Subset of individuals with autism spectrum disorders and extreme macrocephaly associated with germline PTEN tumour suppressor gene mutations

The genetic aetiology of autism remains elusive. Occasionally, individuals with Cowden syndrome (a cancer syndrome) and other related hamartoma disorders such as Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like conditions, are characterised by germline PTEN mutations, and may have neurobehavioural features resembling autism as well as overgrowth and macrocephaly. Therefore, we undertook PTEN gene mutation analysis in 18 subjects mainly prospectively ascertained with autism spectrum disorder and macrocephaly. Of these 18 autistic subjects (13 males and five females; ages 3.1–18.4 years) with a head circumference range from 2.5 to 8.0 standard deviations above the mean, three males (17%) carried germline PTEN mutations. These three probands had previously undescribed PTEN mutations: H93R (exon 4), D252G (exon 7), and F241S (exon 7). They had the larger head circumference measurements amongst all our study subjects. The three residues altered in our patients were highly evolutionarily conserved. We suggest that PTEN gene testing be considered for patients with autistic behaviour and extreme macrocephaly. The gene findings may impact on recurrence risks as well as medical management for the patient.     

Multifactorial inheritance of non-syndromic macrocephaly

Objective: To reevaluate previous claims that non-syndromic macrocephaly is usually inherited as an autosomal dominant trait. Design: Head size was measured in the parents and sibs of children with non-syndromic macrocephaly. Outcome measures: If autosomal dominant inheritance is involved, the frequency distribution should be bimodal. Results: Head circumference of parents and sibs of the macrocephalic probands had a mean significantly greater than the population norm, and a unimodal distribution. Probands with psychomotor impairment had bigger heads, and more had a history of birth difficulty, than did unimpaired probands. Conclusions: The usual genetic basis for non-syndromic macrocephaly is multifactorial with a polygenic genetic basis, rather than autosomal dominant. Risk of recurrence appears to be much lower than if it would be on the assumption ot autosomal dominant inheritance. Macrocephaly in a parent or sib of an unborn child may present a risk for birth injury to that child. A larger series of patients will be necessary | to resolve this question.     

Relationship between head circumference and height in normal adults and in the nevoid basal cell carcinoma syndrome and neurofibromatosis type I

Occipitofrontal circumference (OFC) was strongly correlated with height in 72 normal Caucasian men (r = 0.28, P = 0.018) and 78 women (r = 0.53, P less than 0.0001). OFC:height ratios were approximately normally distributed in each sex with a mean of 0.326 (standard deviation [sd] = 0.0139) in males and 0.335 (sd = 0.0177) in females. Relative macrocephaly (an OFC greater than the 95th centile for height) was seen in seven of nine probands with the nevoid basal cell carcinoma syndrome (NBCC), eight of 32 non-probands with NBCC, three of four neurofibromatosis type 1 (NF1) probands, and six of nine non-probands with NF1. Thirty-one percent of the non-proband NBCC cases had OFC less than the 50th centile for height, while none of the NF1 cases had this finding. Head size appears to be related to proband status in NBCC, while the evidence suggests that NF1 is a true macrocephaly syndrome. Objective detection of relative abnormalities in head size may aid in syndrome delineation and diagnosis.     

Association of the oxytocin receptor gene (OXTR) in Caucasian children and adolescents with autism

The oxytocin receptor gene (OXTR) has been studied in autism because of the role of oxytocin (OT) in social cognition. Linkage has also been demonstrated to the region of OXTR in a large sample. Two single nucleotide polymorphisms (SNPs) and a haplotype constructed from them in OXTR have been associated with autism in the Chinese Han population. We tested whether these associations replicated in a Caucasian sample with strictly defined autistic disorder. We genotyped the two previously associated SNPs (rs2254298, rs53576) in 57 Caucasian autism trios. Probands met clinical, ADI-R, and ADOS criteria for autistic disorder. Significant association was detected at rs2254298 (p=0.03) but not rs53576. For rs2254298, overtransmission of the G allele to probands with autistic disorder was found which contrasts with the overtransmission of A previously reported in the Chinese Han sample. In both samples, G was more frequent than A. However, in our Caucasian autism trios and the CEU Caucasian HapMap samples the frequency of A was less than that reported in the Chinese Han and Chinese in Bejing HapMap samples. The haplotype test of association did not reveal excess transmission from parents to affected offspring. These findings provide support for association of OXTR with autism in a Caucasian population. Overtransmission of different alleles in different populations may be due to a different pattern of linkage disequilibrium between the marker rs2254298 and an as yet undetermined susceptibility variant in OXTR.     

