Autism Spectrum Disorder in an Unselected Cohort of Children with Neurofibromatosis Type 1 (NF1)

The effect of lamotrigine on cortical inhibition and plasticity in Neurofibromatosis type 1: Exploratory analysis of a randomized controlled trial (NF1-EXCEL)

OBJECTIVE

Neurofibromatosis type 1 (NF1) is a genetic disorder associated with cognitive and behavioral deficits. In NF1, decreased neurofibromin levels attenuate hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) activity, thereby increasing inhibitory interneuron activity and decreasing synaptic plasticity. Lamotrigine, an HCN1-agonist, rescued this electrophysiological phenotype in an NF1 mouse model. We investigated whether lamotrigine can alter cortical inhibition and plasticity in adolescents with NF1 using transcranial magnetic stimulation (TMS).

METHODS

We performed an explorative analysis of secondary outcomes in the NF1-EXCEL trial (Clinicaltrials.gov identifier NCT02256124). Thirty-one adolescents with NF1 were randomized to either receive lamotrigine or a placebo. Using TMS, cortical inhibition was assessed with short-interval intracortical inhibition (SICI) and cortical plasticity with paired associative stimulation (PAS) at baseline and after 10 weeks of intervention.

RESULTS

Lamotrigine did not affect baseline cortical excitability. Additionally, no significant effects on either SICI or PAS responses were found after lamotrigine treatment in adolescents with NF1. Finally, lamotrigine did not affect pre-PAS single-pulse cortical excitability measures.

CONCLUSION

10-week lamotrigine treatment does not alter cortical inhibition and plasticity in adolescents with NF1.

SIGNIFICANCE

While limited by a small sample size, our study indicates that lamotrigine cannot consistently modulate SICI or PAS in adolescents with NF1, suggesting limited potential for treating the underlying pathophysiological mechanisms.

Neurofibromin Deficiency Alters the Patterning and Prioritization of Motor Behaviors in a State-Dependent Manner

Genetic disorders such as neurofibromatosis type 1 (Nf1) increase vulnerability to cognitive and behavioral disorders, such as autism spectrum disorder and attention-deficit/hyperactivity disorder. Nf1 results from mutations in the neurofibromin gene that can reduce levels of the neurofibromin protein. While the mechanisms have yet to be fully elucidated, loss of Nf1 may alter neuronal circuit activity leading to changes in behavior and susceptibility to cognitive and behavioral comorbidities. Here we show that mutations decreasing Nf1 expression alter motor behaviors, impacting the patterning, prioritization, and behavioral state dependence in a Drosophila model of Nf1. Loss of Nf1 increased spontaneous grooming in male and female flies. This followed a nonlinear spatial pattern, with Nf1 deficiency increasing grooming of certain body parts differentially, including the abdomen, head, and wings. The increase in grooming could be overridden by hunger in foraging animals, demonstrating that the Nf1 effect is plastic and internal state dependent. Stimulus-evoked grooming patterns were altered as well, suggesting that hierarchical recruitment of grooming command circuits was altered. Yet loss of Nf1 in sensory neurons and/or grooming command neurons did not alter grooming frequency, suggesting that Nf1 affects grooming via higher-order circuit alterations. Changes in grooming coincided with alterations in walking. Flies lacking Nf1 walked with increased forward velocity on a spherical treadmill, yet there was no detectable change in leg kinematics or gait. These results demonstrate that loss of Nf1 alters the patterning and prioritization of repetitive behaviors, in a state-dependent manner, without affecting low-level motor functions.

Lamotrigine for cognitive deficits associated with neurofibromatosis type 1: A phase II randomized placebo-controlled trial

AIM

To find proof-of-principle evidence for short-term treatment with lamotrigine to improve cognitive functioning of adolescents with neurofibromatosis type 1 (NF1).

METHOD

This was a double-blind, parallel-group, randomized, placebo-controlled clinical trial (the NF1-EXCEL trial: Examining the Cognitive and Electrophysiological benefit of Lamotrigine in Neurofibromatosis type 1; Clinicaltrials.gov identifier NCT02256124), with the aim of enrolling 60 adolescents with NF1 aged 12 to 17  years 6 months. The short-term study intervention was 200 mg of lamotrigine taken orally for 26 weeks. The primary outcome was performance IQ tested with the Wechsler Intelligence Scale for Children, Third Edition, complemented with secondary outcomes for visuospatial learning efficacy, visual perception, visual sustained attention, fine motor coordination, attention-deficit/hyperactivity problems, and executive functioning.

RESULTS

We screened 402 adolescents with NF1, of whom 31 (eight females) entered the study. Complete-case analysis showed no effect of lamotrigine on either performance IQ (-0.23, 95% CI -6.90 to 6.44) or most secondary outcomes. Visual sustained attention showed a trend towards better performance in the lamotrigine group (-0.81, 95% CI -1.67 to 0.04).

INTERPRETATION

Lamotrigine did not improve cognitive functioning in adolescents with NF1. The small treatment effects make it unlikely that a larger sample size could have changed this conclusion.

Social Communication in Ras Pathway Disorders: A Comprehensive Review From Genetics to Behavior in Neurofibromatosis Type 1 and Noonan Syndrome

Neurofibromatosis type 1 (NF1) and Noonan syndrome (NS) are neurogenetic syndromes caused by pathogenetic variants encoding components of the Ras-ERK-MAPK (Ras/extracellular signal-regulated kinase/mitogen-activated protein kinase) signaling pathway (Ras pathway). NF1 and NS are associated with differences in social communication and related neuropsychiatric risks. During the last decade, there has been growing interest in Ras-linked syndromes as models to understand social communication deficits and autism spectrum disorder. We systematically review the literature between 2010 and 2023 focusing on the social communication construct of the Research Domain Criteria framework. We provide an integrative summary of the research on facial and nonfacial social communication processes in NF1 and NS across molecular, cellular, neural circuitry, and behavioral domains. At the molecular and cellular levels, dysregulation in the Ras pathway is intricately tied to variations in social communication through changes in GABAergic (gamma-aminobutyric acidergic), glutamatergic, and serotonergic transmission, as well as inhibitory/excitatory imbalance. Neural circuitry typically associated with learning, attention, and memory in NF1 and NS (e.g., corticostriatal connectivity) is also implicated in social communication. We highlight less-researched potential mechanisms for social communication, such as white matter connectivity and the default mode network. Finally, key gaps in NF1 and NS literature are identified, and a roadmap for future research is provided. By leveraging genetic syndrome research, we can understand the mechanisms associated with behaviors and psychiatric disorders.

