Fragile X syndrome

New Animal Models for Understanding FMRP Functions and FXS Pathology

Fragile X encompasses a range of genetic conditions, all of which result as a function of changes within the FMR1 gene and abnormal production and/or expression of the FMR1 gene products. Individuals with Fragile X syndrome (FXS), the most common heritable form of intellectual disability, have a full-mutation sequence (>200 CGG repeats) which brings about transcriptional silencing of FMR1 and loss of FMR protein (FMRP). Despite considerable progress in our understanding of FXS, safe, effective, and reliable treatments that either prevent or reduce the severity of the FXS phenotype have not been approved. While current FXS animal models contribute their own unique understanding to the molecular, cellular, physiological, and behavioral deficits associated with FXS, no single animal model is able to fully recreate the FXS phenotype. This review will describe the status and rationale in the development, validation, and utility of three emerging animal model systems for FXS, namely the nonhuman primate (NHP), Mongolian gerbil, and chicken. These developing animal models will provide a sophisticated resource in which the deficits in complex functions of perception, action, and cognition in the human disorder are accurately reflected and aid in the successful translation of novel therapeutics and interventions to the clinic setting.

Dietary rescue of adult behavioral deficits in the Fmr1 knockout mouse

The current study aimed to further address important questions regarding the therapeutic efficacy of omega-3 fatty acids for various behavioral and neuroimmune aspects of the Fmr1 phenotype. To address these questions, our experimental design utilized two different omega-3 fatty acid administration timepoints, compared to both standard laboratory chow controls ("Standard") and a diet controlling for the increase in fat content ("Control Fat"). In the first paradigm, post-weaning supplementation (after postnatal day 21) with the omega-3 fatty acid diet ("Omega-3") reversed deficits in startle threshold, but not deficits in prepulse inhibition, and the effect on startle threshold was not specific to the Omega-3 diet. However, post-weaning supplementation with both experimental diets also impaired acquisition of a fear response, recall of the fear memory and contextual fear conditioning compared to the Standard diet. The post-weaning Omega-3 diet reduced hippocampal expression of IL-6 and this reduction of IL-6 was significantly associated with diminished performance in the fear conditioning task. In the perinatal experimental paradigm, the Omega-3 diet attenuated hyperactivity and acquisition of a fear response. Additionally, perinatal exposure to the Control Fat diet (similar to a "Western" diet) further diminished nonsocial anxiety in the Fmr1 knockout. This study provides significant evidence that dietary fatty acids throughout the lifespan can significantly impact the behavioral and neuroimmune phenotype of the Fmr1 knockout model.

Inequities in diagnosis of Fragile X syndrome in Colombia

BACKGROUND

Fragile X syndrome (FXS) is the most common cause of inherited intellectual disability and autism spectrum disorder (ASD). In Colombia, there are no screening or testing protocols established for the diagnosis of FXS. In this study, we aimed to describe the diagnostic trends of FXS in Colombia.

METHODS

Data were included on 1322 individuals obtained based on data from the only 2 databases available. Sociodemographic information and data related to the diagnostic process were obtained and included in this study.

RESULTS

The average age at the time of diagnosis for individuals with the full mutation (FM) was of 26.9 ± 2.57 years and was strongly dependent on sex and socioeconomic status. Most individuals with a molecular diagnosis were from the main cities.

CONCLUSION

The overall age of diagnosis of FXS is later in life than reports from other countries. Restricted access to molecular testing through the national health system might explain this discrepancy in Colombia.

Utility of the Hebb-Williams Maze Paradigm for Translational Research in Fragile X Syndrome: A Direct Comparison of Mice and Humans

To generate meaningful information, translational research must employ paradigms that allow extrapolation from animal models to humans. However, few studies have evaluated translational paradigms on the basis of defined validation criteria. We outline three criteria for validating translational paradigms. We then evaluate the Hebb–Williams maze paradigm (Hebb and Williams, 1946; Rabinovitch and Rosvold, 1951) on the basis of these criteria using Fragile X syndrome (FXS) as model disease. We focused on this paradigm because it allows direct comparison of humans and animals on tasks that are behaviorally equivalent (criterion #1) and because it measures spatial information processing, a cognitive domain for which FXS individuals and mice show impairments as compared to controls (criterion #2). We directly compared the performance of affected humans and mice across different experimental conditions and measures of behavior to identify which conditions produce comparable patterns of results in both species. Species differences were negligible for Mazes 2, 4, and 5 irrespective of the presence of visual cues, suggesting that these mazes could be used to measure spatial learning in both species. With regards to performance on the first trial, which reflects visuo-spatial problem solving, Mazes 5 and 9 without visual cues produced the most consistent results. We conclude that the Hebb–Williams mazes paradigm has the potential to be utilized in translational research to measure comparable cognitive functions in FXS humans and animals (criterion #3).