Growth in stature and head circumference in high-functioning autism and Asperger disorder during the first 3 years of life

Little effort has been made to characterize the developmental anatomic phenotype of autism; although there is evidence of an increased head circumference and brain size, few other physical characteristics have been studied. The head circumference, body length/height, and weight measurements of infants, who were later diagnosed with high-functioning autism (HFA, n = 16) and Asperger disorder (AsD, n = 12), were extracted from health records over the first 3 years of life and compared to the measurements of a matched normal control group (n = 19). Using linear mixed-effects models, no differences were found in the average growth rate for head circumference, stature, or weight between the children with HFA and AsD. However, a significantly higher growth rate in body length/height and weight was found for the combined group of children with HFA and AsD compared to the normal control group. A trend toward higher growth rate in head circumference was also found among the former group. The results indicate that growth dysregulation in autism is not specific to the brain but also involves growth in stature.     

Autism,regression, and the broader autism phenotype

The broader autism phenotype (BAP) is a subclinical set of personality and other features that is thought to index familiality and/or genetic liability to autism. Eighteen parents of autistic probands with a history of language regression and 70 parents of autistic probands without regression were assessed for features of the BAP and compared with published rates in parents of nonautistic subjects. Parents of probands with regressive and nonregressive autism demonstrated similar rates of the BAP (27.8% vs. 32.9%; P = 0.33). The rate of the BAP was significantly higher in both groups of autism parents than in parents of nonautistic subjects (P < or = 0.01). Thus, this measure of genetic liability is increased equally in families with both forms of autism when compared with controls. Environmental events are therefore unlikely to be the sole cause of regressive autism in our sample. Environmental events, however, may act in an additive or "second-hit" fashion in individuals with a genetic vulnerability to autism.     

Autism,regression, and the broader autism phenotype

The broader autism phenotype (BAP) is a subclinical set of personality and other features that is thought to index familiality and/or genetic liability to autism. Eighteen parents of autistic probands with a history of language regression and 70 parents of autistic probands without regression were assessed for features of the BAP and compared with published rates in parents of nonautistic subjects. Parents of probands with regressive and nonregressive autism demonstrated similar rates of the BAP (27.8% vs. 32.9%; P = 0.33). The rate of the BAP was significantly higher in both groups of autism parents than in parents of nonautistic subjects (P ≤ 0.01). Thus, this measure of genetic liability is increased equally in families with both forms of autism when compared with controls. Environmental events are therefore unlikely to be the sole cause of regressive autism in our sample. Environmental events, however, may act in an additive or “second‐hit” fashion in individuals with a genetic vulnerability to autism. © 2002 Wiley‐Liss, Inc.     

The CHD8 overgrowth syndrome: A detailed evaluation of an emerging overgrowth phenotype in 27 patients

CHD8 has been reported as an autism susceptibility/intellectual disability gene but emerging evidence suggests that it additionally causes an overgrowth phenotype. This study reports 27 unrelated patients with pathogenic or likely pathogenic CHD8 variants (25 null variants, two missense variants) and a male:female ratio of 21:6 (3.5:1, p < .01). All patients presented with intellectual disability, with 85% in the mild or moderate range, and 85% had a height and/or head circumference ≥2 standard deviations above the mean, meeting our clinical criteria for overgrowth. Behavioral problems were reported in the majority of patients (78%), with over half (56%) either formally diagnosed with an autistic spectrum disorder or described as having autistic traits. Additional clinical features included neonatal hypotonia (33%), and less frequently seizures, pes planus, scoliosis, fifth finger clinodactyly, umbilical hernia, and glabellar hemangioma (≤15% each). These results suggest that, in addition to its established link with autism and intellectual disability, CHD8 causes an overgrowth phenotype, and should be considered in the differential diagnosis of patients presenting with increased height and/or head circumference in association with intellectual disability.     