Expanding the phenotype of neurofibromatosis type 1 microdeletion syndrome

Neurofibromatosis type 1 (NF-1) microdeletion syndrome accounts for 5 to 11% of individuals with NF-1. The aim of our study was to characterize a large cohort of individuals with NF-1 microdeletion syndrome and expand its natural history. We conducted a retrospective chart review from 1994 to 2024 of individuals with NF-1 microdeletion syndrome followed at two large Neurofibromatosis Clinics. This cohort consists of 57 individuals with NF-1 microdeletion syndrome (28 type-1, 4 type-2, 2 type-3, 9 atypical deletions, and 14 indeterminate). We note 38/56 (67.9%) with describable facial features, 25/57 (43.8%) with plexiform neurofibromas, and 3/57 (5.2%) with malignant peripheral nerve sheath tumors within the observed period. The most reported neurodevelopmental manifestations from school-age or older individuals included 39/49 (79.6%) with developmental delays, 35/49 (71.4%) with expressive and/or receptive speech delays, 33/41 (80.5%) with learning difficulties, and 23/42 (54.8%) with attention-deficit/hyperactivity disorder. Full-scale IQ testing data was available for 22 individuals (range: 50-96). Of the 21 adults in this cohort, 14/21 (66.7%) graduated from high school, and 4/21 (19.0%) had some college experience. Many individuals received academic support (i.e., special education, individual education plan). In this cohort, neurocognitive outcomes in adults varied more than typically reported in the literature.

Autism Spectrum Disorder Symptom Profiles in Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis Complex and Neurofibromatosis Type 1

Studying Autism Spectrum Disorder (ASD) heterogeneity in biologically homogeneous samples may increase our knowledge of ASD etiology. Fragile X syndrome (FXS), Angelman syndrome (AS), Tuberous Sclerosis Complex (TSC), and Neurofibromatosis type 1 (NF1) are monogenic disorders with high a prevalence of ASD symptomatology. This study aimed to identify ASD symptom profiles in a large group of children and adolescents (0;9-28 years) with FXS, AS, TSC, and NF1. Data on ASD symptomatology (Autism Diagnostic Observation Scale (ADOS-2) & Social Responsiveness Scale (SRS-2)) were collected from children and adolescents with FXS (n = 54), AS (n = 93), TSC (n = 112), and NF1 (n = 278). To identify groups of individuals with similar ASD profiles, we performed two latent profile analyses. We identified a four-profile model based on the ADOS-2, with a (1) 'Non-spectrum symptom profile', (2) 'Social Affect symptom profile', (3)'Restricted/Repetitive Behaviors symptom profile', and (4)'ASD symptom profile'. We also identified a four-profile model based on the SRS, with a (1)'Non-clinical symptom profile', (2)'Mild symptom profile', (3)'Moderate symptom profile', and (4)'Severe symptom profile'. Although each syndrome group exhibited varying degrees of severity, they also displayed heterogeneity in the profiles in which they were classified. We found distinct ASD symptom profiles in a population consisting of children and adolescents with FXS, AS, TSC, and NF1. Our study highlights the importance of a personalized approach to the identification and management of ASD symptoms in rare genetic syndromes. Future studies should aim to include more domains of functioning and investigate the stability of latent profiles over time.

Neurofibromin deficiency alters the patterning and prioritization of motor behaviors in a state-dependent manner

Genetic disorders such as neurofibromatosis type 1 increase vulnerability to cognitive and behavioral disorders, such as autism spectrum disorder and attention-deficit/hyperactivity disorder. Neurofibromatosis type 1 results from loss-of-function mutations in the neurofibromin gene and subsequent reduction in the neurofibromin protein (Nf1). While the mechanisms have yet to be fully elucidated, loss of Nf1 may alter neuronal circuit activity leading to changes in behavior and susceptibility to cognitive and behavioral comorbidities. Here we show that mutations decreasing Nf1 expression alter motor behaviors, impacting the patterning, prioritization, and behavioral state dependence in a Drosophila model of neurofibromatosis type 1. Loss of Nf1 increases spontaneous grooming in a nonlinear spatial and temporal pattern, differentially increasing grooming of certain body parts, including the abdomen, head, and wings. This increase in grooming could be overridden by hunger in food-deprived foraging animals, demonstrating that the Nf1 effect is plastic and internal state-dependent. Stimulus-evoked grooming patterns were altered as well, with nf1 mutants exhibiting reductions in wing grooming when coated with dust, suggesting that hierarchical recruitment of grooming command circuits was altered. Yet loss of Nf1 in sensory neurons and/or grooming command neurons did not alter grooming frequency, suggesting that Nf1 affects grooming via higher-order circuit alterations. Changes in grooming coincided with alterations in walking. Flies lacking Nf1 walked with increased forward velocity on a spherical treadmill, yet there was no detectable change in leg kinematics or gait. Thus, loss of Nf1 alters motor function without affecting overall motor coordination, in contrast to other genetic disorders that impair coordination. Overall, these results demonstrate that loss of Nf1 alters the patterning and prioritization of repetitive behaviors, in a state-dependent manner, without affecting motor coordination.