Loss of FMRP Impaired Hippocampal Long-Term Plasticity and Spatial Learning in Rats

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by mutations in the FMR1 gene that inactivate expression of the gene product, the fragile X mental retardation 1 protein (FMRP). In this study, we used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology to generate Fmr1 knockout (KO) rats by disruption of the fourth exon of the Fmr1 gene. Western blotting analysis confirmed that the FMRP was absent from the brains of the Fmr1 KO rats (Fmr1^exon4-KO ). Electrophysiological analysis revealed that the theta-burst stimulation (TBS)-induced long-term potentiation (LTP) and the low-frequency stimulus (LFS)-induced long-term depression (LTD) were decreased in the hippocampal Schaffer collateral pathway of the Fmr1^exon4-KO rats. Short-term plasticity, measured as the paired-pulse ratio, remained normal in the KO rats. The synaptic strength mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) was also impaired. Consistent with previous reports, the Fmr1^exon4-KO rats demonstrated an enhanced 3,5-dihydroxyphenylglycine (DHPG)-induced LTD in the present study, and this enhancement is insensitive to protein translation. In addition, the Fmr1^exon4-KO rats showed deficits in the probe trial in the Morris water maze test. These results demonstrate that deletion of the Fmr1 gene in rats specifically impairs long-term synaptic plasticity and hippocampus-dependent learning in a manner resembling the key symptoms of FXS. Furthermore, the Fmr1^exon4-KO rats displayed impaired social interaction and macroorchidism, the results consistent with those observed in patients with FXS. Thus, Fmr1^exon4-KO rats constitute a novel rat model of FXS that complements existing mouse models.

Role of Genetics in the Etiology of Autistic Spectrum Disorder: Towards a Hierarchical Diagnostic Strategy

Progress in epidemiological, molecular and clinical genetics with the development of new techniques has improved knowledge on genetic syndromes associated with autism spectrum disorder (ASD). The objective of this article is to show the diversity of genetic disorders associated with ASD (based on an extensive review of single-gene disorders, copy number variants, and other chromosomal disorders), and consequently to propose a hierarchical diagnostic strategy with a stepwise evaluation, helping general practitioners/pediatricians and child psychiatrists to collaborate with geneticists and neuropediatricians, in order to search for genetic disorders associated with ASD. The first step is a clinical investigation involving: (i) a child psychiatric and psychological evaluation confirming autism diagnosis from different observational sources and assessing autism severity; (ii) a neuropediatric evaluation examining neurological symptoms and developmental milestones; and (iii) a genetic evaluation searching for dysmorphic features and malformations. The second step involves laboratory and if necessary neuroimaging and EEG studies oriented by clinical results based on clinical genetic and neuropediatric examinations. The identification of genetic disorders associated with ASD has practical implications for diagnostic strategies, early detection or prevention of co-morbidity, specific treatment and follow up, and genetic counseling.

Are females more variable than males in gene expression? Meta-analysis of microarray datasets

Background

The majority of preclinical biomedical research involves studies of males rather than females. It is thought that researchers have avoided females based on the idea that female traits are more variable than those of males because of cyclic variation in effects of ovarian hormones.

Methods

To test the assumption of inherently greater female variability, we analyzed 293 microarray datasets measuring gene expression in various tissues of mice and humans, comprising analysis of more than 5 million probes.

Results

Meta-analysis showed that on average, male gene expression is slightly more variable than that of females although the difference is small. We also tested if the X chromosome of humans shows greater variability in gene expression in males than in females, as might be expected because of hemizygous exposure of polymorphic X alleles but again found little sex difference.

Conclusion

Our analysis supports and extends previous studies reporting no overall greater phenotypic variability in females.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-015-0036-8) contains supplementary material, which is available to authorized users.

Genetic Counseling for Fragile X Syndrome: Recommendations of the National Society of Genetic Counselors

The National Society of Genetic Counselors' (NSGC) recommendations for fragile X syndrome (FXS) genetic counseling are intended to assist health care professionals who provide genetic counseling for individuals and families in whom the diagnosis of FXS is strongly suspected or has been made. The recommendations are the opinions of genetic counselors with expertise in FXS counseling and are based on clinical experience, a review of pertinent English language medical articles, and reports of expert committees. These recommendations should not be construed as dictating an exclusive course of management, nor does use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a particular client.