Regional Callosal Morphology in Autism and Macrocephaly

Previous investigations have reported decreased size of the corpus callosum (CC) in autism. However, little is known of the regional distribution of these callosal abnormalities. Additional uncertainty exists regarding the role of head size with respect to variations in callosal size in individuals with autism. This study investigated the size of the CC in 5 groups of high functioning individuals: (1) normocephalic autistic individuals; (2) autism with macrocephaly; (3) non-autistic normocephalic controls; (4) non-autistic participants with benign macrocephaly; and (5) a reading disordered (RD) group, comprised of non-autistic individuals with a deficit in reading. The CC was traced from midsaggital MRIs and the outlines partitioned into 99 equidistant width measures. Factor analysis of the 99 widths revealed 10 contiguous callosal regions. Individuals with macrocephaly (autistic and non-autistic) had larger total CC size. Regional analysis revealed a significantly larger CC midbody in macrocephaly, regardless of presence or absence of autism. Within normocephalic individuals, those with autism had a smaller CC genu and midbody than either non-autistic controls or RD individuals. These results underscore the importance of considering head size in studies of CC morphology in autism. These findings add to the literature implicating problems of interhemispheric connectivity being present in individuals with autism.     

Regional callosal morphology in autism and macrocephaly

Previous investigations have reported decreased size of the corpus callosum (CC) in autism. However, little is known of the regional distribution of these callosal abnormalities. Additional uncertainty exists regarding the role of head size with respect to variations in callosal size in individuals with autism. This study investigated the size of the CC in 5 groups of high functioning individuals: (1) normocephalic autistic individuals; (2) autism with macrocephaly; (3) non-autistic normocephalic controls; (4) non-autistic participants with benign macrocephaly; and (5) a reading disordered (RD) group, comprised of non-autistic individuals with a deficit in reading. The CC was traced from midsaggital MRIs and the outlines partitioned into 99 equidistant width measures. Factor analysis of the 99 widths revealed 10 contiguous callosal regions. Individuals with macrocephaly (autistic and non-autistic) had larger total CC size. Regional analysis revealed a significantly larger CC midbody in macrocephaly, regardless of presence or absence of autism. Within normocephalic individuals, those with autism had a smaller CC genu and midbody than either non-autistic controls or RD individuals. These results underscore the importance of considering head size in studies of CC morphology in autism. These findings add to the literature implicating problems of interhemispheric connectivity being present in individuals with autism.     

Genetic testing in autism: how much is enough?

PurposeTo evaluate the yield of genetic testing in children with autism spectrum disorders.MethodsWe performed a retrospective chart review of 71 unrelated patients with a diagnosis of an isolated autism spectrum disorder seen in a genetics clinic over a period of 14 months. For most, referrals occurred after evaluation by a developmental pediatrician and/or psychologist to establish the diagnosis. Tiered laboratory testing for the majority of the patients followed a guideline that was developed in collaboration with clinicians at The Autism Center at Children's Hospital, Columbus, OH.ResultsThe patients included 57 males and 14 females; 57 met DSM-IV criteria for autism, with the rest being Asperger or pervasive developmental disorder not otherwise specified. Macrocephaly [head circumference (HC) ≥95%] was present in 19 (27%). Two children had visible chromosome abnormalities (47,XYY; 48,XY + 2mar/49,XY + 3mar). Two patients with autism and macrocephaly had heterozygous mutations in the PTEN tumor suppressor gene. Three females had Rett syndrome, each confirmed by DNA sequencing of the MECP2 gene. Extensive metabolic testing produced no positive results, nor did fragile X DNA testing.ConclusionThe overall diagnostic yield was 10% (7/71). PTEN gene sequencing should be considered in any child with macrocephaly and autism or developmental delay. Metabolic screening may not be warranted in autism spectrum disorders without more specific indications or additional findings.     

