Prevalence of autism in a US metropolitan area

The Use of Two Language Tests to Identify Pragmatic Language Problems in Children With Autism Spectrum Disorders

Purpose: Pragmatic language disorders (PLDs) are difficult to diagnose in a cost-effective manner, and there are few assessment tools that yield quantitative data. This investigation was designed to determine whether two formal assessment tools would differentiate PLDs in children with autism spectrum disorders (ASDs) from controls matched on verbal IQ and language fundamentals.

Method: Thirty-four matched participants were given the Test of Pragmatic Language (TOPL; D. Phelps-Terasaki & T. Phelps-Gunn, 1992) and the Strong Narrative Assessment Procedure (SNAP; C. J. Strong, 1998).

Results: Participants with ASDs had significantly poorer scores than controls on the TOPL. On the SNAP, the children with ASDs performed similarly to controls on syntax, cohesion, story grammar, and completeness of episodes. The controls performed significantly better only on the ability to answer inferential questions.

Clinical Implications: The TOPL was effective in differentiating PLDs in children with ASDs when performance was compared to matched controls. The SNAP did not clearly differentiate language problems in these two groups. Research is needed to develop formal assessment tools that target the unique language disabilities of high-functioning individuals with ASDs.

Screening for autism in young children: The Modified Checklist for Autism in Toddlers (M-CHAT) and other measures

The literature on the importance of early identification and early intervention for children with developmental disabilities such as autism continues to grow. The increased prevalence of autistic spectrum disorders has fostered research efforts on the development and validation of autism-specific screening instruments for use with young children. There are currently several such autism-specific screening tools meant to be used with young children in various stages of development. Data from a few of these screening instruments have been published, and they include the Checklist for Autism in Toddlers (CHAT), Pervasive Developmental Disorders Screening Test (PDDST), Screening Tool for Autism in Two year olds (STAT), Checklist for Autism in Toddlers-23 (CHAT-23), and the Modified Checklist for Autism in Toddlers (M-CHAT). In this review, these five tools designed for use with children under three years old will be highlighted. In particular, the Modified Checklist for Autism in Toddlers (M-CHAT) will be discussed.

What's going on? The question of time trends in autism

Increases in the reported prevalence of autism and autistic spectrum disorders in recent years have fueled concern over possible environmental causes. The author reviews the available survey literature and finds evidence of large increases in prevalence in both the United States and the United Kingdom that cannot be explained by changes in diagnostic criteria or improvements in case ascertainment. Incomplete ascertainment of autism cases in young child populations is the largest source of predictable bias in prevalence surveys; however, this bias has, if anything, worked against the detection of an upward trend in recent surveys. Comparison of autism rates by year of birth for specific geographies provides the strongest basis for trend assessment. Such comparisons show large recent increases in rates of autism and autistic spectrum disorders in both the U.S. and the U.K. Reported rates of autism in the United States increased from < 3 per 10,000 children in the 1970s to > 30 per 10,000 children in the 1990s, a 10-fold increase. In the United Kingdom, autism rates rose from < 10 per 10,000 in the 1980s to roughly 30 per 10,000 in the 1990s. Reported rates for the full spectrum of autistic disorders rose from the 5 to 10 per 10,000 range to the 50 to 80 per 10,000 range in the two countries. A precautionary approach suggests that the rising incidence of autism should be a matter of urgent public concern.

Childhood autism spectrum disorder in the Barwon region: a community based study

OBJECTIVE

To establish a community database for children with autism spectrum disorder (ASD) to determine prevalence and identify subgroups based on key intellectual, clinical and family parameters.

METHODS

Data were collected for children previously diagnosed with an ASD in the Barwon region using parental interview and review of the child's paediatric and psychological records. Preschool diagnoses were typically made by specialist psychologists and school-age diagnoses made by a multidisciplinary team.

RESULTS

One hundred and seventy-seven children in the Barwon region were identified as having ASD (82% response rate). The prevalence of ASD was one per 255 children aged two to 17 years. The prevalence increased 10 fold over a 16-year period and this increase was relatively even across all levels of child intellectual functioning. Forty-two percent of children were intellectually disabled (IQ < 70) and performance IQ was significantly higher than verbal IQ but typical block design-comprehension subtest patterns were not common. Nine sibling pair families were identified, 24% were labelled as having attention deficit hyperactivity disorder (ADHD), 6% had epilepsy, and 18.3% were macrocephalic where data were available. Family difficulty was associated with the degree of obsessions/rituals, frequency and intensity of anger/aggression, and ADHD but overall was not associated with the child's intellectual status.

CONCLUSIONS

The relatively rapid increase in prevalence is consistent with overseas studies and suggests significant changes in diagnostic criteria, increasing community awareness and the need for support at all levels of intellectual functioning. Increased occurrence in siblings and relatives gives further evidence for a genetic cause.

Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism

BACKGROUND

Autism is a complex neurodevelopmental disorder that usually presents in early childhood and that is thought to be influenced by genetic and environmental factors. Although abnormal metabolism of methionine and homocysteine has been associated with other neurologic diseases, these pathways have not been evaluated in persons with autism.

OBJECTIVE

The purpose of this study was to evaluate plasma concentrations of metabolites in the methionine transmethylation and transsulfuration pathways in children diagnosed with autism.

DESIGN

Plasma concentrations of methionine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), adenosine, homocysteine, cystathionine, cysteine, and oxidized and reduced glutathione were measured in 20 children with autism and in 33 control children. On the basis of the abnormal metabolic profile, a targeted nutritional intervention trial with folinic acid, betaine, and methylcobalamin was initiated in a subset of the autistic children.