Social challenges, autism spectrum disorder, and attention deficit/hyperactivity disorder in youth with neurofibromatosis type I

OBJECTIVE

Youth with neurofibromatosis type I (NF1) demonstrate high rates of Autism Spectrum Disorder (ASD) and Attention Deficit/Hyperactivity Disorder (ADHD), which often have overlapping behaviors. Diagnostic clarity is important to guide services. This study evaluated ASD classification in NF1 using various methods and whether those with ADHD suspicion have more social challenges associated with ASD.

METHOD

34 youth with NF1 (Mage = 10.5 ± 1.6 years), completed ASD assessments that combined direct observation and informant ratings to yield a Clinician Best Estimate (CBE) classification. Caregivers rated ASD-related social challenges using the Social Responsiveness Scale- 2nd Edition (SRS-2).

RESULTS

ASD classification varied depending on the method, ranging from 32% using low-threshold SRS-2 cut-scores (T ≥ 60) to under 6% when combining cut scores for diagnostic observational tools and stringent SRS-2 cut-scores (T ≥ 70). 14.7% had a CBE ASD classification. 44% were judged to have autism traits associated with a non-ASD diagnosis. The 52.9% with a suspicion of ADHD had higher SRS-2 scores than those without ADHD, F (7, 26) = 3.45, p < .05, Wilk's lambda = 0.518, partial eta squared = 0.482.

CONCLUSIONS

Findings highlight the importance of rigorous diagnostic methodology when evaluating ASD in NF1 to inform the selection of targeted interventions for socialization challenges in NF1.

Social cognition in children with neurofibromatosis type 1

INTRODUCTION

Neurofibromatosis type 1 (NF1) is a genetic pathology that can lead to impaired social functioning that has a negative impact on patients' quality of life. To date, although the hypothesis of impaired social cognition has been proposed as a potential explanation for these difficulties, very few studies have focused on theory of mind in children with NF1. Furthermore, other complex sociocognitive abilities have never been investigated. The aim of the present study was to assess theory of mind, moral reasoning, and social information processing in children with NF1 compared with a control group.

METHOD

We administered the Paediatric Evaluation of Emotions, Relationships and Socialization® to 38 children with NF1 aged between 8 years and 16 years 11 months (mean = 11.4, SD = 2.3) and 43 control children with comparable sociodemographic characteristics.

RESULTS

Patients performed significantly worse than controls on moral reasoning and social information processing tests, but there was no significant difference on theory of mind.

CONCLUSIONS

These results seem to confirm the presence of social cognition difficulties in NF1 that could explain, at least in part, their social difficulties, although not all dimensions are concerned. The differences between the processes we assessed are discussed in relation to the methodologies used to measure them, and raises questions about the complementarity of traditional tools and more ecological assessments.

Neuropsychiatric phenotypes in children with Noonan syndrome

AIM

We investigated neuropsychiatric outcomes in children with Noonan syndrome and addressed limitations in previous research with a focus on prepubertal children, comparison to typically developing children, comprehensive neuropsychiatric evaluation, and controlling for overall cognitive abilities.

METHOD

Forty-five children with Noonan syndrome (mean = 8 years 6 months, SD = 2 years 2 months; 29 females) and 40 typically developing children (mean = 8 years 9 months, SD = 2 years; 22 females) were evaluated with objective, parent-report, and psychiatric interview measures.

RESULTS

Children with Noonan syndrome demonstrated elevated symptoms across attention-deficit/hyperactivity disorder (ADHD) (attention, hyperactivity, and inhibition), autism spectrum disorder (ASD) (maintaining social relationships, behavioral rigidity, and sensory sensitivity), and oppositional defiant disorder (ODD) (aggression) symptom clusters relative to typically developing children (all p < 0.05). Group differences in nearly all parent-report measures were significant after accounting for variations in intellectual functioning, suggesting that increased neurodevelopmental symptoms are not simply driven by overall intelligence. Twenty out of 42 children with Noonan syndrome met criteria for ADHD, eight out of 42 for ODD, and 11 out of 43 demonstrated clinically significant symptoms seen in children with ASD.

INTERPRETATION

Children with Noonan syndrome are at increased risk for a range of ADHD, ASD, and ODD associated symptoms. A dimensional approach reveals significant ASD symptoms in Noonan syndrome that do not emerge when using the currently accepted categorical diagnostic approach.

WHAT THIS PAPER ADDS

Neuropsychiatric disorders occur in more than half of children with Noonan syndrome. Children with Noonan syndrome demonstrate highly variable neurodevelopmental symptom profiles. Children with Noonan syndrome display variable impairments in attention, hyperactivity, and inhibition. Specific social concerns include behavioral rigidity, transitions, and difficulties maintaining social relationships. Children with Noonan syndrome display variably elevated levels of aggression and emotional dysregulation.

Psychosocial implications of rare genetic skin diseases affecting appearance on daily life experiences, emotional state, self-perception and quality of life in adults: a systematic review

BACKGROUND

Since the beginning of human genetic research, there are very few publications sharing insights of the negative impact of rare genetic skin diseases (RGSD) on patients' experiences. This systematic review assessed the psychosocial implications of these conditions in terms of daily life experiences, emotional state, self-perception, and Quality of Life (QoL).

METHODOLOGY

A systematic review was carried out on albinism, neurofibromatosis type 1 (NF1), birthmarks and inherited ichthyosis. The PubMed, Scopus, PsycArticle, PsychInfo, Psychology and Behavioral Sciences Collection, and SOCindex databases were queried. Inclusion criteria were adult patients with one of these RGSDs. Simple descriptive statistics and qualitative content analysis were conducted to summarize the main results reported by the authors.

