Fragile-X syndrome: variability of phenotypic expression

Predictors of cognitive, behavioural and academic difficulties in NF1

The impact of the Neurofibromatosis type 1 (NF1) on cognition have been subject to much clinical investigation, but environmental modifiers of disease expression have not yet been systematically investigated. The aim of this paper is to determine the role of demographic and environmental factors such as age, sex, socioeconomic status, parental NF1 status and neurological complications on the cognitive, behavioural and academic outcomes in NF1. Participants included 206 children aged 4-18 years seen within the Manchester clinical research NF1 service. Multiple linear regression models were used to study the effect of the hypothesized predictor variables on cognitive, behavioural and academic outcomes. Relative to population norms, 80% of the NF1 sample demonstrated significantly lower scores in at least one cognitive, behavioural or academic domains. Family history of NF1 and lower SES were independently associated with poorer cognitive, behavioural and academic outcomes. Neurological problems such as epilepsy and hydrocephalus were associated with lower IQ and academic skills. Cognitive and behavioural phenotypes emerge commonly via a complex interplay between genes and environmental factors, and this is true also of a monogenic condition such as NF1. Early interventions and remedial education may be targeted to risk groups such those with familial NF1, families with lower SES and those with associated neurological comorbidities.

Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders

There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.

Psychiatric and autistic comorbidity in fragile X syndrome across ages

Fragile X syndrome is caused by CGG trinucleotide repeat expansion within the fragile X mental retardation 1 gene, when repeat number exceeds 200. The typical psychiatric profile of fragile X syndrome patients includes cognitive and behavioral deficits, psychiatric comorbidity, and autistic characteristics. Specific psychiatric features have not yet been clarified, specifically in relationship to age and genetic characteristics. The objective of this study was to characterize psychiatric comorbidities in subjects with fragile X syndrome at different ages. Subjects with fragile X syndrome and their unaffected siblings were recruited and their parents filled out functional-behavioral and psychiatric comorbidities questionnaires. Adolescents with fragile X syndrome showed decreased prevalence of functional-behavioral deficits. Incidence and severity of most psychiatric comorbidities were lower in older subjects. Incidence of generalized anxiety disorder increased with age in the fragile X syndrome group. The typical profile of patients with fragile X syndrome changes with age. Unaffected siblings exhibit anxiety and motor tics.

Genetic reduction of group 1 metabotropic glutamate receptors alters select behaviors in a mouse model for fragile X syndrome

INTRODUCTION

Genetic heterogeneity likely contributes to variability in the symptoms among individuals with fragile X syndrome (FXS). Studies in the Fmr1 knockout (KO) mouse model for FXS suggest that excessive signaling through group I metabotropic glutamate receptors (Gp1 mGluRs), comprised of subtypes mGluR1 and mGluR5, may play a role. Hence, Gp1 mGluRs may act as modifiers of FXS. Currently no studies have addressed whether manipulation of mGluR1 activity may alter Fmr1 KO behavioral responses, and only a few have reported the effects of mGluR5 manipulation. Therefore, the goals for this study were to extend our understanding of the effects of modulating Gp1 mGluR activity on Fmr1 KO behavioral responses.

METHODS

The present study determined if genetically reducing mGluR1 or mGluR5 by 50% affects an extensive array of behaviors in the Fmr1 KO.

RESULTS

Reduction of mGluR1 moderately decreased Fmr1 KO activity. Reduction of mGluR5 caused an analgesic response in the Fmr1 KO and decreased active social behavior. Modulation of either mGluR1 or mGluR5 did not significantly alter audiogenic seizures, anxiety- and perseverative-related responses, sensorimotor gating, memory, or motor responses.

CONCLUSIONS

Genetic reduction of mGluR1 or mGluR5 modified a few select Fmr1 KO behaviors, although these modifications appeared to be subtle in nature and/or limited to select behaviors. This may indicate that 50% reduction of either mGluR1 or mGluR5 is insufficient to produce behavioral changes, and therefore, these receptors may not be dominant modifiers of a number of Fmr1 KO behavioral phenotypes.