Emotion potentiated startle in fragile X syndrome

Social avoidance and anxiety are prevalent in fragile X syndrome (FXS) and are potentially mediated by the amygdala, a brain region critical for social behavior. Unfortunately, functional brain resonance imaging investigation of the amygdala in FXS is limited by the difficulties experienced by intellectually impaired and anxious participants. We investigated the relationship between social avoidance and emotion-potentiated startle, a probe of amygdala activation, in children and adolescents with FXS, developmental disability without FXS (DD), and typical development. Individuals with FXS or DD demonstrated significantly reduced potentiation to fearful faces than a typically developing control group (p < .05). However, among individuals with FXS, social avoidance correlated positively with fearful-face potentiation (p < .05). This suggests that general intellectual disability blunts amygdalar response, but differential amygdala responsiveness to social stimuli contributes to phenotypic variability among individuals with FXS.

ASD, ADHD, mental health conditions and psychopharmacology in neurogenetic syndromes: parent survey

BACKGROUND

There are a number of neurogenetic syndromes with well described behavioural phenotypes including fragile X syndrome, Prader-Willi syndrome, Williams syndrome and velo-cardio-facial syndrome (VCFS). Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and psychiatric conditions are often associated with the syndromes.

METHOD

Parents (n = 381) of school-aged children with one of the four syndromes in the UK and Ireland were asked whether their child had been professionally diagnosed with ASD, ADHD or a mental health condition. Parents were also asked whether their child had been prescribed medication for behavioural or psychiatric reasons.

RESULTS

The highest level of reported diagnoses of ASD and ADHD was in fragile X syndrome. In all syndrome groups, lower rates of diagnosis were reported in comparison to previously published research. Prescribing of medication for behavioural/psychiatric reasons was highest in fragile X syndrome although the highest usage of melatonin was in Williams syndrome.

CONCLUSION

Reasons for a lower recognition of ASD, ADHD and mental health conditions in clinical practice compared with research studies may include 'diagnostic overshadowing' due to presence of intellectual disability and a genetic syndrome. However, there may also be a lack of belief in the utility of such diagnoses in neurogenetic syndromes among relevant professionals and/or lack of access to professionals with sufficient expertise in the recognition of such diagnoses in those with neurogenetic syndromes. The low rates of prescribing of medication for behavioural/psychiatric reasons may reflect the low level of clinical diagnoses or lack of belief in the utility of psychopharmacology in this population.

Behavioural phenotypes and special educational needs: is aetiology important in the classroom?

BACKGROUND

A number of genetic conditions with associated intellectual disability and/or special educational needs have increasingly well-defined behavioural phenotypes. Thus, the concept of 'behavioural phenotype' and aetiology of intellectual disability may be important with regard to school-based interventions.

METHOD

The evidence for distinctive cognitive and behavioural aspects of five of the most common genetic syndromes (Down syndrome, fragile X syndrome, Williams syndrome, Prader-Willi syndrome and velo-cardio-facial syndrome) associated with special educational needs is reviewed with respect to key studies and findings. The possible utility of aetiology-related interventions in education is discussed with reference to arguments for and against such approaches with respect to published guidelines and published research.

RESULTS

Behavioural phenotypes are probabilistic and many children with a specific genetic syndrome will share commonalities with other children with other genetic syndromes and within syndrome variability is not uncommon. There is evidence that teachers and parents have limited knowledge of aspects of the proposed cognitive and behaviour profiles associated with the reviewed syndromes. While there are published guidelines in the area of learning and behaviour for each of the five reviewed syndromes there is a limited amount of evidence of the efficacy of such approaches in school settings.

CONCLUSION

It is likely that knowing the aetiology of a child's special educational needs will be helpful for staff who work in school settings in relation to cognitive and behavioural implications. However, how such knowledge might inform teaching practice or behavioural interventions has not been studied. A model is proposed that might help inform educators about the possible role of aetiology in the classroom.