RESULTS

Of the 9987 articles retrieved, 48 articles were included: albinism (16), NF1 (16), inherited ichthyosis (10), birthmarks (6). The majority of the studies on albinism were conducted in Africa. Twenty-seven studies quantitatively assessed diverse psychological parameters: 13 showed a significant impact of the disease on QoL, five on emotional state, two on self-representation and two others on psychiatric comorbidities. Disease severity and visibility were good predictors of QoL (except for albinism). Body image and appearance concerns were also associated with QoL and emotional state. The 19 qualitative studies highlighted recurring themes across each of these diseases: discrimination and stigma during childhood and adolescence, discomfort in social interactions, guilt of transmission, the importance of social support from family and friends, altered daily life functioning, altered romantic and sex life, limited academic and professional aspirations, lack of interest and support from the medical field, and the unpredictability of the evolution of the disease. The only two mixed-method studies in this review were unable to contribute to any inferential analyses but could corroborate some of the qualitative findings.

CONCLUSION

These results showed that RGSDs have a significant impact on different aspects of patients' lives. This review has demonstrated that there is a real need for support systems for patients with these diseases. Such systems should be developed to provide them with necessary information and to guide them through an appropriate care pathway.

Genetic diagnostic yields of 354 Chinese ASD children with rare mutations by a pipeline of genomic tests

Purpose: To establish an effective genomic diagnosis pipeline for children with autism spectrum disorder (ASD) for its genetic etiology and intervention. Methods: A cohort of 354 autism spectrum disorder patients were obtained from Beijing Children's Hospital, Capital Medical University. Peripheral blood samples of the patients were collected for whole genome sequencing (WGS) and RNA sequencing (RNAseq). Sequencing data analyses were performed for mining the single nucleotide variation (SNV), copy number variation (CNV) and structural variation (SV). Sanger sequencing and quantitative PCR were used to verify the positive results. Results: Among 354 patients, 9 cases with pathogenic/likely pathogenic copy number variation and 10 cases with pathogenic/likely pathogenic single nucleotide variations were detected, with a total positive rate of 5.3%. Among these 9 copy number variation cases, 5 were de novo and 4 were inherited. Among the 10 de novo single nucleotide variations, 7 were previously unreported. The pathological de novo mutations account for 4.2% in our cohort. Conclusion: Rare mutations of copy number variations and single nucleotide variations account for a relatively small proportion of autism spectrum disorder children, which can be easily detected by a genomic testing pipeline of combined whole genome sequencing and RNA sequencing. This is important for early etiological diagnosis and precise management of autism spectrum disorder with rare mutations.

Loss of NF1 in Drosophila Larvae Causes Tactile Hypersensitivity and Impaired Synaptic Transmission at the Neuromuscular Junction

Autism spectrum disorder (ASD) is a neurodevelopmental condition in which the mechanisms underlying its core symptomatology are largely unknown. Studying animal models of monogenic syndromes associated with ASD, such as neurofibromatosis type 1 (NF1), can offer insights into its etiology. Here, we show that loss of function of the Drosophila NF1 ortholog results in tactile hypersensitivity following brief mechanical stimulation in the larva (mixed sexes), paralleling the sensory abnormalities observed in individuals with ASD. Mutant larvae also exhibit synaptic transmission deficits at the glutamatergic neuromuscular junction (NMJ), with increased spontaneous but reduced evoked release. While the latter is homeostatically compensated for by a postsynaptic increase in input resistance, the former is consistent with neuronal hyperexcitability. Indeed, diminished expression of NF1 specifically within central cholinergic neurons induces both excessive neuronal firing and tactile hypersensitivity, suggesting the two may be linked. Furthermore, both impaired synaptic transmission and behavioral deficits are fully rescued via knock-down of Ras proteins. These findings validate NF1 -/- Drosophila as a tractable model of ASD with the potential to elucidate important pathophysiological mechanisms.SIGNIFICANCE STATEMENT Autism spectrum disorder (ASD) affects 1-2% of the overall population and can considerably impact an individual's quality of life. However, there are currently no treatments available for its core symptoms, largely because of a poor understanding of the underlying mechanisms involved. Examining how loss of function of the ASD-associated NF1 gene affects behavior and physiology in Drosophila may shed light on this. In this study, we identify a novel, ASD-relevant behavioral phenotype in NF1 -/- larvae, namely an enhanced response to mechanical stimulation, which is associated with Ras-dependent synaptic transmission deficits indicative of neuronal hyperexcitability. Such insights support the use of Drosophila neurofibromatosis type 1 (NF1) models in ASD research and may provide outputs for genetic or pharmacological screens in future studies.

Cerebellum-dependent associative learning is not impaired in a mouse model of neurofibromatosis type 1

Individuals with Neurofibromatosis type 1 (NF1) experience a high degree of motor problems. The cerebellum plays a pivotal role in motor functioning and the NF1 gene is highly expressed in cerebellar Purkinje cells. However, it is not well understood to what extent NF1 affects cerebellar functioning and how this relates to NF1 motor functioning. Therefore, we subjected global Nf1^+/- mice to a cerebellum-dependent associative learning task, called Pavlovian eyeblink conditioning. Additionally, we assessed general motor function and muscle strength in Nf1^+/- mice. To our surprise, we found that Nf1^+/- mice showed a moderately increased learning rate of conditioned eyeblink responses, as well as improved accuracy in the adaptive timing of the eyeblink responses. Locomotion, balance, general motor function, and muscle strength were not affected in Nf1^+/- mice. Together, our results support the view that cerebellar function in Nf1^+/- mice is unimpaired.