RESULTS

Relative to the control children, the children with autism had significantly lower baseline plasma concentrations of methionine, SAM, homocysteine, cystathionine, cysteine, and total glutathione and significantly higher concentrations of SAH, adenosine, and oxidized glutathione. This metabolic profile is consistent with impaired capacity for methylation (significantly lower ratio of SAM to SAH) and increased oxidative stress (significantly lower redox ratio of reduced glutathione to oxidized glutathione) in children with autism. The intervention trial was effective in normalizing the metabolic imbalance in the autistic children.

CONCLUSIONS

An increased vulnerability to oxidative stress and a decreased capacity for methylation may contribute to the development and clinical manifestation of autism.

Thimerosal and autism? A plausible hypothesis that should not be dismissed

The autism-mercury hypothesis first described by Bernard et al. has generated much interest and controversy. The Institute of Medicine (IOM) reviewed the connection between mercury-containing vaccines and neurodevelopmental disorders, including autism. They concluded that the hypothesis was biologically plausible but that there was insufficient evidence to accept or reject a causal connection and recommended a comprehensive research program. Without citing new experimental evidence, a number of observers have offered opinions on the subject, some of which reject the IOM's conclusions. In a recent review, Nelson and Bauman argue that a link between the preservative thimerosal, the source of the mercury in childhood vaccines, is improbable. In their defense of thimerosal, these authors take a narrow view of the original hypothesis, provide no new evidence, and rely on selective citations and flawed reasoning. We provide evidence here to refute the Nelson and Bauman critique and to defend the autism-mercury hypothesis.

Proteomic studies identified a single nucleotide polymorphism in glyoxalase I as autism susceptibility factor

Autism is a neurodevelopmental disability characterized by deficits in verbal communications, impairments in social interactions, and repetitive behaviors. Several studies have indicated strong involvement of multigenic components in the etiology of autism. Linkage analyses and candidate gene search approaches so far have not identified any reliable susceptibility genes. We are using a proteomic approach to identify protein abnormalities due to aberrant gene expression in autopsied autism brains. In four of eight autism brains, we have found an increase in polarity (more acidic) of glyoxalase I (Glo1) by two-dimensional gel electrophoresis. To identify the molecular change resulting in the shift of Glo1 polarity, we undertook sequencing of GLO1 gene. Direct sequencing of GLO1 gene/mRNA in these brains, has identified a single nucleotide polymorphism (SNP), C419A. The SNP causes an Ala111Glu change in the protein sequence. Population genetics of GLO1 C419A SNP studied in autism (71 samples) and normal and neurological controls (49 samples) showed significantly higher frequency for the A419 (allele frequency 0.6 in autism and 0.4 in controls, one-tailed Fisher's test P < 0.0079). Biochemical measurements have revealed a 38% decrease in Glo1 enzyme activity in autism brains (one-tailed t-test P < 0.026). Western blot analysis has also shown accumulation of advanced glycation end products (AGE's) in autism brains. These data suggest that homozygosity for A419 GLO1 resulting in Glu111 is a predisposing factor in the etiology of autism.

Early Indicators of Autism Spectrum Disorders in the Second Year of Life

Three groups of 18 children were selected for this study, one group with autism spectrum disorders (ASD), one group with developmental delays in which ASD was ruled out (DD), and one group with typical development (TD), from a pool of 3026 children who were screened with the Communication and Symbolic Behavior Scales Developmental Profile (CSBS DP, Wetherby & Prizant. 2002) Infant-Toddler Checklist under 24 months of age. The CSBS DP Behavior Sample was videotaped on selected children as a second-level evaluation during the second year of life. The Infant-Toddler Checklist had a sensitivity and specificity of 88.9% for this sample of children. Significant group differences were found on the Infant-Toddler Checklist and the Behavior Sample, however, these differences did not distinguish children with ASD and DD with high accuracy. The videotapes of the Behavior Sample were reanalyzed to identify red flags of ASD. Nine red flags differentiated children in the ASD group from both the DD and TD groups and four red flags differentiated children in the ASD Group from the TD group but not the DD group. These 13 red flags were found to discriminate the three groups with a correct classification rate of 94.4%.

Neurotoxic effects of postnatal thimerosal are mouse strain dependent

The developing brain is uniquely susceptible to the neurotoxic hazard posed by mercurials. Host differences in maturation, metabolism, nutrition, sex, and autoimmunity influence outcomes. How population-based variability affects the safety of the ethylmercury-containing vaccine preservative, thimerosal, is unknown. Reported increases in the prevalence of autism, a highly heritable neuropsychiatric condition, are intensifying public focus on environmental exposures such as thimerosal. Immune profiles and family history in autism are frequently consistent with autoimmunity. We hypothesized that autoimmune propensity influences outcomes in mice following thimerosal challenges that mimic routine childhood immunizations. Autoimmune disease-sensitive SJL/J mice showed growth delay; reduced locomotion; exaggerated response to novelty; and densely packed, hyperchromic hippocampal neurons with altered glutamate receptors and transporters. Strains resistant to autoimmunity, C57BL/6J and BALB/cJ, were not susceptible. These findings implicate genetic influences and provide a model for investigating thimerosal-related neurotoxicity.

Autism spectrum disorder: screening, diagnosis, and medical evaluation

Autism spectrum disorder (ASD) are a group of behaviorally defined neurodevelopmental disabilities with core deficits in socialization, communication, and behavior, although the presentation can be extremely variable. This article describes the core deficits in ASD, as well as the differential diagnosis and the more commonly associated comorbid disorders. The importance of early diagnosis is emphasized, and screening and assessment tools are reviewed. Finally, the role of the pediatric neurologist is discussed with regard to specific components of the evaluation, including history, physical examination, and ancillary testing.