Personality and language characteristics in parents from multiple-incidence autism families

Several studies have suggested that the genetic liability for autism may be expressed in non-autistic relatives of autistic probands, in behavioral characteristics that are milder but qualitatively similar to the defining features of autism. We employ a variety of direct assessment approaches to examine both personality and language in parents ascertained through having two autistic children (multiple-incidence autism parents) and parents of Down syndrome probands. Multiple-incidence autism parents had higher rates of particular personality characteristics (rigidity, aloofness, hypersensitivity to criticism, and anxiousness), speech and pragmatic language deficits, and more limited friendships than parents in the comparison group. The implications of these findings for future genetic studies of autism are discussed. Am. J. Med. Genet. 74:398–411, 1997. © 1997 Wiley-Liss, Inc.     

Assessment of head size adjusted for height: an anthropometric tool for clinical use based on Argentinian data

BACKGROUND: Relative macrocephaly describes a large head in relation to stature, and this indicator could be helpful in depicting syndromes with large heads and short stature, providing the existence of some relationship between both measurements in normal children. OBJECTIVE: The aims of this study were (1) to evaluate the existence of a relationship between head circumference (HC), height and weight, (2) to build an instrument for evaluating it and validate its clinical utility. SUBJECTS AND METHODS: Relationship between HC, height and weight was explored in a national sample of 3571 healthy, well nourished boys and girls aged 0-5.99 years. Age-adjusted correlation coefficients calculated were: HC and height, 0.30; HC and weight, 0.37; and height and weight, 0.60. A growth standard of HC to height ratio was constructed using the LMS method with both sexes pooled, and selected centiles and SD scores of HC to height ratio for each age were estimated. Z-scores of HC for age, and HC to height ratio were calculated for 13 children with hypochondroplasia, and 90 with achondroplasia, both conditions associated with macrocephaly. RESULTS: Only four children with hypochondroplasia had HC for age above 2.00 SD, whereas all of them showed SD scores above 2.00 when the HC to height ratio was evaluated. Results suggest that the prepared standard may be of clinical utility. CONCLUSIONS: A new standard is proposed, capable of pinpointing children with relative macrocephaly.     

Phenotype-to-genotype approach reveals head-circumference-associated genes in an autism spectrum disorder cohort

The genotype-first approach has been successfully applied and has elucidated several subtypes of autism spectrum disorder (ASD). However, it requires very large cohorts because of the extensive genetic heterogeneity. We investigate the alternate possibility of whether phenotype-specific genes can be identified from a small group of patients with specific phenotype(s). To identify novel genes associated with ASD and abnormal head circumference using a phenotype-to-genotype approach, we performed whole-exome sequencing on 67 families with ASD and abnormal head circumference. Clinically relevant pathogenic or likely pathogenic variants account for 23.9% of patients with microcephaly or macrocephaly, and 81.25% of those variants or genes are head-size associated. Significantly, recurrent pathogenic mutations were identified in two macrocephaly genes (PTEN, CHD8) in this small cohort. De novo mutations in several candidate genes (UBN2, BIRC6, SYNE1, and KCNMA1) were detected, as well as one new candidate gene (TNPO3) implicated in ASD and related neurodevelopmental disorders. We identify genotype-phenotype correlations for head-size-associated ASD genes and novel candidate genes for further investigation. Our results also suggest a phenotype-to-genotype strategy would accelerate the elucidation of genotype-phenotype relationships for ASD by using phenotype-restricted cohorts.     