Evaluation of clinical checklists for fragile X syndrome screening in Brazilian intellectually disabled males: proposal for a new screening tool

Patients with fragile X syndrome present a variable phenotype, which contributes to the underdiagnosing of this condition. The use of clinical checklists in individuals with intellectual disability can help in selecting patients to be given priority in the molecular investigation of the fragile X mutation in the FMR1 gene. Some features included in checklists are better predictors than others, but they can vary among different populations and with patient age. In the present study, we evaluated 20 features listed in four clinical checklists from the literature, using a sample of 192 Brazilian male patients presenting with intellectual disability (30 positive and 162 negative for fragile X mutation). After statistical analysis, 12 out of the 20 items analyzed showed significant differences in their distributions between the two groups. These features were grouped in a new checklist that can help clinicians in their referral for fragile X testing in patients with developmental delay.

Speech fluency in fragile X syndrome

The present study investigated the dysfluencies in the speech of nine French speaking individuals with fragile X syndrome. Type, number, and loci of dysfluencies were analysed. The study confirms that dysfluencies are a common feature of the speech of individuals with fragile X syndrome but also indicates that the dysfluency pattern displayed is not identical to developmental stuttering. To what extent the pattern of dysfluency in individuals with fragile X syndrome is syndrome specific is not yet clear.

Fluency disorders in genetic syndromes

The characteristics of various genetic syndromes have included "stuttering" as a primary symptom associated with that syndrome. Specifically, Down syndrome, fragile X syndrome, Prader-Willi syndrome, Tourette syndrome, Neurofibromatosis type I, and Turner syndrome all list "stuttering" as a characteristic of that syndrome. An extensive review of these syndromes indicated clients diagnosed with these syndromes do show evidence of nonfluency patterns, but not all would be considered stuttering. Many of the syndromes are marked by degrees of mental retardation that probably contribute to a higher than average prevalence of stuttering, as well as a higher than average prevalence of other fluency disorders (when compared to the population at large). An in-depth analysis of the available data indicates that some of these genetic syndromes show patterns of stuttering that may be indicative of only that syndrome (or similar syndromes) that can be differentially diagnosed from developmental stuttering. Among these patterns are the word-final nonfluencies noted in Prader-Willi syndrome; the presence of stuttering in the absence of secondary behaviors noted in Prader-Willi syndrome and; the presence of palilalia, word-final and word-medial nonfluencies, and word-medial and word-final nonfluencies in Tourette syndrome. Implications for future research are discussed in light of these findings.

EDUCATIONAL OBJECTIVES

The reader will be able to: (1) describe the various different genetic syndromes that are associated with fluency disorders; (2) describe the types of nonfluencies that are associated with the major types of genetic syndromes that have fluency disorders; (3) describe the behaviors that may assist in differentially diagnosing different types of speech characteristics associated with various genetic syndromes.

Annotation: Deconstructing the attention deficit in fragile X syndrome: a developmental neuropsychological approach

BACKGROUND

Fragile X syndrome is one of the world's leading hereditary causes of developmental delay in males. The past decade has witnessed an explosion of research that has begun to unravel the condition at its various levels: from the genetic and brain levels to the cognitive level, and then to the environmental and behavioural levels. Our aim in this review is to attempt to integrate some of the extensive body of knowledge to move the research a step closer to understanding how the dynamics of atypical development can influence the specific cognitive and behavioural end-states frequently observed in children and adolescents with fragile X syndrome.

METHODS

We conducted a review of the current neuropsychological and neuropsychiatric approaches that have attempted to delineate the pattern of 'spared' and 'impaired' functions associated with the phenotype.

RESULTS

The profile of findings suggests that fragile X syndrome should not be viewed merely as a catalogue of spared and impaired cognitive functions or modules. Instead, there appears to be a process of almost gradual modularisation whereby cognitive mechanisms become domain specific as a function of development itself (Karmiloff-Smith, 1992). The results of a decade of intense research point towards an early weakness in one or more components of executive control rather than single, static higher-level deficits (e.g., spatial cognition, speech processing). This weakness affects both the development of more complex functions and current performance.

CONCLUSIONS

The prevailing tendency to interpret developmental disorders in terms of fixed damage to distinct modular functions needs to be reconsidered. We offer this review as an example of an alternative approach, attempting to identify an initial deficit and its consequences for the course of development. Through better definition of the cognitive and behavioural phenotype, in combination with current progress in brain imaging techniques and molecular studies, the next decade should continue to hold exciting promise for fragile X syndrome and other neurodevelopmental disorders.