Autism associated with conditions characterized by developmental errors in early embryogenesis: a mini review

Autism is a complex developmental disorder without an established single etiology but with significant contributions from genetic studies, functional research, and neuropsychiatric and neuroradiologic investigations. The purpose of this paper is to review the findings in five studies involving individuals manifesting the characteristic findings of autism spectrum disorder associated with malformations and dysfunctions known to result from early embryogenic defects. These investigations include two associated with teratogens (thalidomide embryopathy, Mobius sequence with misoprostol) and three (most Mobius sequence cases, CHARGE association, Goldenhar syndrome) with no known etiology. These studies suggest that early embryonic development errors often involving cranial nerve palsies, internal and external ear malformations, ophthalmologic anomalies, and a variety of systemic malformations may be associated with autism spectrum disorders statistically more frequently than expected in a normal population. Although the exact time of developmental insult for each condition cannot be identified, the evidence is that it may occur as early as week 4 to 6+ of embryogenesis.

Public health monitoring of developmental disabilities with a focus on the autism spectrum disorders

Developmental disabilities (DDs) are conditions characterized by physical, cognitive, psychological, sensory, adaptive, and/or communication impairments manifested during development. Approximately 17% of individuals in the United States 18 years and younger have a DD, and for most children the cause of their condition is unknown. Of particular interest are the autism spectrum disorders (ASDs), characterized by unusual social, communication, and behavioral development. Previously autism was thought to be a rare condition, but the number of children receiving services for an ASD has increased dramatically in the last decade. Concerns about increases in DDs, particularly ASDs, their causes, and the high costs of intervention have highlighted the need for systematic public health monitoring. Service provider data, such as annual reporting of special education services or of state DD programs, do not provide a complete estimate of the rates for DDs, including ASDs. Unlike genetic metabolic disorders or congenital hearing loss (HL) for which newborn screening programs can provide accurate prevalence rates, there are currently no genetic or biologic markers for the ASDs to enable consistent and early identification of affected children. Centers for Disease Control and Prevention's (CDC) Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) is a model for population monitoring of ASDs/DDs that has been implemented in other states. This article discusses the role of ASD/DD tracking in public health, as well as the challenges of ASD/DD tracking, including case definition and identification, associated conditions, linkages, and data access.

Seizures and epilepsy among children with language regression and autistic spectrum disorders

Clinical and subclinical seizures occur frequently among children with autistic spectrum disorders. Electrographic status epilepticus in sleep, or continuous spike-wave in slow-wave sleep, is a typical feature of acquired epileptic aphasia and Landau-Kleffner syndrome. Seizures and epilepsy are more common among children with autistic spectrum disorder who experience language regression, especially those who experience language regression after the age of 2 years. Although the seizures associated with Landau-Kleffner syndrome and with acquired epileptic aphasia can be easily treated, improvement in language function often does not follow successful treatment of seizures. There are no published randomized clinical trials of treatments for Landau-Kleffner syndrome or for autistic language regression. Broad-spectrum antiepileptic drugs not associated with cognitive slowing are probably the treatment of choice for epilepsy among children with autistic spectrum disorder. Large multisite trials are needed to determine treatment efficacy among children with Landau-Kleffner syndrome and acquired epileptic aphasia and to establish whether there is a cause-effect relationship between electrographic status epilepticus in sleep or continuous spike-wave in slow-wave sleep and autistic language regression.

Neurodevelopment and endocrine disruption

In this article I explore the possibility that contaminants contribute to the increasing prevalence of attention deficit hyperactivity disorder, autism, and associated neurodevelopmental and behavioral problems in developed countries. I discuss the exquisite sensitivity of the embryo and fetus to thyroid disturbance and provide evidence of human in utero exposure to contaminants that can interfere with the thyroid. Because it may never be possible to link prenatal exposure to a specific chemical with neurodevelopmental damage in humans, I also present alternate models where associations have been made between exposure to specific chemicals or chemical classes and developmental difficulties in laboratory animals, wildlife, and humans.

Examination of NRCAM, LRRN3, KIAA0716, and LAMB1 as autism candidate genes

BACKGROUND

A substantial body of research supports a genetic involvement in autism. Furthermore, results from various genomic screens implicate a region on chromosome 7q31 as harboring an autism susceptibility variant. We previously narrowed this 34 cM region to a 3 cM critical region (located between D7S496 and D7S2418) using the Collaborative Linkage Study of Autism (CLSA) chromosome 7 linked families. This interval encompasses about 4.5 Mb of genomic DNA and encodes over fifty known and predicted genes. Four candidate genes (NRCAM, LRRN3, KIAA0716, and LAMB1) in this region were chosen for examination based on their proximity to the marker most consistently cosegregating with autism in these families (D7S1817), their tissue expression patterns, and likely biological relevance to autism.

METHODS

Thirty-six intronic and exonic single nucleotide polymorphisms (SNPs) and one microsatellite marker within and around these four candidate genes were genotyped in 30 chromosome 7q31 linked families. Multiple SNPs were used to provide as complete coverage as possible since linkage disequilibrium can vary dramatically across even very short distances within a gene. Analyses of these data used the Pedigree Disequilibrium Test for single markers and a multilocus likelihood ratio test.