Mechanistic insights from animal models of neurofibromatosis type 1 cognitive impairment

Neurofibromatosis type 1 (NF1) is an autosomal-dominant neurogenetic disorder caused by mutations in the gene neurofibromin 1 (NF1). NF1 predisposes individuals to a variety of symptoms, including peripheral nerve tumors, brain tumors and cognitive dysfunction. Cognitive deficits can negatively impact patient quality of life, especially the social and academic development of children. The neurofibromin protein influences neural circuits via diverse cellular signaling pathways, including through RAS, cAMP and dopamine signaling. Although animal models have been useful in identifying cellular and molecular mechanisms that regulate NF1-dependent behaviors, translating these discoveries into effective treatments has proven difficult. Clinical trials measuring cognitive outcomes in patients with NF1 have mainly targeted RAS signaling but, unfortunately, resulted in limited success. In this Review, we provide an overview of the structure and function of neurofibromin, and evaluate several cellular and molecular mechanisms underlying neurofibromin-dependent cognitive function, which have recently been delineated in animal models. A better understanding of neurofibromin roles in the development and function of the nervous system will be crucial for identifying new therapeutic targets for the various cognitive domains affected by NF1.

Summary: Neurofibromin influences neural circuits through RAS, cAMP and dopamine signaling. Exploring the mechanisms underlying neurofibromin-dependent behaviors in animal models might enable future treatment of the various cognitive deficits that are associated with neurofibromatosis type 1.

Sex- and age-related differences in autistic behaviours in children with neurofibromatosis type 1

This study investigated sex and age differences in autistic behaviours in children with neurofibromatosis type 1 (NF1) who scored within the clinical range on the Social Responsiveness Scale - Second Edition (T score ≥ 60). Thirty-four males and 28 females (3-16 years) were assessed with the Autism Diagnostic Observation Schedule - Second Edition and Autism Diagnostic Interview - Revised. Across both measures, males exhibited greater social communication deficits relative to females. Age-related abatement of social communication difficulties was observed for males but not females. Conversely, no sex differences were found for restricted/repetitive behaviours, which were stable over time for both males and females. The findings are discussed within the context of broader neurodevelopmental considerations that are common in NF1.

Electrophysiological and Behavioral Evidence for Hyper- and Hyposensitivity in Rare Genetic Syndromes Associated with Autism

Our study reviewed abnormalities in spontaneous, as well as event-related, brain activity in syndromes with a known genetic underpinning that are associated with autistic symptomatology. Based on behavioral and neurophysiological evidence, we tentatively subdivided the syndromes on primarily hyper-sensitive (Fragile X, Angelman) and hypo-sensitive (Phelan-McDermid, Rett, Tuberous Sclerosis, Neurofibromatosis 1), pointing to the way of segregation of heterogeneous idiopathic ASD, that includes both hyper-sensitive and hypo-sensitive individuals. This segmentation links abnormalities in different genes, such as FMR1, UBE3A, GABRB3, GABRA5, GABRG3, SHANK3, MECP2, TSC1, TSC2, and NF1, that are causative to the above-mentioned syndromes and associated with synaptic transmission and cell growth, as well as with translational and transcriptional regulation and with sensory sensitivity. Excitation/inhibition imbalance related to GABAergic signaling, and the interplay of tonic and phasic inhibition in different brain regions might underlie this relationship. However, more research is needed. As most genetic syndromes are very rare, future investigations in this field will benefit from multi-site collaboration with a common protocol for electrophysiological and event-related potential (EEG/ERP) research that should include an investigation into all modalities and stages of sensory processing, as well as potential biomarkers of GABAergic signaling (such as 40-Hz ASSR).

Social behavior in RASopathies and idiopathic autism

Background

RASopathies are genetic syndromes that result from pathogenic variants in the RAS-MAPK cellular signaling pathway. These syndromes, which include neurofibromatosis type 1, Noonan syndrome, cardiofaciocutaneous syndrome, and Costello syndrome, are associated with a complex array of medical and behavioral health complications. Despite a heightened risk for social challenges and autism spectrum disorder (ASD), few studies have compared different aspects of social behavior across these conditions. It is also unknown whether the underlying neuropsychological characteristics that contribute to social competence and socially empathetic (“prosocial”) behaviors differ in children with RASopathies as compared to children with nonsyndromic (i.e., idiopathic) ASD.

Methods

In this cross-sectional, survey-based investigation, caregivers of preschool and school-aged children with RASopathies (n = 202) or with idiopathic ASD (n = 109) provided demographic, medical, and developmental information about their child, including psychiatric comorbidities. For children who were able to communicate verbally, caregivers also completed standardized rating scales to assess social competence and empathetic behavior as well as symptoms of hyperactivity/inattention and emotional problems.

Results

As compared to children with idiopathic ASD, children with RASopathies were rated as demonstrating more resilience in the domain of empathy relative to their overall social competence. Similarities and differences emerged in the psychological factors that predicted social behavior in these two groups. Stronger communication skills and fewer hyperactive-impulsive behaviors were associated with increased empathy and social competence for both groups. Greater emotional challenges were associated with lower social competence for children with RASopathies and stronger empathy for children with idiopathic ASD. Among children with RASopathy and a co-occurring ASD diagnosis, socially empathetic behaviors were observed more often as compared to children with idiopathic ASD.

Conclusions

Findings suggest that the development of social behavior among children with RASopathies involves a distinct pattern of strengths and weaknesses as compared to a behaviorally defined disorder (idiopathic ASD). Identification of areas of resilience as well as behavioral and social challenges will support more targeted intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-021-09414-w.

Delineating the autistic phenotype in children with neurofibromatosis type 1

Background

Existing research has demonstrated elevated autistic behaviours in children with neurofibromatosis type 1 (NF1), but the autistic phenotype and its relationship to other neurodevelopmental manifestations of NF1 remains unclear. To address this gap, we performed detailed characterisation of autistic behaviours in children with NF1 and investigated their association with other common NF1 child characteristics.

Methods

Participants were drawn from a larger cross-sectional study examining autism in children with NF1. The population analysed in this study scored above threshold on the Social Responsiveness Scale-Second Edition (T-score ≥ 60; 51% larger cohort) and completed the Autism Diagnostic Interview-Revised (ADI-R) and/or the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2). All participants underwent evaluation of their intellectual function, and behavioural data were collected via parent questionnaires.