Motor deficits on a ladder rung task in male and female adolescent and adult CGG knock-in mice

The fragile X premutation is a tandem CGG trinucleotide repeat expansion on the FMR1 gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse with CGG trinucleotide repeat lengths between 70 and 350 has been developed and used to model the histopathology and cognitive deficits reported in carriers of the fragile X premutation. Previous studies have shown that CGG KI mice show progressive deficits in processing spatial and temporal information. To characterize the motor deficits associated with the fragile X premutation, male and female CGG KI mice ranging from 2 to 16 months of age with trinucleotide repeats ranging from 72 to 240 CGG in length were tested for their ability to perform a skilled ladder rung walking test. The results demonstrate that both male and female CGG KI mice showed a greater number of foot slips as a function of increased CGG repeat length, independent of the age of the animal or general activity level.

Autism spectrum disorder in fragile X syndrome: a longitudinal evaluation

The present study extends our previous work on characterizing the autistic behavior profile of boys with fragile X syndrome (FXS) who meet Diagnostic and Statistical Manual for Mental Disorders, 4th Edition criteria for autism spectrum disorder (ASD) into a longitudinal evaluation of ASD in FXS (FXS + ASD). Specifically, we aimed to determine the stability of the diagnosis and profile of ASD in FXS over time. Through regression models, we also evaluated which autistic and social behaviors and skills were correlates of diagnosis and autistic behavior severity (i.e., Autism Diagnostic Interview-Revised total scores). Finally, we assessed the evolution of cognitive parameters in FXS + ASD. A population of 56 boys (30-88 months at baseline) with FXS was evaluated using measures of autistic, social, and cognitive behaviors and skills at three yearly evaluations. We found that the diagnosis of ASD in FXS was relatively stable over time. Further emphasizing this stability, we found a set of behaviors and skills, particularly those related to peer relationships and adaptive socialization, that differentiated FXS + ASD from the rest of the FXS cohort (FXS + None) and contributed to autistic severity at all time points. Nevertheless, the general improvement in autistic behavior observed in FXS + ASD coupled with the concurrent worsening in FXS + None resulted in less differentiation between the groups over time. Surprisingly, FXS + ASD IQ scores were stable while FXS + None non-verbal IQ scores declined. Our findings indicate that ASD is a distinctive subphenotype in FXS characterized by deficits in complex social interaction, with similarities to ASD in the general population.

[From a categorical diagnostic approach to a dimensional approach for mental disorders: interest of sex differences]

A strong prevalence of females or males is often found in mental disorders. Based on examples of anorexia (90% females) and autistic disorder (80 to 90% males), arguments that allow a better understanding of these different sex ratios are presented. The role of certain sociocultural factors in the onset of anorexia is developed. The predominance of males in autistic disorder has led to genetic and hormone-based biological hypotheses. However, it is also possible that the cultural representation of sex roles and its effects (expectation, different attitudes and behaviors depending on the child's gender) influence the development of social interaction and communication domains which are impaired in autistic disorder. Indeed, according to most studies, parents solicit and stimulate more social interaction and communication (eye contact specially during the first months of life, vocalizations then verbal language, emotional expression) in girls than in boys during the first three years of life, which corresponds to the period when autistic disorder appears. It is possible that because girls are more solicited than boys in social interaction and communication domains, during a sensitive (or critical) period of development, we may observe that girls show less autistic impairment in reciprocal social interaction and verbal or non-verbal communication, which are two of the three main domains of autistic disorder. It is also possible that impairments in social interaction and communication may be identified earlier for girls than for boys, which could lead to earlier therapeutic care for girls. Indeed, if parents have greater expectations for girls in social interaction and/or communication domains, they may worry more for their girl than for their boy with regard to developmental delay in these domains, and then may ask for professional advice earlier. This is what we have observed in our clinical practice and research, in which we conducted a follow-up in young girls showing autistic disorder aged two and half years old and who evolved positively; in contrast we have observed that parents bring their son for professional advice later, after kindergarten begins. Finally, a more complex, non-linear model is proposed in which biological genetic factors (such as sex-linked chromosomes) and/or hormonal factors (such as sex hormones) may play a role in differentiation of girls' and boys' behavior from birth. These different behaviors would induce differentiated expectations and attitudes in parents depending on the child's gender, which in turn would reinforce sex-related characteristic behaviors in the child. Thus, there may be a continuum in different behavioral domains (for example, boys would interact and communicate less than girls, and girls would express more their emotions), with mental disorders occurring at the extremes of this continuum (for example, autistic disorder for certain boys and anxiety disorder for certain girls). This hypothesis fits within an integrated psycho-biological approach that takes into account sex differences in mental disorders; it stems from a model in which a dimensional conception of mental disorders replaces a categorical nosographical one. New perspectives could be envisioned concerning the identification, follow-up and treatment of mental disorders (or sub-types of mental disorders), which are currently considered to belong to different nosographical categories, but which could overlap through shared common dimensions.