RESULTS

As expected, linkage disequilibrium occurred within each of these genes but we did not observe significant LD across genes. None of the polymorphisms in NRCAM, LRRN3, or KIAA0716 gave p < 0.05 suggesting that none of these genes is associated with autism susceptibility in this subset of chromosome 7-linked families. However, with LAMB1, the allelic association analysis revealed suggestive evidence for a positive association, including one individual SNP (p = 0.02) and three separate two-SNP haplotypes across the gene (p = 0.007, 0.012, and 0.012).

CONCLUSIONS

NRCAM, LRRN3, KIAA0716 are unlikely to be involved in autism. There is some evidence that variation in or near the LAMB1 gene may be involved in autism.

The genetics of autism

Autism is a complex, behaviorally defined, static disorder of the immature brain that is of great concern to the practicing pediatrician because of an astonishing 556% reported increase in pediatric prevalence between 1991 and 1997, to a prevalence higher than that of spina bifida, cancer, or Down syndrome. This jump is probably attributable to heightened awareness and changing diagnostic criteria rather than to new environmental influences. Autism is not a disease but a syndrome with multiple nongenetic and genetic causes. By autism (the autistic spectrum disorders [ASDs]), we mean the wide spectrum of developmental disorders characterized by impairments in 3 behavioral domains: 1) social interaction; 2) language, communication, and imaginative play; and 3) range of interests and activities. Autism corresponds in this article to pervasive developmental disorder (PDD) of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition and International Classification of Diseases, Tenth Revision. Except for Rett syndrome--attributable in most affected individuals to mutations of the methyl-CpG-binding protein 2 (MeCP2) gene--the other PDD subtypes (autistic disorder, Asperger disorder, disintegrative disorder, and PDD Not Otherwise Specified [PDD-NOS]) are not linked to any particular genetic or nongenetic cause. Review of 2 major textbooks on autism and of papers published between 1961 and 2003 yields convincing evidence for multiple interacting genetic factors as the main causative determinants of autism. Epidemiologic studies indicate that environmental factors such as toxic exposures, teratogens, perinatal insults, and prenatal infections such as rubella and cytomegalovirus account for few cases. These studies fail to confirm that immunizations with the measles-mumps-rubella vaccine are responsible for the surge in autism. Epilepsy, the medical condition most highly associated with autism, has equally complex genetic/nongenetic (but mostly unknown) causes. Autism is frequent in tuberous sclerosis complex and fragile X syndrome, but these 2 disorders account for but a small minority of cases. Currently, diagnosable medical conditions, cytogenetic abnormalities, and single-gene defects (eg, tuberous sclerosis complex, fragile X syndrome, and other rare diseases) together account for <10% of cases. There is convincing evidence that "idiopathic" autism is a heritable disorder. Epidemiologic studies report an ASD prevalence of approximately 3 to 6/1000, with a male to female ratio of 3:1. This skewed ratio remains unexplained: despite the contribution of a few well characterized X-linked disorders, male-to-male transmission in a number of families rules out X-linkage as the prevailing mode of inheritance. The recurrence rate in siblings of affected children is approximately 2% to 8%, much higher than the prevalence rate in the general population but much lower than in single-gene diseases. Twin studies reported 60% concordance for classic autism in monozygotic (MZ) twins versus 0 in dizygotic (DZ) twins, the higher MZ concordance attesting to genetic inheritance as the predominant causative agent. Reevaluation for a broader autistic phenotype that included communication and social disorders increased concordance remarkably from 60% to 92% in MZ twins and from 0% to 10% in DZ pairs. This suggests that interactions between multiple genes cause "idiopathic" autism but that epigenetic factors and exposure to environmental modifiers may contribute to variable expression of autism-related traits. The identity and number of genes involved remain unknown. The wide phenotypic variability of the ASDs likely reflects the interaction of multiple genes within an individual's genome and the existence of distinct genes and gene combinations among those affected. There are 3 main approaches to identifying genetic loci, chromosomal regions likely to contain relevant genes: 1) whole genome screens, searching for linkage of autism to shared genetic markers in populations of multiplex families (families with >1 affected family member; 2) cytogenetic studies that may guide molecular studies by pointing to relevant inherited or de novo chromosomal abnormalities in affected individuals and their families; and 3) evaluation of candidate genes known to affect brain development in these significantly linked regions or, alternatively, linkage of candidate genes selected a priori because of their presumptive contribution to the pathogenesis of autism. Data from whole-genome screens in multiplex families suggest interactions of at least 10 genes in the causation of autism. Thus far, a putative speech and language region at 7q31-q33 seems most strongly linked to autism, with linkages to multiple other loci under investigation. Cytogenetic abnormalities at the 15q11-q13 locus are fairly frequent in people with autism, and a "chromosome 15 phenotype" was described in individuals with chromosome 15 duplications. Among other candidate genes are the FOXP2, RAY1/ST7, IMMP2L, and RELN genes at 7q22-q33 and the GABA(A) receptor subunit and UBE3A genes on chromosome 15q11-q13. Variant alleles of the serotonin transporter gene (5-HTT) on 17q11-q12 are more frequent in individuals with autism than in nonautistic populations. In addition, animal models and linkage data from genome screens implicate the oxytocin receptor at 3p25-p26. Most pediatricians will have 1 or more children with this disorder in their practices. They must diagnose ASD expeditiously because early intervention increases its effectiveness. Children with dysmorphic features, congenital anomalies, mental retardation, or family members with developmental disorders are those most likely to benefit from extensive medical testing and genetic consultation. The yield of testing is much less in high-functioning children with a normal appearance and IQ and moderate social and language impairments. Genetic counseling justifies testing, but until autism genes are identified and their functions are understood, prenatal diagnosis will exist only for the rare cases ascribable to single-gene defects or overt chromosomal abnormalities. Parents who wish to have more children must be told of their increased statistical risk. It is crucial for pediatricians to try to involve families with multiple affected members in formal research projects, as family studies are key to unraveling the causes and pathogenesis of autism. Parents need to understand that they and their affected children are the only available sources for identifying and studying the elusive genes responsible for autism. Future clinically useful insights and potential medications depend on identifying these genes and elucidating the influences of their products on brain development and physiology.