Further delineation of the executive deficit in males with fragile-X syndrome

This paper presents a detailed analysis of one aspect of performance by young males with fragile-X syndrome (FMR-1 full mutation) who were assessed on a computerised visual search task as part of a larger study examining aspects of attention [Neuropsychologia 38 (2000) 1261]. They were matched on chronological and mental age to 25 boys with Down's syndrome (trisomy 21) and on mental age to 50 mainstream school boys (controls). The controls were further divided into those matched on "poor attention" to the fragile-X boys and a "good" attention group, as rated by the comprehensive teacher rating scale (ACTeRS) questionnaire. Both fragile-X and Down's syndrome boys made significantly more repeated responses on targets (but a lower proportion of errors based on confusion of shape) than the two control groups and these differences were stronger in the fragile-X group. In the single target condition, search was for a single type of target throughout. In the dual target condition, participants were required to alternate between two different targets. Fragile-X boys showed significantly greater inability than Down's syndrome and normal boys to switch attention between targets and both learning-disabled groups were inferior to the control groups. Thus, both learning-disabled groups displayed a weakness in inhibiting repetition and in switching attention from one type of target to another and the impairments were more acute in fragile-X boys. The results provide further support for an attention deficit in this population at higher levels of attention control/executive functioning that involve switching visual attention and inhibiting repetitious behaviour.

A neuropsychological profile of attention deficits in young males with fragile X syndrome

Different processes of attention were examined in a group of 25 fragile X boys with FMR-1 full mutation and compared with three control groups: a learning disabled comparison group comprising 25 boys with Down's syndrome, matched to the fragile X boys on verbal mental age; and 50 mainstream school boys (controls) matched to the fragile X boys on verbal mental age. The controls were further divided into those matched on "poor attention" to the fragile X boys and a "good" attention group, as rated by the ACTeRS questionnaire. Four categories of attention tasks were employed: selective attention, divided attention, sustained attention and executive functioning. The main findings of the study indicate that fragile X boys display an attention deficit at higher levels of attention function/executive functioning and that this profile is different from the profile identified in Down's syndrome boys and more extreme than the profile identified in the poor attention control group. These findings are discussed in the context of functional neuroimaging and brain-behaviour correlates in fragile X syndrome.

Fragile-X syndrome, Down's syndrome and autism: awareness and knowledge amongst special educators

Fragile-X syndrome is the commonest cause of inherited intellectual disability. There is good evidence for a behavioural phenotype. This has implications for school staff using standard educational techniques. Similarly, autism is known to create particular educational requirements. The present study examined the awareness and knowledge of fragile-X syndrome, Down's syndrome and autism amongst staff in special and mainstream education. One hundred and two special school staff and 40 mainstream school staff completed questionnaires. Most staff offered a variety of features 'typical' of Down's syndrome and autism. In contrast, staff knew less about fragile-X syndrome. Specific knowledge about the learning styles of these children was very poor, but was associated with having taught an affected child. Mainstream and special school staff offered similar levels of knowledge for all three conditions. Staff did not demonstrate a sufficiently specialized knowledge of fragile-X syndrome to ensure that the special educational needs of these children were being met fully.

Fragile X syndrome. Clinical and cytogenetic studies

Three families with the fragile X syndrome were studied with the aim to establish the most frequent clinical signs in the affected individuals and heterozygous women. The clinical evaluation, IQ level measurements and cytogenetic studies were performed in 40 subjects, 20 males and 20 females. The fragile X diagnosis was confirmed in all the male individuals with mental retardation. In the postpubertal subjects the most frequent clinical signs were inner canthal distance < 3.5 cm, macro-orchidism, long and narrow face and high arched palate while in the prepubertal subjects the behavioral characteristics as hyperactivity and poor eye contact were the most frequent and were observed in all patients. Twenty six percent of the heterozygous women presented with mental retardation and showed clinical signs rather than behavioral ones. All male individuals with mental retardation were observed as having fragile X [fra(X)] in lymphocytes culture. Sixty three percent of women showed fra(X). There was a positive correlation between the frequency of fra(X) and the clinical characteristics. We emphasize the importance of the clinical evaluation in the study of familial mental retardation and in the screening of isolated cases with suspect of having the fragile X syndrome.