Language development and fragile X syndrome: profiles, syndrome-specificity, and within-syndrome differences

Fragile X syndrome (FXS) is the leading inherited cause of mental retardation. In this article, we review what is known about the language and related problems of individuals with FXS. In doing so, we focus on the syndrome-specific features of the language phenotype and on the organismic (i.e., genetic and individual neurocognitive and behavioral) and environmental factors associated with within-syndrome variation in the phenotype. We also briefly review those aspects of the behavioral phenotype of FXS that are relevant for understanding syndrome-specific features of, and within-syndrome variability in, language. The review includes summaries of research on the prelinguistic foundations for language development and on each of the major components of language (i.e., vocabulary, morphosyntax, and pragmatics). Throughout the review, we point out implications of existing research for intervention as well as directions for future research.

Autism spectrum disorder in fragile X syndrome: communication, social interaction, and specific behaviors

The present study extends our previous work on social behavior impairment in young males with fragile X syndrome (FraX). Specifically, we evaluated whether the autistic phenomenon in FraX is expressed as a range of behavioral impairments as in idiopathic autism (Aut). We also examined whether there are behaviors, identified as items of the Autism Diagnostic Interview-Revised (ADI-R), that in FraX predispose to or differentiate subjects with autism spectrum disorder (ASD) diagnosis. Finally, regression models were utilized to test the relative contribution of reduced communication and socialization skills to ADI-R scores and diagnoses. A cohort of 56 boys (3-8 years) with FraX was examined in terms of scores on measures of cognition (IQ was a co-variate in most analyses.), autistic behavior, problem/aberrant behavior, adaptive behavior, and language development. We found that, indeed, in terms of problem behavior and adaptive skills, there is a range of severity from FraX + Aut to FraX + PDD (Pervasive Developmental Disorder) to FraX + none. ADI-R items representing "Play" types of interaction appear to be "susceptibility" factors since they were abnormal across the FraX cohort. Integrated regression models demonstrated that items reflecting complex social interaction differentiated the FraX + ASD (Aut + PDD) subgroup from the rest of the FraX cohort, while abnormalities in basic verbal and non-verbal communication distinguished the most severely affected boys with FraX + Aut from the milder FraX + PDD cohort. Models incorporating language, adaptive communication, and adaptive socialization skills revealed that socialization was not only the main influence on scores but also a predictor of ASD diagnosis. Altogether, our findings demonstrate that the diagnosis of ASD in FraX reflects, to a large extent, an impairment in social interaction that is expressed with variable severity in young males with FraX.

The influence of environmental and genetic factors on behavior problems and autistic symptoms in boys and girls with fragile X syndrome

OBJECTIVE

Fragile X syndrome, caused by mutations in a single gene of the X chromosome (FMR1), is associated with neurobehavioral characteristics including social deficits with peers, social withdrawal, gaze aversion, inattention, hyperactivity, anxiety, depression, and autistic behavior. However, there is considerable variability in the behavioral and psychiatric problems among children with this condition. The purpose of this study was to measure genetic and environmental factors influencing behavior problems and autistic symptoms in children with fragile X syndrome.

DESIGN

We conducted an in-home evaluation of 120 children (80 boys and 40 girls) with the fragile X full mutation and their unaffected siblings, including measurements of the FMR1 protein (FMRP), quality of the home environment, maternal and paternal psychopathology, effectiveness of educational and therapeutic services, and child behavior problems.

RESULTS

Results of multiple regression analyses showed that for boys with fragile X, effectiveness of educational and therapeutic services and parental psychological problems predicted internalizing and externalizing types of problems, while the quality of the home environment predicted autistic behavior. For girls with fragile X, the results emphasized significant effects of FMRP on behavior, in particular social withdrawal and anxious/depressed behavior.

CONCLUSIONS

These findings are among the first to link FMRP expression to behavior. They also emphasize the significance of home- and school-based environmental variables in the neurobehavioral phenotype and help to lay the foundation for studies designed to identify specific interventions for reducing problem behavior in children with fragile X syndrome.