The developmental, dimensional and diagnostic interview (3di): a novel computerized assessment for autism spectrum disorders

OBJECTIVE

Autism is a diagnostic spectrum of variable severity, with significant comorbidity. No existing standardized interview measures autistic features dimensionally. The authors aimed to develop a parental autism interview that could be administered to unselected clinical and general population samples that measures both symptom intensity and comorbidity across the full range of the autistic spectrum.

METHOD

A computerized procedure was devised for administration by trained interviewers that generates symptom and diagnostic profiles for both autism and non-autistic conditions. Test-retest reliability and interrater reliability were assessed in unselected clinical (n = 50) and nonclinical (n = 30) populations. Concurrent validity (n = 120), discriminant validity (n = 120), and criterion validity (n = 29) were evaluated in autistic spectrum and non-autistic patients.

RESULTS

Test-retest and interrater reliabilities were excellent (most intraclass correlation coefficients > 0.9). Concurrent validity (agreement with independent clinician formulation) was very good (mean kappa = 0.74). Criterion validity, a comparison with the Autism Diagnostic Interview, was excellent. Discrimination between autistic spectrum versus non-autistic subjects was almost perfect (sensitivity 1.0; specificity > 0.97).

CONCLUSIONS

The Developmental, Dimensional and Diagnostic Interview (3di) provides an efficient and accurate means of assessing, in dimensional terms, the presence of autistic symptoms in both clinical and normal populations. It offers novel opportunities for those engaged in research and clinical practice.

Activation of methionine synthase by insulin-like growth factor-1 and dopamine: a target for neurodevelopmental toxins and thimerosal

Methylation events play a critical role in the ability of growth factors to promote normal development. Neurodevelopmental toxins, such as ethanol and heavy metals, interrupt growth factor signaling, raising the possibility that they might exert adverse effects on methylation. We found that insulin-like growth factor-1 (IGF-1)- and dopamine-stimulated methionine synthase (MS) activity and folate-dependent methylation of phospholipids in SH-SY5Y human neuroblastoma cells, via a PI3-kinase- and MAP-kinase-dependent mechanism. The stimulation of this pathway increased DNA methylation, while its inhibition increased methylation-sensitive gene expression. Ethanol potently interfered with IGF-1 activation of MS and blocked its effect on DNA methylation, whereas it did not inhibit the effects of dopamine. Metal ions potently affected IGF-1 and dopamine-stimulated MS activity, as well as folate-dependent phospholipid methylation: Cu(2+) promoted enzyme activity and methylation, while Cu(+), Pb(2+), Hg(2+) and Al(3+) were inhibitory. The ethylmercury-containing preservative thimerosal inhibited both IGF-1- and dopamine-stimulated methylation with an IC(50) of 1 nM and eliminated MS activity. Our findings outline a novel growth factor signaling pathway that regulates MS activity and thereby modulates methylation reactions, including DNA methylation. The potent inhibition of this pathway by ethanol, lead, mercury, aluminum and thimerosal suggests that it may be an important target of neurodevelopmental toxins.

Autism: a target of pharmacotherapies?

Autism is reaching epidemic proportions. The diagnosis can be made as early as 2 years of age, and autistic patients are expected to have a normal life span. Thus, in terms of the number of 'patient years', autism spectrum disorder (ASD) represents a market that is as large as that of the biggest neurological indication, Alzheimer's disease. However, despite the clear unmet medical need no effective treatment is yet available. This could be because the biology of ASD is not clearly understood and thus proper drug treatment has not been possible. However, significant advances are being made toward understanding the mechanisms of the disease. Here, we review the most recent preclinical advances in the hope that they will lead to a breakthrough in the near future.

Validation of the diagnosis of autism in general practitioner records

Background

We report on the validity of the computerized diagnoses of autism in a large case-control study investigating the possible association between autism and the measles, mumps and rubella vaccine in the UK using the General Practitioner Research Database (GPRD). We examined anonymized copies of all relevant available clinical reports, including general practitioners' (GP) notes, consultant, speech therapy and educational psychologists reports, on 318 subjects born between 1973 and 1997 with a diagnosis of autism or a related disorder recorded in their electronic general practice record.

Methods

Data were abstracted to a case validation form allowing for the identification of developmental symptoms relevant to the diagnosis of pervasive developmental disorders (PDDs). Information on other background clinical and familial features was also abstracted. A subset of 50 notes was coded independently by 2 raters to derive reliability estimates for key clinical characteristics.

Results

For 294 subjects (92.5%) the diagnosis of PDD was confirmed after review of the records. Of these, 180 subjects (61.2%) fulfilled criteria for autistic disorder. The mean age at first recording of a PDD diagnosis in the GPRD database was 6.3 years (SD = 4.6). Consistent with previous estimates, the proportion of subjects experiencing regression in the course of their development was 19%. Inter-rater reliability for the presence of a PDD diagnosis was good (kappa = .73), and agreement on clinical features such as regression, age of parental recognition of first symptoms, language delay and presence of epilepsy was also good (kappas ranging from .56 to 1.0).

