential work, it is concluded that hyperactivity has not been disproved. This is followed by a survey of the large follow-up literature dealing with the natural history of children diagnosed as hyperactive. It is noted that the manifestations of the syndrome appear to change with age but there is little indication that problems simply remit with maturity. The evidence indicates that hyperactivity, as diagnosed in the past, is often a serious disorder with long-term and far-reaching consequences for the children and their families. Multivariate studies are also discussed, as they have important implications for differential outcome. Different symptoms such as aggression, overactivity, and learning disability appear to contain unique information about current and future status, and therefore it appears useful to retain these distinctions rather than view such children as part of an undifferentiated group. It is unknown whether the recent guidelines for diagnosing Attention Deficit Disorder with Hyperactivity will alter or refine the outlook for children so identified, but this is an active area of research at present.
J Autism Dev Disord 1984 Mar
PMID:Hyperactivity: nature of the syndrome and its natural history. 636 21

Motor dysfunctions have been associated with learning disabilities in casual observation and systematic study. However, most prior work has concentrated solely on high-level skills and has been subject to observer bias. In this study, boys with learning disability were blindly compared with paired controls on measures of postural and equilibrium reflexes as well as skills. Learning-disabled children as a group showed significant deficits on all measures; a few, however, were totally without deficit. The implications of these findings for controversies about the role of motor dysfunction in learning disabilities are examined.
J Autism Dev Disord 1980 Jun
PMID:Blind evaluation of body reflexes and motor skills in learning disability. 692 84

Although tuberous sclerosis is associated severe learning disability, it is also a physical disorder with growths that affect any part of the body. Recent genetic research explains the diversity of the condition. The behavioural phenotype of tuberous sclerosis has shown the autism and attention deficit disorder associated with the brain lesions.
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PMID:Gaining new understanding of tuberous sclerosis. 766 26

A genetic etiology in autism is now strongly supported by family and twin studies. A 3:1 ratio of affected males to females suggests the involvement of at least one X-linked locus in the disease. Several reports have indicated an association of the fragile X chromosomal anomaly at Xq27.3 (FRAXA) with autism, whereas others have not supported this finding. We have so far collected blood from 105 simplex and 18 multiplex families and have assessed 141 patients by using the Autism Diagnostic Interview-Revised (ADI-R), the Autism Diagnostic Observation Scale, and psychometric tests. All four ADI-R algorithm criteria were met by 131 patients (93%), whereas 10 patients (7%) showed a broader phenotype of autism. Southern blot analysis was performed with three different enzymes, and filters were hybridized to an FMR-1-specific probe to detect amplification of the CCG repeat at FRAXA, to the complete FMR-1 cDNA probe, and to additional probes from the neighborhood of the gene. No significant changes were found in 139 patients (99%) from 122 families, other than the normal variations in the population. In the case of one multiplex family with three children showing no dysmorphic features of the fragile X syndrome (one male meeting 3 out of 4 ADI-algorithm criteria, one normal male with slight learning disability but negative ADI-R testing, and one fully autistic female), the FRAXA full-mutation-specific CCG-repeat expansion in the genotype was not correlated with the autism phenotype. Further analysis revealed a mosaic pattern of methylation at the FMR-1 gene locus in the two sons of the family, indicating at least a partly functional gene. Therefore, we conclude that the association of autism with fragile X at Xq27.3 is non-existent and exclude this location as a candidate gene region for autism.
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PMID:Molecular genetic analysis of the FMR-1 gene in a large collection of autistic patients. 925 54