Future directions for neurobehavioral studies of environmental neurotoxicants

Three proposals for enriching neurobehavioral toxicology studies are discussed. First, while IQ has proven useful as a primary endpoint, such apical measures are limited: they obscure important individual differences, tend to reflect the product rather than the process of learning, sample a limited range of intelligent behaviors, and are insensitive to critical outcomes such as learning disabilities. In terms of societal disease burden, behavioral and psychiatric morbidities might be even more important than cognitive morbidities. Such endpoints warrant careful attention. Second, the models of child development can be enriched, increasing our ability both to control for confounding bias and to evaluate potential modification of neurotoxicant effects by contextual factors. While the use of the Home Observation for Measurement of the Environment (HOME scale) and other measures of family-level proximal factors was an important advance, recent sociological work demonstrates the importance of broader conceptualizations of the ecology of child development (e.g. neighborhood and community characteristics). Third, much effort has been expended in attempts to identify the behavioral signature associated with exposure to a particular neurotoxicant. Given the limited success in identifying behavioral phenotypes even for well-characterized genetic disorders (e.g. Fragile-X, Williams, Velocardiofacial syndromes), the prospects seem grim for identifying specific and relatively invariant patterns in the expression of neurotoxicant effects across diverse dosing regimens and biological and cultural settings. In part this results from the likely influence of complex, but largely unknown, patterns of effect modification on the expressions of toxicity. Efforts to define the nature of these contingencies might be more productive than continued efforts to identify behavioral phenotypes.

Autistic behavior, FMR1 protein, and developmental trajectories in young males with fragile X syndrome

In the context of a longitudinal study, we assessed the relationship between ratings of autistic behavior, FMR1 protein expression (FMRP), and the developmental trajectories of 55 young males with fragile X syndrome. Autistic behavior, as measured by the Childhood Autism Rating Scale, was not related to FMRP expression. However, autistic behavior was a significant predictor of both developmental status and developmental change. Boys with both autistic behavior and fragile X syndrome functioned at significantly lower levels of development and grew at significantly slower rates than those without autistic behavior. FMRP expression accounted for less variance in developmental level than did autistic behavior, and was not significantly related to slope (developmental change over time). No autistic behavior x FMRP interaction was found.

Autistic behavior in young boys with fragile X syndrome

A sample of 57 boys with fragile X syndrome (fraX) between the ages of 24 and 133 months was rated using the Childhood Autism Rating Scale (CARS) to assess the extent to which autism and autistic features were evident in a young population. Fourteen subjects (approximately 25% of the sample) scored above the cutoff for autism, suggesting a relatively high incidence of autistic behavior. All but 2 of these 14 were in the mildly or moderately autistic range, however, and only a few items received severe ratings, suggesting that severe autism is relatively rare in fraX, at least during the early years. The CARS resulted in a continuum of autistic ratings in the fraX population, but no particular items on the CARS contributed disproportionately to autism ratings. A visual comparison of ratings on an autistic, non-fraX sample revealed similar profiles of ratings, suggesting that differentiating fraX and autism on the basis of CARS ratings is not likely. Within the fraX group, chronological age and socioeconomic status did not correlate with CARS ratings, but severity of delay was strongly related, such that more severely delayed children scored higher (more autistic) on the CARS.

Autism: the point of view from fragile X studies

The relationship between the fragile X syndrome (FXS) and autism is reviewed. Shortly after the FXS was first described, it was noted that certain behaviors commonly found in afflicted individuals resemble certain features of autism. Research concerning a possible relationship between these conditions is summarized. The outcome of this research indicates that FXS is not a common cause of autism, although the number of individuals with FXS who meet diagnostic criteria for autism is higher than can be accounted for by chance. The major focus of this paper highlights that FXS is a well-defined neurogenetic disease that includes a cognitive behavioral phenotype, and has both a known biological cause and an increasing well-delineated pathogenesis. Autism is a behaviorally defined syndrome whose syndromic boundaries and biological causes are not known. These profound differences complicate comparisons and causal discussions. However, the behavioral neurogenetic information available about FXS suggests certain pathways for future research directed at elucidating the syndrome of autism.