Molecular genetic analysis of mentally retarded males with features of the fragile-X syndrome

The fragile-X[fra(X)] or Martin-Bell syndrome is the most common familial cause of mental retardation and is characterized by the presence of an Xq27.3 chromosome fragile site. Unstable DNA sequences representing large increases in the number of CGG trinucleotide DNA base repeats of the FMR-1 gene are located at the fragile site and responsible for the fra(X) syndrome. In order to identify whether cytogenetically normal yet mentally retarded males without a known cause of their retardation had expansion of the CGG repeat segment of the FMR-I gene, molecular genetic studies using Southern hybridization were performed with two DNA probes (fxa241 and Ox1.9) following digestion of genomic DNA from each patient with restriction enzymes Pstl and EcoRl/Eagl, respectively. DNA studies were performed on 20 (12.3%) out of 162 (122 white and 40 black people) cytogenetically normal mentally retarded males without a known cause of their retardation, but with high anthropometric discriminant values and/or clinical checklist scores identified previously and consistent with the fra(X) syndrome. None of the 20 males showed expansion of the CGG repeat of the FMR-1 gene detectable with the two probes used in this study. While heterogeneous single base pair substitutions, or small deletions or insertions in the FMR-I gene could exist in our patients, aberrations in other X-linked mental retardation genes, not identified to date but whose gene product can produce a phenotype similar to fra(X), either independently or in conjunction with the recently identified FMR-I protein, should be considered and are under investigation. Our study supports the idea that major FMR-I gene expansion detectable with Southern hybridization is rare in cytogenetically normal mentally retarded males, including those with physical and behavioural features seen in the fra(X) syndrome.

Cognitive functioning and information processing of adult mentally retarded men with fragile-X syndrome

The present study describes cognitive skills and information processing strategies of mentally retarded fra(X) men. Fifty-eight fra(X) positive and 58 fra(X) negative adults, matched on sex, chronological age, length of institutionalisation, general cognitive level, and living conditions, were evaluated with the Bayley or McCarthy Scales of Mental Abilities. Mental ages were mostly situated in the severe mental handicap category and were found to be negatively influenced by chronological age. A relative strength in perceptual performance and non-verbal reasoning and a deficit in sequential information processing turned out to be typical of all mentally retarded subjects, irrespective of fra(X) or control status. Fra(X) adults could be significantly differentiated from control persons on the ground of a higher level of acquired knowledge because of better vocabulary and verbal-expressive skills. On the other hand, they were less able to imitate non-verbal patterns, had more difficulty with visual-motor integration and co-ordination, and applied less efficient general mental processing skills in solving new problems. The memory profile of fra(X) adults was strongly determined by the meaning and the complexity of the information that has to be reproduced. In this article the profile of cognitive strengths and weaknesses in the fra(X) group will be discussed and some general advice for training is suggested.

The psychiatric, psychological and behavioural functioning of a boy with terminal deletion of the long arm of chromosome 10

The developmental and behavioural functioning of a six-year-old boy with deletion of the long arm of chromosome 10 was evaluated using reliable, standardised, psychological inventories. The information obtained clarified his complex pattern of strengths and needs; it also contributes scientifically derived data to the literature on behavioural correlates of this condition.

Clinical and cytogenetic survey of institutionalized mentally retarded patients with emphasis on the fragile-X syndrome

A detailed clinical and cytogenetic survey for the fragile-X syndrome was undertaken on 201 institutionalized mentally retarded males with no previously recognized cause of retardation, and the causes of mental retardation were summarized from a total of 595 institutionalized male and female patients after the review of their medical records including clinical and cytogenetic data. Among the 201 males clinically and cytogenetically examined, five (2.5%) had abnormal chromosome findings with four (2%) having the fragile-X syndrome. Twelve of the males (6.0%) were diagnosed with a single gene disorder. In the present study, mental retardation was classified as possibly due to multifactorial causes when a genetic syndrome, chromosome abnormality or environmental insult was not identified, but mental retardation was present in one or more first and/or second degree relatives, but did not follow a recognizable inheritance pattern. Hence, mental retardation was recorded in other family members and may indicate possible multifactorial causes in 45 males (22.4%). An environmental insult was noted in 25 males (12.4%); unexplained birth defects in three males (1.5%); a specific condition or diagnosis identified, but cause unknown (e.g. Rubinstein-Taybi syndrome) in 10 males (5%); and no diagnosis made in the remaining 101 males (50.2%). Of all 595 patients (334 males and 261 females), including the 201 males who had undergone a detailed clinical and cytogenetic evaluation, 39 (6.6%) had abnormal chromosome findings, with Down's syndrome noted in 31 of the patients. Twenty-five patients (4.2%) were diagnosed with a single gene disorder while mental retardation was noted in other family members and may indicate possible multifactorial causes in 64 patients (10.8%). An environmental insult was noted in 170 patients (28.6%); unexplained birth defects in 17 patients (2.9%); a specific condition or diagnosis but cause unknown in 27 patients (4.5%); and no diagnosis made in 253 patients (42.5%). Clinical and cytogenetic screening of mentally retarded patients for the fragile-X syndrome and other causes of mental retardation is helpful in identifying individuals and their families who may benefit from genetic services such as counseling and treatment. This study was performed over an approximate 2 year period from 1987 to 1989.