Conclusions

This study provides evidence that the positive predictive value of a diagnosis of autism recorded in the GPRD is high.

No association between the APOE gene and autism

Autism is a neurodevelopmental disorder characterized by stereotypic and repetitive behavior and interests, together with social and communicative deficiencies. The results of several genomic screens suggest the presence of an autism susceptibility locus on chromosome 19p13.2-q13.4. The apolipoprotein E (APOE) gene on chromosome 19 encodes for a protein, apoE, whose different isoforms (E2, E3, E4) influence neuronal growth. APOE participates in lipid transport and metabolism, repair, growth, and maintenance of axons and myelin during neuronal development. The APOE protein competes with the Reelin protein for VLDL/APOER2 receptor binding. Several studies have reported evidence for an association between autism and the Reelin gene. Based on these data we tested for association between APOE and autism using family-based association methods in a data set of 322 autism families. Three promoter, one intronic, and one 3' UTR single nucleotide polymorphisms (SNPs) in the APOE gene (-491a/t, -427c/t, -219g/t, 113c/g, and 5361c/t) as well as the APOE functional polymorphism (E2, E3, E4) were examined and failed to reveal significant evidence that autism is associated with APOE.

Age at first measles-mumps-rubella vaccination in children with autism and school-matched control subjects: a population-based study in metropolitan atlanta

OBJECTIVE

To compare ages at first measles-mumps-rubella (MMR) vaccination between children with autism and children who did not have autism in the total population and in selected subgroups, including children with regression in development.

METHODS

A case-control study was conducted in metropolitan Atlanta. Case children (N = 624) were identified from multiple sources and matched to control children (N = 1824) on age, gender, and school. Vaccination data were abstracted from immunization forms required for school entry. Records of children who were born in Georgia were linked to Georgia birth certificates for information on maternal and birth factors. Conditional logistic regression was used to estimate odds ratios (ORs).

RESULTS

The overall distribution of ages at MMR vaccination among children with autism was similar to that of matched control children; most case (70.5%) and control children (67.5%) were vaccinated between 12 and 17 months of age. Similar proportions of case and control children had been vaccinated before 18 or before 24 months. No significant associations for either of these age cutoffs were found for specific case subgroups, including those with evidence of developmental regression. More case (93.4%) than control children (90.6%) were vaccinated before 36 months (OR: 1.49; 95% confidence interval: 1.04-2.14 in the total sample; OR: 1.23; 95% confidence interval: 0.64-2.36 in the birth certificate sample). This association was strongest in the 3- to 5-year age group.

CONCLUSIONS

Similar proportions of case and control children were vaccinated by the recommended age or shortly after (ie, before 18 months) and before the age by which atypical development is usually recognized in children with autism (ie, 24 months). Vaccination before 36 months was more common among case children than control children, especially among children 3 to 5 years of age, likely reflecting immunization requirements for enrollment in early intervention programs.

MMR Vaccination and Autism

It has been suggested that vaccination with the measles-mumps-rubella (MMR) vaccine causes autism. The wide-scale use of the MMR vaccine has been reported to coincide with the apparent increase in the incidence of autism. Case reports have described children who developed signs of both developmental regression and gastrointestinal symptoms shortly after MMR vaccination.A review of the literature revealed no convincing scientific evidence to support a causal relationship between the use of MMR vaccines and autism. No primate models exist to support the hypothesis. The biological plausibility remains questionable and there is a sound body of epidemiological evidence to refute the hypothesis. The hypothesis has been subjected to critical evaluation in many different ways, using techniques from molecular biology to population-based epidemiology, and with a vast number of independent researchers involved, none of which has been able to corroborate the hypothesis.

Examination of candidate genes in language disorder: A model of genetic association for treatment studies

The purpose of this review is to provide a model for studying genetic association of response to intervention in child language disorders. In addition to a theoretical overview and review of different approaches to studying candidate genes, a specific methodology for completing this type of analysis is presented. The goal of the analysis is to provide detail beyond simple broad phenotyping for affected and nonaffected individuals and to take advantage of data yielded from concise behavioral phenotyping often available in treatment studies.

The Neural Basis of Hyperlexic Reading

Children with autism spectrum disorders in very rare cases display surprisingly advanced "hyperlexic" reading skills. Using functional magnetic resonance imaging (fMRI), we studied the neural basis of this precocious reading ability in a 9-year-old hyperlexic boy who reads 6 years in advance of his age. During covert reading, he demonstrated greater activity in the left inferior frontal and superior temporal cortices than both chronological age- and reading age-matched controls. Activity in the right inferior temporal sulcus was greater when compared to reading age-matched controls. These findings suggest that precocious reading is brought about by simultaneously drawing on both left hemisphere phonological and right hemisphere visual systems, reconciling the two prevailing, but seemingly contradictory, single hemisphere theories of hyperlexia. Hyperlexic reading is therefore associated with hyperactivation of the left superior temporal cortex, much in the same way as developmental dyslexia is associated with hypoactivation of this area.

Epidemiology and Possible Causes of Autism

OBJECTIVES

To review the recent literature on possible causes of the increase in frequency of diagnosed autism reported from three countries, and to compare the medical diagnoses and drug therapy from a new series of autistic boys and their mothers with that of comparable nonautistic boys and their mothers.

DESIGN

Case-control evaluation.

PARTICIPANTS

Members of over 250 general practices in the United Kingdom.