The psychoeducational profile of boys with Klinefelter syndrome

Klinefelter syndrome (KS) affects about 1 in 900 males due to an extra X chromosome. Although there are no obvious physical features associated with childhood KS, many boys demonstrate a cognitive deficit in verbal processing. The first section of this article integrates the extant literature on intelligence and achievement outcomes in boys with KS. The second section presents our findings from a 20-year study involving one of the largest unselected cohorts of boys with KS. We followed 36 boys with KS and 33 sibling controls from 6 until 20 years of age. Boys with KS are shown to demonstrate a verbal cognitive deficit and significant underachievement in reading and spelling, as well as in arithmetic. These problems, which are evident from early school years, increase with age such that by late adolescence, boys with KS are four to five grade levels behind. In addition, we also found that they were most likely to have a generalized type of learning disability, with very few boys indicating a pure reading or pure arithmetic problem. They also showed deficits in written language skills and acquisition of knowledge-based subject material were also problematic. Despite significant underachievement and frequent grade failure, many boys with KS had completed high school, and a few were also pursuing postsecondary educations. The discussion section examines how their language-based disability affects comprehension and learning, leading to underachievement.

Facial emotion identification in males with fragile X syndrome

Fifteen postpubertal males with fragile X syndrome (FRA(X)) and 15 non-FRA(X) males matched on IQ and age were assessed for their ability to identify the facially expressed emotions of happiness, sadness, anger, fear, disgust, and surprise. Emotions of happiness and sadness were the easiest to identify for both groups of participants. Regardless of etiology, individuals with higher IQ scores performed better at this task than did individuals with lower IQ scores. Results were consistent with findings in females having the fragile X mutation. The current study supported the notion that FRA(X) individuals are sensitive to facial emotion cues presented by others. This finding is discussed in the context of autism and gaze aversion.

Evidence for a discrete behavioral phenotype in the oculocerebrorenal syndrome of Lowe

The oculocerebrorenal syndrome of Lowe (OCRL) is an X-linked disorder characterized by congenital cataracts, cognitive impairment, and renal tubular dysfunction. Although there is a wide range of intellectual function in affected individuals, it is often compromised by a high prevalence of maladaptive behaviors, including tantrums, stubborness, and stereotypy. Whether these behaviors simply reflect the multiple disabilities found in some developmentally impaired individuals with or without OCRL, or a specific genetically-determined behavioral phenotype of OCRL, is unknown. Controls were matched for sex, age, visual impairment, and adaptive functioning and compared with OCRL patients on three standardized measures of adaptive/maladaptive behaviors. Forty-three matched pairs of OCRL and control subjects were identified. Both groups were similar in communication, daily living, socialization, and motor skills, in socioeconomic status, and in measures of parental stress. Individuals with OCRL displayed significantly more severe maladaptive behaviors than control boys, as measured by the Vineland Adaptive Behavior Scales (VABS), with 41% of the difference between the two groups attributable to the diagnosis of OCRL. Twelve maladaptive behaviors measured on the VABS appeared more frequently in OCRL than in controls. Five of these 12 behaviors, i.e., temper tantrums, irritability, complex repetitive behaviors (stereotypy)/mannerisms, obsessions/unusual preoccupations, and negativism, were identified by discriminant function analysis to significantly distinguish between controls and OCRL individuals. The diagnosis of OCRL is associated with a behavioral phenotype consisting of temper tantrums, stereotypy, stubborness, and obsessions/unusual preoccupations. This phenotype cannot be attributed solely to the visual, motor, and intellectual disabilities characteristic of OCRL, and may represent a specific effect of the OCRL gene on the central nervous system.

Parents and collateral relatives of children with pervasive developmental disorders: a family history study

The objective of this study was to see whether, using the family history method, the risk for pervasive developmental disorder (PDD), cognitive impairments, and other psychiatric symptoms is greater in the parents and collateral relatives of probands with PDD compared to a control group. A semistructured family history interview was carried out with the parents of 52 probands with PDD and 33 parents of controls. Rates of cognitive impairments and psychiatric problems were not found more frequently in parents or relatives of PDD probands compared to relatives of controls, but four cases of PDD were reported among the extended families of the PDD probands. The relatives with PDD were related to the probands through the maternal line, possibly suggesting some form of maternal influence on inheritance or reduced penetrance in females with the PDD genotype.