Brain anatomy in non-affected parents of autistic probands: a MRI study

BACKGROUND: Autism is a neurodevelopmental disorder with an estimated genetic origin of 90%. Previous studies have reported an increase in brain volume of approximately 5% in autistic subjects, especially in children. If this increase in brain volume is genetically determined, biological parents of autistic probands might be expected to show brain enlargement, or at least intracranial enlargement, as well. Identifying structural brain abnormalities under genetic control is of particular importance as these could represent endophenotypes of autism. METHOD: Using quantitative anatomic brain magnetic resonance imaging, volumes of intracranial, total brain, frontal, parietal, temporal and occipital lobe, cerebral and cortical gray and white matter, cerebellum, lateral ventricle, and third ventricle were measured in biological, non-affected parents of autistic probands (19 couples) and in healthy, closely matched control subjects (20 couples). RESULTS: No significant differences were found between the parents of the autistic probands and healthy control couples in any of the brain volumes. Adding gender as a factor in a second analysis did not reveal a significant interaction effect of gender by group. CONCLUSIONS: The present sample of biological, non-affected parents of autistic probands did not show brain enlargements. As the intracranium is not enlarged, it is unlikely that the brain volumes of the parents of autistic probands have originally been enlarged and have been normalized. Thus, increased brain volume in autism might be caused by the interaction of paternal and maternal genes, possibly with an additional effect of environmental factors, or increased brain volumes might reflect phenotypes of autism.     

Cole-Hughes macrocephaly syndrome and associated autistic manifestations

Based on cases that had been excluded from a previous clinical study of Sotos syndrome, Cole and Hughes [1991: Am J Med Genet 41:115-124] reported a new syndrome associated with marked obesity, occasional delayed bone age, distinctive facial anomalies, mental retardation, and progressive postnatal macrocephaly in the context of autosomal dominant familial macrocephaly. Subsequently, Stevenson et al. [1997: Lancet 349:1744-1745] emphasized the association of progressive postnatal macrocephaly with autism, and they suggested that this might comprise a recognizable autism syndrome. We report two additional patients with Cole-Hughes syndrome and associated autistic characteristics with attention deficit hyperactivity disorder. These patients seem to manifest a distinctive behavioral phenotype associated with Cole-Hughes syndrome and they manifest a distinct subgroup of persons with autism that may ultimately shed light on the pathogenesis of this disorder.     

Three probands with autistic disorder and isodicentric chromosome 15

We have identified three unrelated probands with autistic disorder (AD) and isodicentric chromosomes that encompass the proximal region of 15q11.2. All three probands met the Diagnostic and Statistical Manual of Mental Disorders, fourth edition [DSM-IV; American Psychiatric Association, 1994], and International Classification of Diseases ( ICD-10) diagnostic criteria for AD, confirmed with the Autism Diagnostic Interview -Revised (ADI-R). Chromosome analysis revealed the following karyotypes: 47,XX,+idic(15)(q11.2), 47,XX, +idic(15) (q11.2), and 47,XY,+idic(15)(q11.2). Haplotype analysis of genotypic maker data in the probands and their parents showed that marker chromosomes in all three instances were of maternal origin. Comparison of the clinical findings of the three AD probands with case reports in the published literature (N = 20) reveals a clustering of physical and developmental features. Specifically, these three probands and the majority of reported probands in the literature exhibited hypotonia (n = 13), seizures (n = 13), and delayed gross motor development (n = 13). In addition, clustering of the following clinical signs was seen with respect to exhibited speech delay (n = 13), lack of social reciprocity (n = 11), and stereotyped behaviors (n = 12). Collectively, these data provide further evidence for the involvement of chromosome 15 in AD as well as present preliminary data suggesting a clustering of clinical features in AD probands with proximal 15q anomalies.     

Biochemical screening and PTEN mutation analysis in individuals with autism spectrum disorders and macrocephaly