Problem solving limitations among cytogenetically expressing fragile X women

Neurocognitive deficits among fragile X individuals have been reported for both high and low functioning individuals. Recent findings from our research suggest a specific neurocognitive phenotype among fragile X women that is characterized by deficits on tests of frontal lobe functioning. In this paper, we examine in more detail the performance of 10 cytogenetically expressing women and 10 control women on 2 problem solving measures considered sensitive to frontal lobe functions: the Contingency Naming Test and the Tower of Hanoi. The results pertaining to each test suggest that fragile X women, relative to control women, are less able to solve a problem when the difficulty of the problem is increased by requiring simultaneous consideration of additional information. These findings have important implications for remediation strategies designed for affected fragile X individuals.

The fragile-X syndrome. On the way to a behavioural phenotype

The fragile-X syndrome accounts for up to 10% of individuals with mental handicap, and 50% of cases of X-linked mental retardation. Knowledge of the genetic basis of mental functioning, psychopathology, and neuropsychology is being furthered by this recently recognised condition. The disorder has considerable significance for psychiatrists, particularly, but by no means exclusively, those working in the field of mental handicap and with children. This review outlines the slow clarification of this complex and important behavioural phenotype and the implications of these advances for identification, diagnosis, genetic counselling and a wide range of management interventions.

Changing patterns of intellectual strengths and weaknesses in males with fragile X syndrome

Examined the changing profiles of intelligence in males with fragile X syndrome as these individuals increased in chronological age. Using a psychometric instrument designed to measure styles of information processing, 21 males aged 4 to 27 years were examined cross-sectionally in sequential processing, simultaneous processing, and achievement. The age of the subject was associated with age-equivalent levels of both simultaneous processing and achievement, but fragile X males did not show higher levels of sequential processing with increasing chronological age. Compared to younger fragile X males, the older subjects were more delayed in sequential processing skills relative to their in other areas. A smaller longitudinal study confirmed the presence of a plateau in sequential processing among those subjects tested two times after the age of 10 years. Implications are discussed for diagnosis, intervention, and the matching of subject groups in mental retardation research.

Association of the Robin sequence with the fragile X syndrome

We report on 4 individuals with the fragile X [fra(X)] syndrome and the Robin sequence (or elements of that sequence). To our knowledge, this association has been described in only one other boy. However, males with the fra(X) syndrome have been reported to have an increased incidence of cleft palate. We recommend that children with a cleft palate or the Robin sequence be assessed for developmental delays and a family history of mental retardation. The fra(X) syndrome may be one of the genetic causes of the Robin sequence and, when indicated, children with the sequence should be tested for fra(X).

Anthropometric comparison of mentally retarded males with and without the fragile X syndrome

An anthropometric survey of 41 variables (weight, height, 10 linear, 4 breadth, 22 craniofacial, 2 skinfold, and testicular volume), including multivariate discriminant analysis, was undertaken on 110 mentally retarded males (39 with and 71 without the fra(X) syndrome). The mean Z scores of the fra(X) syndrome males fell between -2.00 and 8.38 for bizygomatic diameter and testicular volume, respectively, and the range of the mean Z scores of the non-fra(X) males was from -2.64 to 2.26 for hand breadth and testicular volume, respectively. There was a statistically significant difference (P less than .05) between fra(X) and non-fra(X) males for 18 measurements (weight, height, 7 linear, 2 breadth, 5 craniofacial, 1 skinfold, and testicular volume), with the greater measurements (excluding bizygomatic diameter) found in fra(X) males. Sitting height, knee-buttock length, middle finger length, and hand length were negatively correlated (P less than .05) with age, whereas bizygomatic diameter, ear length, and ear width were positively correlated (P less than .05) with age and head circumference, head length, and outer canthal distance were positively correlated (P less than .05) with fra(X) chromosome expression in the fra(X) males. Triceps and subscapular skinfold thicknesses were negatively correlated (P less than .05) with age, whereas ankle breadth, ear length, ear width, and nose length were positively correlated (P less than .05) in the non-fra(X) males. Discriminant analysis of 34 fra(X) and 71 non-fra(X) males resulted in a discriminant function based on 6 of 17 anthropometric variables and age.(ABSTRACT TRUNCATED AT 250 WORDS)