Plasma androgens in autism

Plasma levels of testosterone and the adrenal androgen dehydroepiandrosterone sulfate (DHEA-S) were measured in male autistic subjects (31 prepubertal, 8 postpubertal), mentally retarded/cognitively impaired subjects (MR, 12 prepubertal), and normal control subjects (NC, 10 prepubertal, 11 postpubertal). Mean levels of plasma testosterone were similar in the postpubertal autistic (4.54 +/- 1.12 ng/ml) and postpubertal NC (5.02 +/- 1.87 ng/ml) groups. Plasma DHEA-S levels in postpubertal autistic (2170 +/- 1020 ng/ml) and postpubertal NC (1850 +/- 777 ng/ml) groups also were not significantly different. Similarly, no significant group differences were seen for testosterone or DHEA-S in the prepubertal autistic, MR, or NC individuals, although prepubertal MR individuals with cerebral palsy did have increased plasma DHEA-S levels compared to age-matched MR or NC individuals. Significant negative correlations were found between testosterone and whole blood serotonin (5-HT) levels in the combined (all subjects, all ages) groups and in the autistic group, suggesting that the effect of puberty on whole blood 5-HT may deserve further study. Data indicate that altered secretion of the androgens is not a common feature of autism. However, abnormalities of adrenal androgen secretion may be present in individuals with cerebral palsy.

Does IQ decline with age in fragile-X? A methodological critique

The recent claims for a decline in intelligence test performance in males and females with fragile-X (fra(X)) syndrome have implications both clinically and in evaluating the underlying neurological basis. This commentary identifies three key issues in evaluating evidence for a decline and in planning future, more co-ordinated efforts. These are (1) problems in combining data across different intelligence tests and/or different ages with potentially incompatible norms, task demands, and models of the structure of intelligence; (2) limitations in applying to low ability persons tests designed to discriminate best around the population average; and (3) specific cognitive deficits and behavioral problems in fra(X) individuals which may be confounded with the task demands of particular IQ tests at particular ages. While the decline in ability may be a real phenomenon rather than an artifact, recommendations are made about the psychometric requirements for a larger and more definitive collaborative study.

Folic acid in neurodevelopment and child psychiatry

1. Folic acid deficiency has been associated with diverse neuropsychiatric symptoms. 2. This paper discusses the impact of folate on brain development, maturation and function and reviews the role of folate in psychiatric disorders, particularly childhood disorders. 3. A brief case report examines the use of folate in the treatment of attentional problems in a child with fragile 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.

Fragile X (Martin-Bell) syndrome

Fragile X syndrome is a common condition resulting from a cytogenetic abnormality in the X chromosome. Mental retardation, characteristic facies, and large testes are some of the most important characteristics of the condition. The relatively high incidence of the syndrome--approximately one per thousand--the high incidence of cardiac anomalies in these individuals, the oral and facial features associated with the condition, and the paucity of reported cases in the dental literature make it particularly interesting to dentistry. Here we report the case of a 12-year-old male, including the cytogenetic and cephalometric analyses, presenting with some of the classic features and some features not commonly reported.

What is associated with the fragile X syndrome?

In addition to mental retardation (MR), fragile X[fra(X)] syndrome has been associated with a variety of other disorders. Despite earlier reports, it has been shown that MR fra(X) males are at no greater risk for autism than is any MR male. Therefore, studies in which fra(X) has been associated with behavioral, developmental, and psychopathological disabilities were examined to determine whether fra(X) individuals were at an increased risk for these dysfunctions as well. Psychiatric disorders among fra(X) individuals were found not to occur more frequently than in other individuals with cognitive deficits. It was also observed that hyperactivity and attention deficit disorder among MR fra(X) individuals do not occur more frequently than in other MR individuals. Pooled results from studies of cognitive profiles used to characterize fra(X) phenotypes also indicated that there are no consistent patterns in either males or females. Plausible explanations for a variable phenotype include allelic heterogeneity and pleitropy.

The psychoeducational characteristics of children with Turner syndrome

Turner syndrome (TS) is a condition that affects 1 in 2,500 females due to a loss of some X chromosome material. It is characterized by a number of common physical features, including short stature, sexual infantilism, and infertility, as well as by specific learning and behavior problems. This article compares abilities, achievement, behavior, and self-esteem in 67 children with TS and 27 nonaffected controls. Results indicate selective impairments in visuospatial and memory areas and significant underachievement in arithmetic, particularly numerical ability, mental calculation, geometry, and reasoning. Learning problems, a major concern for parents, were not being satisfactorily addressed at school. Poor social competence and increased behavior problems, particularly in the area of hyperactivity, were also noted. Although self-esteem was only marginally lower, issues related to poor peer relations were most problematic.