Results

The study cohort comprised 68 children (3–15 years). Sixty-three per cent met the ADOS-2 ‘autism spectrum’ cut-off, and 34% exceeded the more stringent threshold for ‘autistic disorder’ on the ADI-R. Social communication symptoms were common and wide-ranging, while restricted and repetitive behaviours (RRBs) were most commonly characterised by ‘insistence on sameness’ (IS) behaviours such as circumscribed interests and difficulties with minor changes. Autistic behaviours were weakly correlated with hyperactive/impulsive attention deficit hyperactivity disorder (ADHD) symptoms but not with inattentive ADHD or other behavioural characteristics. Language and verbal IQ were weakly related to social communication behaviours but not to RRBs.

Limitations

Lack of genetic validation of NF1, no clinical diagnosis of autism, and a retrospective assessment of autistic behaviours in early childhood.

Conclusions

Findings provide strong support for elevated autistic behaviours in children with NF1. While these behaviours were relatively independent of other NF1 comorbidities, the importance of taking broader child characteristics into consideration when interpreting data from autism-specific measures in this population is highlighted. Social communication deficits appear similar to those observed in idiopathic autism and are coupled with a unique RRB profile comprising prominent IS behaviours. This autistic phenotype and its relationship to common NF1 comorbidities such as anxiety and executive dysfunction will be important to examine in future research. Current findings have important implications for the early identification of autism in NF1 and clinical management.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00481-3.

Autism Symptoms in Children and Young Adults With Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis Complex, and Neurofibromatosis Type 1: A Cross-Syndrome Comparison

OBJECTIVE

The etiology of autism spectrum disorder (ASD) remains unclear, due to genetic heterogeneity and heterogeneity in symptoms across individuals. This study compares ASD symptomatology between monogenetic syndromes with a high ASD prevalence, in order to reveal syndrome specific vulnerabilities and to clarify how genetic variations affect ASD symptom presentation.

METHODS

We assessed ASD symptom severity in children and young adults (aged 0-28 years) with Fragile X Syndrome (FXS, n = 60), Angelman Syndrome (AS, n = 91), Neurofibromatosis Type 1 (NF1, n = 279) and Tuberous Sclerosis Complex (TSC, n = 110), using the Autism Diagnostic Observation Schedule and Social Responsiveness Scale. Assessments were part of routine clinical care at the ENCORE expertise center in Rotterdam, the Netherlands. First, we compared the syndrome groups on the ASD classification prevalence and ASD severity scores. Then, we compared individuals in our syndrome groups with an ASD classification to a non-syndromic ASD group (nsASD, n = 335), on both ASD severity scores and ASD symptom profiles. Severity scores were compared using MANCOVAs with IQ and gender as covariates.

RESULTS

Overall, ASD severity scores were highest for the FXS group and lowest for the NF1 group. Compared to nsASD, individuals with an ASD classification in our syndrome groups showed less problems on the instruments' social domains. We found a relative strength in the AS group on the social cognition, communication and motivation domains and a relative challenge in creativity; a relative strength of the NF1 group on the restricted interests and repetitive behavior scale; and a relative challenge in the FXS and TSC groups on the restricted interests and repetitive behavior domain.

CONCLUSION

The syndrome-specific strengths and challenges we found provide a frame of reference to evaluate an individual's symptoms relative to the larger syndromic population and to guide treatment decisions. Our findings support the need for personalized care and a dimensional, symptom-based diagnostic approach, in contrast to a dichotomous ASD diagnosis used as a prerequisite for access to healthcare services. Similarities in ASD symptom profiles between AS and FXS, and between NF1 and TSC may reflect similarities in their neurobiology. Deep phenotyping studies are required to link neurobiological markers to ASD symptomatology.

Assessing Psychiatric Comorbidity and Pharmacologic Treatment Patterns Among Patients With Neurofibromatosis Type 1

Background and objective

Neurofibromatosis 1 (NF1) is a genetic disorder that is accompanied by psychiatric comorbidities such as depression, anxiety, and attention-deficit hyperactivity disorder (ADHD) in more than half of the patients. However, there are limited data describing optimal treatment strategies for these conditions. This study aimed to address that gap in understanding and explore the neurobiological basis of psychiatric comorbidities in NF1.

Materials and methods

A retrospective cohort study was conducted among NF1 patients with a comorbid diagnosis of depression, anxiety, and/or ADHD. These disease states were chosen based on their relatively high reported prevalence in NF1 and shared pathophysiological mechanisms via monoaminergic dysfunction. Information regarding demographics, psychotherapeutic medication use, and clinical outcomes was gathered from electronic medical records. Relationships between patient- and medication-related factors and outcome measures were assessed using statistical analysis.

Results

The study population (n = 82) consisted of NF1 patients with a comorbid diagnosis of depression (76.8%), anxiety (53.7%), and/or ADHD (23.2%). The use of second-generation antipsychotic agent augmentation therapy or hydroxyzine monotherapy was associated with significantly more behavioral health (BH)-related emergency department (ED) visits, admissions, and inpatient days in the study population. Conversely, the use of bupropion augmentation therapy, buspirone augmentation therapy, and stimulants was associated with improved clinical outcomes, though these results were not statistically significant.

Conclusions

Based on our findings in this real-world study setting, patients with NF1 and psychiatric comorbidities appear to experience significant benefits from medications that enhance dopaminergic neurotransmission (e.g., bupropion, stimulants) when compared to drugs that oppose it (e.g., second-generation antipsychotics).