BACKGROUND AND AIM OF REVIEW. In 1991, the gene responsible for fragile X syndrome, a common cause of learning disability, was discovered. As a result, diagnosis of the disorder has improved and its molecular genetics are now understood. This report seems to provide the information needed to decide whether to use DNA testing to screen for the disorder. HOW THE RESEARCH WAS CONDUCTED. A literature search of electronic reference databases of published and 'grey' literature was undertaken together with hand searching of the most recent publications. RESEARCH FINDINGS. NATURAL HISTORY. Physical characteristics of fragile X syndrome include facial atypia, joint laxity and, in boys, macro-orchidism. Most affected males have moderate-to-severe learning disabilities with IQs under 50 whereas most females have borderline IQs of 70-85. Behavioural problems are similar to those seen with autism and attention-deficit disorders. Although fragile X syndrome is not curable there are a number of medical, educational, psychological and social interventions that can improve the symptoms. About 6% of those with learning disabilities tested in institutions have fragile X syndrome. Population prevalence figures are 1 in 4000 in males and 1 in 8000 in females. GENETICS. The disorder is caused by a mutation in a gene on the X chromosome which includes a trinucleotide repeat sequence. The mutation is characterized by hyper-expansion of the repeat sequence leading to down-regulation of the gene. In males an allele with repeat size in excess of 200, termed a full mutation (FM), is always associated with the affected phenotype, whereas in females only half are affected. Individuals with alleles having repeat size in the range 55-199 are unaffected but in females the sequence is heritably unstable so that it is at high risk of expansion to an FM in her offspring. This allele is known as a pre-mutation (PM) to contrast it with the FM found in the affected individual. No spontaneous expansions directly from a normal allele to an FM have been observed. SCREENING STRATEGIES. The principal aims of screenng for fragile X syndrome is to reduce the birth prevalence of the disorder, by prenatal diagnosis and selective termination of pregnancy, or by reducing the number of pregnancies in women who have the FM or PM alleles. Possible screening strategies are: routine antenatal testing of apparently low risk pregnancies, preconceptual testing of young women, and systematic testing in affected families ('cascade' screening). A secondary aim is to bring forward the diagnosis of affected individuals so that they might benefit from early treatment. Active paediatric screening and neonatal screening could achieve this but there is no direct evidence of any great benefit from early diagnosis. SCREENING TESTS. Cytogenetic methods are unsuitable for screening purposes. Southern blotting of genomic DNA can be used but is inaccurate in measuring the size of small PMs, there is a long laboratory turnaround time, and it is relatively expensive. The best protocol is to amplify the DNA using polymerase chain reaction on all samples, and when there is a possible failure to amplify, a Southern blot.(ABSTRACT TRUNCATED)
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PMID:Screening for fragile X syndrome. 941 43

Autism is an organic disorder affecting several areas of a child's development. Autism is present from birth, or very soon after, but the nature of the disorder can mean that diagnosis is delayed for months for years. Early intervention can improve long-term function and help the families. Babies with autism may display characteristic features of gaze, hearing, social development and play. Nurses working with babies and young children are in a prime position to recognise these characteristics and refer the family for specialised assessment. Learning disabilities may or may not be present in children with autism. Always listen to the parents. They often suspect something is wrong even though they may not be able to be precise.
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PMID:Autism: recognising the signs in young children. 1019 15

Autism and Rett syndrome (RS) are both developmental disorders of unknown origin. Autism is a behaviourally defined syndrome. RS, which affects girls only, is characterized by a profound learning disability following early normal development, with a consistent cluster of clinical features. Differentiation of RS from infantile autism in the very early stages of the disorders is not always easy. Both syndromes still lack discriminative laboratory markers for accurate diagnosis and differentiation. We decided to compare the CSF nerve-growth factor (NGF) levels of children with infantile autism and children with RS using enzyme-linked immunosorbent assay (ELISA). Our findings of mainly normal CSF NGF in autism and low to negligible values in RS are in agreement with the different morphological and neurochemical findings (brain growth, affected brain areas, neurotransmitter metabolism) in the two syndromes. CSF NGF could be used as a biochemical marker for differentiation of patients with autism from those with RS.
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PMID:Levels of cerebrospinal fluid nerve-growth factor differ in infantile autism and Rett syndrome. 1021 Feb 46

Learning disabilities, intellectual retardation, dyslexia, attention deficit/hyperactivity disorder, autism, and propensity to violence affect millions of U.S. citizens and are diagnosed in an estimated 3% of all children born in the United States. The consequences of these neurological, developmental, and behavioral disorders are often tragic; their familial, societal, and economic costs are immense, and the resulting disabilities lifelong. Toxic chemicals in the environment--lead, polychlorinated biphenyls, mercury, and certain pesticides--are now known to cause some fraction of neurodevelopmental disabilities. The implications of this discovery for prevention are potentially enormous; developmental disorders of toxic origin can, in theory, be prevented through the identification, characterization, and elimination of toxic environmental exposures. However, serious impediments to prevention exist: too few chemicals are tested for toxicity to early brain development, knowledge of infants' and children's special vulnerabilities and unique exposures is scant, and paradigms for environmental risk assessment have only begun to address the hazards confronting infants and children.
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PMID:A research-oriented framework for risk assessment and prevention of Children's exposure to environmental toxicants 1033 54


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