Unlike some other childhood neurodevelopmental disorders, no diagnostic biochemical marker has been identified in all individuals with an autism spectrum disorder (ASD). This deficit likely results from genetic heterogeneity among the population. Therefore, we evaluated a subset of individuals with ASDs, specifically, individuals with or without macrocephaly in the presence or absence of PTEN mutations. We sought to determine if amino or organic acid markers could be used to identify individuals with ASDs with or without macrocephaly in the presence or absence of PTEN mutations, and to establish the degree of macrocephaly in individuals with ASDs and PTEN mutation. Urine, blood and occipital–frontal circumference (OFC) measurements were collected from 69 individuals meeting DSM-IV-TR criteria. Urine and plasma samples were subjected to amino and organic acid analyses. PTEN was Sanger-sequenced from germline genomic DNA. Germline PTEN mutations were identified in 27% (6/22) of the macrocephalic ASD population. All six PTEN mutation-positive individuals were macrocephalic with average OFC+4.35 standard deviations (SDs) above the mean. No common biochemical abnormalities were identified in macrocephalic ASD individuals with or without PTEN mutations. In contrast, among the collective ASD population, elevation of urine aspartic acid (87% 54/62), plasma taurine (69% 46/67) and reduction of plasma cystine (72% 46/64) were observed. PTEN sequencing should be carried out for all individuals with ASDs and macrocephaly with OFC ≥2SDs above the mean. A proportion of individuals with ASDs may have an underlying disorder in sulfur amino acid metabolism.     

Social behavior profile in young males with fragile X syndrome: characteristics and specificity

The present study characterizes distinctive and specific features of social behavior impairment, termed social behavior profile (SBP), in young males with fragile X syndrome (FraX). Fourteen males with FraX and autism (FraX+Aut), ages 3-8 years, were compared with either 41 FraX boys without autism (Aut), 7 age-matched males with developmental language delay and autism (DLD+Aut), or with 11 boys with non-selected (for language delay) idiopathic autism (IA), on several standardized instruments assessing social behavior and autistic features (i.e., autism diagnostic interview-revised, ADI-R). We found that FraX+Aut subjects displayed more impairment in overall cognition, problem/aberrant behavior, and adaptive behavior than the rest of the FraX cohort, even when individuals with pervasive developmental disorder (PDD) were included in the latter. Compared to both DLD+Aut and IA, FraX+Aut males were less impaired in ADI-R reciprocal social interaction (RECS) domain. However, boys with FraX+Aut were in general comparable to DLD+Aut subjects in problem/aberrant and adaptive behaviors. Based on the contrast between FraX+Aut and non-autistic FraX and DLD+Aut, we were able to identify measures (e.g., child behavior checklist (CBCL) withdrawn subscale) that better define social interaction impairment in FraX. Comparisons with DLD+Aut and IA led to the conclusion that communication impairment (COMM) and stereotypic behavior contribute relatively more to the diagnosis of autism in FraX+Aut. In agreement with recent studies, our data suggest that FraX+Aut, and more generally SBP, is a distinctive subphenotype among boys with FraX, which may share some pathophysiological mechanisms with IA.     

Head circumference is an independent clinical finding associated with autism

Occipitofrontal circumference (OFC) is one of the few physical findings in autism that varies significantly from the norm and is distinct and measurable. As part of a study of genetic heterogeneity of autism, we scrutinized data from a large sample of patients with idiopathic autism (N = 137), using OFC as the categorizing variable. The OFC standard deviation (OFCSD) values of the autistic propositi (0.61+/-1.6) varied significantly from that of the normal population (0.0+/-1.0), (P<0.001). Comparison of the macrocephalic (OFCSD > 2.0, N = 32) with the normocephalic individuals (-2 SD < OFCSD < +2 SD, N = 95) showed no significant differences in sex ratio, morphological status, IQ, seizure prevalence, or recurrence risks. The macrocephalic individuals were slightly less apt than those with normocephaly to have a family history of Attention Deficit Hyperactivity Disorder (ADHD) (P<0.05). Each clinical subgroup of autism propositi, defined on the basis of phenotypic status, type of onset, seizure history, or IQ, had a higher than normal mean OFC indicating that macrocephaly is an independent clinical trait in autism. As in the non-autistic population, macrocephaly was highly familial with 45% of the macrocephalic and 37% of the normocephalic propositi having at least one macrocephalic parent. Microcephaly, however, was an independent significant variable that predicted the presence of other phenotypic or genetic traits and outcome. The microcephalic patients were more likely to have abnormal physical morphology, structural brain malformations, lower IQ, and seizures. Their sex ratio was closer to normal, and their relatives had a higher incidence of seizures.