Translating the Role of mTOR- and RAS-Associated Signalopathies in Autism Spectrum Disorder: Models, Mechanisms and Treatment

Mutations affecting mTOR or RAS signaling underlie defined syndromes (the so-called mTORopathies and RASopathies) with high risk for Autism Spectrum Disorder (ASD). These syndromes show a broad variety of somatic phenotypes including cancers, skin abnormalities, heart disease and facial dysmorphisms. Less well studied are the neuropsychiatric symptoms such as ASD. Here, we assess the relevance of these signalopathies in ASD reviewing genetic, human cell model, rodent studies and clinical trials. We conclude that signalopathies have an increased liability for ASD and that, in particular, ASD individuals with dysmorphic features and intellectual disability (ID) have a higher chance for disruptive mutations in RAS- and mTOR-related genes. Studies on rodent and human cell models confirm aberrant neuronal development as the underlying pathology. Human studies further suggest that multiple hits are necessary to induce the respective phenotypes. Recent clinical trials do only report improvements for comorbid conditions such as epilepsy or cancer but not for behavioral aspects. Animal models show that treatment during early development can rescue behavioral phenotypes. Taken together, we suggest investigating the differential roles of mTOR and RAS signaling in both human and rodent models, and to test drug treatment both during and after neuronal development in the available model systems.

Atypical NF1 Microdeletions: Challenges and Opportunities for Genotype/Phenotype Correlations in Patients with Large NF1 Deletions

Patients with neurofibromatosis type 1 (NF1) and type 1 NF1 deletions often exhibit more severe clinical manifestations than patients with intragenic NF1 gene mutations, including facial dysmorphic features, overgrowth, severe global developmental delay, severe autistic symptoms and considerably reduced cognitive abilities, all of which are detectable from a very young age. Type 1 NF1 deletions encompass 1.4 Mb and are associated with the loss of 14 protein-coding genes, including NF1 and SUZ12. Atypical NF1 deletions, which do not encompass all 14 protein-coding genes located within the type 1 NF1 deletion region, have the potential to contribute to the delineation of the genotype/phenotype relationship in patients with NF1 microdeletions. Here, we review all atypical NF1 deletions reported to date as well as the clinical phenotype observed in the patients concerned. We compare these findings with those of a newly identified atypical NF1 deletion of 698 kb which, in addition to the NF1 gene, includes five genes located centromeric to NF1. The atypical NF1 deletion in this patient does not include the SUZ12 gene but does encompass CRLF3. Comparative analysis of such atypical NF1 deletions suggests that SUZ12 hemizygosity is likely to contribute significantly to the reduced cognitive abilities, severe global developmental delay and facial dysmorphisms observed in patients with type 1 NF1 deletions.

The mediating role of ADHD symptoms between executive function and social skills in children with neurofibromatosis type 1

Children with neurofibromatosis type 1 (NF1) often experience executive dysfunction, attention deficit/hyperactivity disorder (ADHD) symptoms and poor social skills, however, the nature of the relationships between these domains in children with NF1 is unclear. This study investigated these relationships using primary caregiver ratings of executive functions, ADHD symptoms and social skills in children with NF1. Participants were 136 children with NF1 and 93 typically developing (TD) controls aged 3-15 years recruited from 3 multidisciplinary neurofibromatosis clinics in Melbourne and Sydney, Australia, and Washington DC, USA. Mediation analysis was performed on primary outcome variables: parent ratings of executive functions (Behavior Rating Inventory of Executive Function, Metacognition Index), ADHD symptoms (Conners-3/Conners ADHD Diagnostic and Statistical Manual for Mental Disorders Scales) and social skills (Social Skills Improvement System-Rating Scale), adjusting for potential confounders (full scale IQ, sex, and social risk). Results revealed significantly poorer executive functions, elevated ADHD symptoms and reduced social skills in children with NF1 compared to controls. Poorer executive functions significantly predicted elevated ADHD symptoms and poorer social skills. Elevated ADHD symptoms significantly mediated the relationship between executive functions and social skills problems although did not fully account for social dysfunction. This study provides evidence for the importance of targeting ADHD symptoms as part of future interventions aimed at promoting prosocial behaviors in children with NF1.

Protein synthesis as a modifiable target for autism-related dendritic spine pathophysiologies

Autism spectrum disorder (ASD) is increasingly recognized as a condition of altered brain connectivity. As synapses are fundamental subcellular structures for neuronal connectivity, synaptic pathophysiology has become one of central themes in autism research. Reports disagree upon whether the density of dendritic spines, namely excitatory synapses, is increased or decreased in ASD and whether the protein synthesis that is critical for dendritic spine formation and function is upregulated or downregulated. Here, we review recent evidence supporting a subgroup of ASD models with decreased dendritic spine density (hereafter ASD-DSD), including Nf1 and Vcp mutant mice. We discuss the relevance of branched-chain amino acid (BCAA) insufficiency in relation to unmet protein synthesis demand in ASD-DSD. In contrast to ASD-DSD, ASD models with hyperactive mammalian target of rapamycin (mTOR) may represent the opposite end of the disease spectrum, often characterized by increases in protein synthesis and dendritic spine density (denoted ASD-ISD). Finally, we propose personalized dietary leucine as a strategy tailored to balancing protein synthesis demand, thereby ameliorating dendritic spine pathophysiologies and autism-related phenotypes in susceptible patients, especially those with ASD-DSD.

An executive functioning perspective in neurofibromatosis type 1: from ADHD and autism spectrum disorder to research domains

PURPOSE

Neurofibromatosis type 1 (NF1) is a rare monogenic disorder associated with executive function (EF) deficits and heightened risk for attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). The goal of this paper is to understand how EFs provide a common foundation to understand vulnerabilities for ADHD and ASD within NF1.

METHODS

A literature review and synthesis was conducted.

RESULTS

EF difficulties in working memory, inhibitory control, cognitive flexibility, and planning are evident in NF1, ADHD, and ASD. However, relatively little is known about the heterogeneity of EFs and ADHD and ASD outcomes in NF1. Assessment of ADHD and ASD in NF1 is based on behavioral symptoms without understanding neurobiological contributions. Recent efforts are promoting the use of dimensional and multidisciplinary methods to better understand normal and abnormal behavior, including integrating information from genetics to self-report measures.