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.

Current developments in the understanding of mental retardation. Part II: Psychopathology

During recent years there has been greater recognition of the impressive degree of psychiatric disturbance that affects those with mental retardation. An increasing number of systematic studies are focusing on the prevalence, risk factors, and clinical characteristics of psychiatric disturbance within this population. In addition, traditional neuropsychiatric assessment and treatment approaches are being evaluated, and new approaches are being developed. Such efforts will undoubtedly improve the ability to effectively diagnose and treat mentally retarded individuals suffering from psychiatric disorders. This paper is the second of two reviews that explore several recent developments in biological, phenomenological, and psychopathological aspects of mental retardation.

Prevalence of fra(X) and other specific diagnoses in autistic individuals in a Danish county

In a Danish county (the island of Funen) cytogenetic screening for fragile X [fra(X)] of 32 autistic individuals aged 0-23 years showed a prevalence of 2/20 among boys and 0/12 among girls. In both cases additional fra(X) positive relatives were found. In 3 patients other chromosome aberrations were demonstrated and in one female Rett syndrome was diagnosed, initially suspected from observations of her behavior on videotapes. The presence of an underlying cause of autism in 6/32, of the patient group encourages an active search for a specific diagnosis among autistic males and females. Future screening of autistic individuals should include 1) fra(X) search also in females, 2) search for other chromosomal disorders, and 3) observation of behavior, in order to diagnose, i.e., Rett syndrome.

Developmental implications of changing trajectories of IQ in males with fragile X syndrome

This study examined the trajectories of cognitive development in boys under the age of 21 years with fragile X syndrome. By combining information from three centers, data from 66 boys were analyzed; only children who had been tested two or more times with the same psychometric instrument at one or more year intervals were included in this study. Results demonstrated that males with fragile X syndrome show a decline in IQ scores, with the most marked declines seen during the early pubertal period. All 22 children retested during the 11- to 15-year period showed IQ declines, suggesting a slowing of development associated with the onset of puberty. Before age 10 years, males with higher (as opposed to lower) pretest IQs were more likely to decline at subsequent testings. A single etiological factor may not be sufficient to account for the observed findings, as both changes in neurobiological- and task-related factors seem implicated in the slowing intellectual development of this population.

Autism is not associated with the fragile X syndrome

We provided a controlled test of the hypothesis that individuals with the Martin-Bell or Fragile X [fra(x)] syndrome are more autistic than mentally retarded control individuals. A sample of fra(x) individuals was obtained from the register of a clinical genetics unit and compared with mentally retarded control individuals selected from an assessment centre who were individually matched for age, sex, and IQ. A comparison of 45 pairs of fra(x) cases and control individuals on the DSM-III (R) criteria for autism and two standardized "instruments" for the assessment of autism (ABC and ADC) failed to find a higher prevalence of autism among fra(x) individuals. There was no statistically significant difference between fra(x) individuals and control individuals, and the mean differences on both the ABC and ADC scales were in the direction contrary to the hypothesis. An analysis of the study's statistical power suggested that it is unlikely the investigation failed to detect a large to medium difference between fra(x) individuals and control individuals in autistic behaviour. Subsidiary analyses of case-control differences showed that two autistic-like behaviours occurred at a higher rate among fra(x) individuals than other mentally retarded children, namely, gaze avoidance and hand flapping. These abnormalities may have misled clinicians into thinking that autism and fra(x) are associated.

Fragile X syndrome: genetic predisposition to psychopathology

Fragile X syndrome is a newly recognized X-linked disorder which has been associated with a high prevalence of psychiatric disturbance, particularly attention deficit disorder and autism. The present study involved the neuropsychiatric evaluation of 14 males with the disorder who were between the ages of 3 to 27 years. Pervasive hyperactivity, impulsivity, and attentional deficits were found among all of the subjects, while a significant degree of anxiety was manifested by more than half. Although the majority of subjects exhibited poor eye contact, atypical speech and language functioning, and stereotyped behavior, only one met DSM-III diagnostic criteria for a persistent pervasive developmental disorder. Gaze aversion, noted among half of the subjects, was attributed to underlying anxiety rather than to autistic social dysfunction because of the otherwise socially engaged and affectionate behavior exhibited by the subjects. Failure to make this distinction in the context of cognitive and linguistic impairments associated with fragile X syndrome may account for the high rates of autism reported by other investigators.