Major depressive disorder as a prominent but underestimated feature of fragile X syndrome

Three unrelated institutionalized mentally retarded males with fragile X syndrome presented major depressive disorders. Their depressive moods were long unrecognized because of the difficulties in assessing depressive symptoms in mentally retarded individuals. The genetic implications of establishing the diagnosis of this common heritable X-chromosome abnormality and the therapeutic consequences of detecting the depression are emphasized. Fragile X [fra(X)] may be a genetic predisposition to neuropsychiatric disorders with a variable range of manifestations. The fragile X syndrome may be helpful as a biologic model for studying the relationship between specific genetic factors and biological forms of psychopathology.

Psychopathology in fragile X syndrome

The fragile X syndrome is the most common known familial form of mental retardation. Young males commonly demonstrate hyperactivity and a short attention span, as well as physical abnormalities, some of which may lead to a diagnosis of Pervasive Developmental Disorder. Heterozygous females frequently demonstrate both a range of involvement with learning disabilities in math, and social anxiety. The more classical physical and behavioral features of this syndrome are reviewed.

Fragile X syndrome

Fragile X syndrome is one of the most intriguing genetic conditions now being studied. As the most common inherited form of mental retardation, it has an incidence of approximately 1 in 1000 male infants and boys. Because the cytogenetic diagnosis has only recently been available, many affected boys and female carriers have not yet been identified. This article reviews the characteristic, clinical features of fragile X syndrome and discusses treatment and intervention.

Do some patients with fragile X syndrome have precocious puberty?

We report on an 8 1/2-year-old white girl with fra (X) syndrome; she had mental deficiency, hyperactivity, speech disturbances, slightly prominent ears, mild joint laxity and 20% fra (X) expression. Additional findings include idiopathic precocious puberty and a right ovarian cyst. Ovarian cysts have been reported previously in heterozygous females, but to our knowledge idiopathic precocious puberty is a new finding in this syndrome. Whether precocious puberty is a coincidental finding in this patient or a previously unreported manifestation of the fra (X) syndrome is not clear.

New perspectives in autism, Part II: The differential diagnosis and neurobiology of autism

The clinical spectrum of autism spans a broad range of functions, but the core symptoms remain the same regardless of the intelligence of the child: the autistic type of social deficit that ranges from a lack of inclination to relate to extreme difficulty with the mechanics of social interactions, a global communication deficit that involves both verbal and nonverbal modes, and a severe cognitive deficit involving concept formation (abstraction) that is combined with an exceptional memory for factual information. These symptoms may vary dramatically in severity, but the basic deficits are identifiable regardless of IQ. Under-recognition of autism is a major problem at all IQs, but especially in patients with IQs above 50. No drugs have been found to significantly improve the core deficits in autism. Antipsychotics should be avoided except for short-term use. Antidepressants, anxiolytics, and anticonvulsants are important in the treatment of depression, affective modulation, situation-related stress, and seizures. Intensive social skills training is assuming a prominent role in behavior modification programs, and success with higher-functioning autistic children suggests that outcome can be improved by intensive training. The neurobiology of autism has also undergone dramatic changes. The psychogenic theories of etiology have been completely invalidated. Autism is now considered to be a neurological disorder resulting from an error in brain development. The precise location and nature of this deficit are still being actively debated and investigated. One theory emphasizes a dysfunction of the limbic system that results in an impairment in the acquisition of information. A second theory proposes a primary role for dysfunction of the cortical association network responsible for the processing of information.

Cognitive profiles of boys with the fragile X syndrome

Testing 20 boys with the fragile X (or Martin-Bell) syndrome with the Kaufman Assessment Battery for Children (K-ABC) showed a consistent pattern of strengths and weaknesses that may be useful in predicting a fragile X positive result from cytogenetic testing. This K-ABC pattern included 1) Sequential Scale score less than the Simultaneous Scale score; 2) Mental Processing Composite less than the Achievement Scale score; 3) Spatial Memory subtest score less than the Matrix Analogies subtest score; and 4) Arithmetic subtest score less than the mean of the Achievement subtest scores. A comparison group of 20 boys did not demonstrate such a pattern. Testing with the K-ABC should be considered for boys who present as learning disabled, hyperactive with attentional problems, or mildly retarded. Boys with three or four of the four features of the K-ABC fragile X pattern should be considered for medical evaluation and cytogenetic testing.