MEASUREMENTS AND MAIN RESULTS

Frequency of exposure to drugs and presence of preexisting clinical illnesses in autistic children and their mothers were compared with nonautistic children and their mothers over time. According to published studies, the incidence of boys diagnosed with autism rose dramatically in the 1990s. Numerous published studies have concluded that the measles-mumps-rubella vaccine is not responsible for the large rise in diagnosed autism. In our study, boys diagnosed with autism had medical and drug histories, such as vaccines, before diagnosis, that were closely similar to those of nonautistic boys, except that developmental and sensory disorders were far more common in autistic boys. No material differences during pregnancy were found between the mothers of autistic boys and those of nonautistic boys in relation to illness or drug therapy. In the early 1990s, boys with diagnosed developmental disorders were infrequently diagnosed with autism. In the later 1990s, such boys more often were diagnosed with autism.

CONCLUSION

A major cause of the recent large increase in the number of boys diagnosed with autism probably is due to changing diagnostic practices.

Increased prevalence of familial autoimmunity in probands with pervasive developmental disorders

OBJECTIVES

Increased prevalence of familial autoimmune disease is a common finding among probands with various autoimmune disorders. Autistic disorder (autism) is a highly genetic disorder with known immune and immunogenetic abnormalities. Previous research has found an increased frequency of autoimmune disorders in families with autistic probands. We further investigated this association by determining the frequency of autoimmune disorders in families that have probands with pervasive developmental disorders (PDDs), including autism, compared with 2 control groups.

METHODS

Three well-defined study groups, including 1) families that have a child with a PDD, 2) families that have a child with an autoimmune disorder, and 3) families with a healthy control child, constituted the sample. A questionnaire inquiring about which first- and second-degree family members had received a diagnosis of having specific autoimmune disorders was completed by 101 families in each group.

RESULTS

The frequency of autoimmune disorders was significantly higher in families of the PDD probands compared with families of both the autoimmune and healthy control probands. Autoimmunity was highest among the parents of PDD probands compared with parents of the healthy control subjects. Hypothyroidism/Hashimoto's thyroiditis and rheumatic fever were significantly more common in families with PDD probands than in the healthy control families.

CONCLUSIONS

Autoimmunity was increased significantly in families with PDD compared with those of healthy and autoimmune control subjects. These preliminary findings warrant additional investigation into immune and autoimmune mechanisms in autism.

Bioinformatic analysis of autism positional candidate genes using biological databases and computational gene network prediction

Common genetic disorders are believed to arise from the combined effects of multiple inherited genetic variants acting in concert with environmental factors, such that any given DNA sequence variant may have only a marginal effect on disease outcome. As a consequence, the correlation between disease status and any given DNA marker allele in a genomewide linkage study tends to be relatively weak and the implicated regions typically encompass hundreds of positional candidate genes. Therefore, new strategies are needed to parse relatively large sets of 'positional' candidate genes in search of actual disease-related gene variants. Here we use biological databases to identify 383 positional candidate genes predicted by genomewide genetic linkage analysis of a large set of families, each with two or more members diagnosed with autism, or autism spectrum disorder (ASD). Next, we seek to identify a subset of biologically meaningful, high priority candidates. The strategy is to select autism candidate genes based on prior genetic evidence from the allelic association literature to query the known transcripts within the 1-LOD (logarithm of the odds) support interval for each region. We use recently developed bioinformatic programs that automatically search the biological literature to predict pathways of interacting genes (PATHWAYASSIST and GENEWAYS). To identify gene regulatory networks, we search for coexpression between candidate genes and positional candidates. The studies are intended both to inform studies of autism, and to illustrate and explore the increasing potential of bioinformatic approaches as a compliment to linkage analysis.

Use of complementary and alternative treatments for children with autistic spectrum disorders is increasing

Interventions considered to be CAM are in constant flux. New treatments emerge, older treatments become less popular, and the cycle recurs. Data supporting new treatments should be scrutinized for scientific study design, clinical safety, and scientific validity. Many families approach the clinician armed with brochures, handouts, and printouts from Web sites that are dedicated to the care and support of parents and children with ASD. A recent web search using "autism and detoxification" resulted in almost 8,000 sites. The Defeat Autism Now! (DAN!) Project arose in 1995 from collaboration of members of the Autism Research Institute. The DAN! Project advocates a specific and extensive protocol for diagnosis and treatment and can be viewed at http://www.autism.com/ari/#dan. The scientific validation and support for many interventions is incomplete and disparate from the recommendation in the American Academy of Pediatrics Policy Statement. Families should be encouraged to discuss all proposed investigations or treatments they wish to try with their primary care provider so the practitioner can serve as the medical home (Sidebar, page 688). The clinician should communicate and collaborate with the family and educational professionals to encourage objective identification of what works. With increasing access to health information and societal pressure for families to actively participate in their health management, continued growth of interest in CAM can be anticipated. Clinicians must remember that parents may have different beliefs regarding the effectiveness of treatment and different tolerance for treatment risks. Practitioners must keep avenues of communication open, remain open-minded, and not assume a "don't ask, don't tell" posture in the context of providing a medical home to the increasing number of children diagnosed with autism.

Epidemiology and etiology of autistic spectrum disorders difficult to determine

The epidemiology of the autistic spectrum disorders is changing. A clear increase in prevalence has been noted during the past 2 decades. What is less clear is the cause for this increase. Multiple factors appear to be responsible. The preponderance of evidence suggests most of the rise in incidence and prevalence is related to changes in diagnostic criteria and greater awareness on the part of both professionals and parents. Proposed theories of causation, which also seek to explain the increase in prevalence, have not been substantiated. Further research is needed to better determine the incidence and prevalence of these disorders and their etiologic factors.

A genomewide screen of 345 families for autism-susceptibility loci

We previously reported a genomewide scan to identify autism-susceptibility loci in 110 multiplex families, showing suggestive evidence (P <.01) for linkage to autism-spectrum disorders (ASD) on chromosomes 5, 8, 16, 19, and X and showing nominal evidence (P <.05) on several additional chromosomes (2, 3, 4, 10, 11, 12, 15, 18, and 20). In this follow-up analysis we have increased the sample size threefold, while holding the study design constant, so that we now report 345 multiplex families, each with at least two siblings affected with autism or ASD phenotype. Along with 235 new multiplex families, 73 new microsatellite markers were also added in 10 regions, thereby increasing the marker density at these strategic locations from 10 cM to approximately 2 cM and bringing the total number of markers to 408 over the entire genome. Multipoint maximum LOD scores (MLS) obtained from affected-sib-pair analysis of all 345 families yielded suggestive evidence for linkage on chromosomes 17, 5, 11, 4, and 8 (listed in order by MLS) (P <.01). The most significant findings were an MLS of 2.83 (P =.00029) on chromosome 17q, near the serotonin transporter (5-hydroxytryptamine transporter [5-HTT]), and an MLS of 2.54 (P =.00059) on 5p. The present follow-up genome scan, which used a consistent research design across studies and examined the largest ASD sample collection reported to date, gave either equivalent or marginally increased evidence for linkage at several chromosomal regions implicated in our previous scan but eliminated evidence for linkage at other regions.

Model of autism: increased ratio of excitation/inhibition in key neural systems

Autism is a severe neurobehavioral syndrome, arising largely as an inherited disorder, which can arise from several diseases. Despite recent advances in identifying some genes that can cause autism, its underlying neurological mechanisms are uncertain. Autism is best conceptualized by considering the neural systems that may be defective in autistic individuals. Recent advances in understanding neural systems that process sensory information, various types of memories and social and emotional behaviors are reviewed and compared with known abnormalities in autism. Then, specific genetic abnormalities that are linked with autism are examined. Synthesis of this information leads to a model that postulates that some forms of autism are caused by an increased ratio of excitation/inhibition in sensory, mnemonic, social and emotional systems. The model further postulates that the increased ratio of excitation/inhibition can be caused by combinatorial effects of genetic and environmental variables that impinge upon a given neural system. Furthermore, the model suggests potential therapeutic interventions.

Is fever suppression involved in the etiology of autism and neurodevelopmental disorders?

BACKGROUND

There appears to be a significant increase in the prevalence rate of autism. Reasons for the increase are unknown, however, there is a substantial body of evidence that suggests the etiology involves infections of the pregnant mother or of a young child. Most infections result in fever that is routinely controlled with antipyretics such as acetaminophen. The blocking of fever inhibits processes that evolved over millions of years to protect against microbial attack. Immune mechanisms in the central nervous system are part of this protective process.

HYPOTHESIS

The blockage of fever with antipyretics interferes with normal immunological development in the brain leading to neurodevelopmental disorders such as autism in certain genetically and immunologically disposed individuals.

TESTING THE HYPOTHESIS

Epidemiological studies to determine associations between the use of antipyretics and neurodevelopmental disorders should be undertaken. Biochemical tests will involve the examination of fluids/serum by mass spectrometry and the determination of cytokine/chemokine levels in serum and cell culture fluids after stimulation with fever-inducing molecules from bacteria, viruses and yeast. Postmortem brain can be examined by immunohistochemistry or other methods such as fluorescent in situ hybridization (FISH) to determine altered expression levels of chemokines/cytokines and other molecules.

IMPLICATIONS OF THE HYPOTHESIS

1) The use of antipyretics during pregnancy or in young children may be reserved for more severe fevers. 2) The perplexing genetic findings in autism may be better understood by categorizing genes along functional pathways. 3) New treatments based on immune, cell, pharmacological or even heat therapies may be developed.

Genetic and neurodevelopmental influences in autistic disorder

OBJECTIVE

In the past, autism was considered to be largely psychogenic. However, research in the last 2 decades indicates that autism is largely caused by genetic factors that lead to abnormal brain development. This article reviews research into the genetic and neurodevelopmental factors underlying autism.

METHODS

We review the findings from genetic and brain-imaging studies of autism over the past 15 years and synthesize these findings as a guide for future research.

RESULTS

Genome scans and association studies have suggested potential genomic regions and genes, respectively, that may be involved in the etiology of autism, and there have been some replications of these results. Similarly, the findings that brain volume is exaggerated in autism and corpus callosum size is reduced have also been independently replicated. Unfortunately, studies of other subcortical structures remain inconclusive or contradictory.

CONCLUSIONS

Overwhelming evidence now supports a neurobiological basis for autism. However, further refinements will be needed to guide future studies, particularly to identify the most informative phenotypes to investigate. Additionally, studies examining the role of genetic factors in the brain abnormalities underlying autism will likely lead to further findings that will enhance our understanding of autism's causes.

Prologue: Autism Spectrum Disorder

As the need for services for children with autism and related disorders has increased, so has the need for information about communication assessment and intervention for these children. Each of the articles in this forum considers essential knowledge for meeting the social, behavioral, and communication challenges presented by this population, as well as considerations for the individual variation noted within this population. It is hoped that the knowledge contained in this forum will provide interdisciplinary insight into the challenges of autism and related disorders and a research-based framework for making assessment and intervention decisions.