CONCLUSION

NF1 is a monogenic disease with well-developed molecular and phenotypic research as well as complementary animal models. NF1 presents an excellent opportunity to advance our understanding of the neurobiological impact of known pathogenic variation in normal and abnormal neural pathways implicated in human psychopathology. EFs are core features of NF1, ADHD, and ASD, and these neurodevelopmental outcomes are highly prevalent in NF1. We propose a multilevel approach for understanding EFs in patients with NF1.This is essential to advance targeted interventions for NF1 patients and to advance the exciting field of research in this condition.

Genetic Counseling for Neurofibromatosis 1, Neurofibromatosis 2, and Schwannomatosis-Practice Resource of the National Society of Genetic Counselors

The goal of this practice resource is to provide genetic counselors and other healthcare professionals with a resource to reference when providing genetic counseling services to individuals and families undergoing evaluation for neurofibromatosis (NF) or who have received a diagnosis of NF, including NF1, NF2, and schwannomatosis. This resource represents the opinions of a multi-center working group of Certified Genetic Counselors with experience in the care of individuals with NF, providing topics to be considered for the incorporation into a clinical genetic counseling session.

Clinical characterization of children and adolescents with NF1 microdeletions

PURPOSE

An estimated 5-11% of patients with neurofibromatosis type 1 (NF1) harbour NF1 microdeletions encompassing the NF1 gene and its flanking regions. The purpose of this study was to evaluate the clinical phenotype in children and adolescents with NF1 microdeletions.

METHODS

We retrospectively analysed 30 children and adolescents with NF1 microdeletions pertaining to externally visible neurofibromas. The internal tumour load was determined by volumetry of whole-body magnetic resonance imaging (MRI) in 20 children and adolescents with NF1 microdeletions. Furthermore, the prevalence of global developmental delay, autism spectrum disorder and attention deficit hyperactivity disorder (ADHD) were evaluated.

RESULTS

Children and adolescents with NF1 microdeletions had significantly more often cutaneous, subcutaneous and externally visible plexiform neurofibromas than age-matched patients with intragenic NF1 mutations. Internal neurofibromas were detected in all 20 children and adolescents with NF1 microdeletions analysed by whole-body MRI. By contrast, only 17 (61%) of 28 age-matched NF1 patients without microdeletions had internal tumours. The total internal tumour load was significantly higher in NF1 microdeletion patients than in NF1 patients without microdeletions. Global developmental delay was observed in 28 (93%) of 30 children with NF1 microdeletions investigated. The mean full-scale intelligence quotient in our patient group was 77.7 which is significantly lower than that of patients with intragenic NF1 mutations. ADHD was diagnosed in 15 (88%) of 17 children and adolescents with NF1 microdeletion. Furthermore, 17 (71%) of the 24 patients investigated had T-scores ≥ 60 up to 75, indicative of mild to moderate autistic symptoms, which are consequently significantly more frequent in patients with NF1 microdeletions than in the general NF1 population. Also, the mean total T-score was significantly higher in patients with NF1 microdeletions than in the general NF1 population.

CONCLUSION

Our findings indicate that already at a very young age, NF1 microdeletions patients frequently exhibit a severe disease manifestation which requires specialized long-term clinical care.

The Neurofibromatoses

BACKGROUND

Neurofibromatosis of types 1 and 2 (NF1, NF2) and schwannomatosis are the diseases that make up the neurofibromatosis spectrum. With respective incidences of 1 in 3000, 1 in 33 000, and 1 in 60 000 births, they form part of the group of rare tumor-suppressor syndromes. They give rise to a greater tumor burden for the nervous system than any other type of neoplastic disease. New approaches to symptomatic treatment are emerging.

METHODS

This review is based on articles retrieved by a selective literature search on the pathogenesis, diagnosis, and treatment of the neurofibromatoses.

RESULTS

NF1 and NF2 are monogenic diseases, while the genetics of schwannomatosis is complex. The three entities are clinically and pathophysiologically distinct. An important aspect of their tumor biology is the alternation of growth phases and growth pauses. Correlations between genotypes and phenotypes are variable, while new mutations and genetic mosaics are common. Ninety-nine percent of patients with NF1 have six or more café-au-lait spots by the age of 12 months; 90-95% of patients with NF2 develop bilateral vestibular schwannomas. In schwannomatosis, pain is the most prominent symptom; two-thirds of those affected develop spinal schwannomas. The severity and prognosis of these disorders are not closely correlated with the radiological findings; rather, neurologic deficits, malignant transformation, and psychosocial stress are of greater clinical importance. Advances in knowledge of pathophysiology have led to the development of targeted treatment approaches. Examples include the off-label treatment of vestibular schwannomas with bevacizumab and of plexiform neurofibromas with MEK inhibitors.

CONCLUSION

Patients with neurofibromatoses need individualized care. They should be treated in centers of expertise where interdisciplinary consultation is available and new types of pharmacotherapy can be provided.

The TAND checklist: a useful screening tool in children with tuberous sclerosis and neurofibromatosis type 1

BACKGROUND

Tuberous Sclerosis Complex (TSC) and Neurofibromatosis type 1 (NF1) are neurocutaneous disorders commonly characterized by neuropsychiatric comorbidities. The TAND (Tuberous Sclerosis Associated Neuropsychiatric Disorders) Checklist is currently used to quickly screen for behavioural, psychiatric, intellectual, academic, neuropsychological and psychosocial manifestations in patients with TSC. We administered the authorized Italian version of the TAND Checklist to the parents of 42 TSC patients and 42 age- and sex-matched NF1 patients, for a total of 84 individuals, aged 4-20 years. Aims of this study: - to test the overall usability of the TAND Checklist in NF1, -to compare the results between children and adolescents with TSC and NF1, and -to examine the association between neuropsychiatric manifestations and severity of the phenotype in terms of epilepsy severity in the TSC cohort and disease severity according to the modified version of the Riccardi severity scale in the NF1 cohort.

RESULTS

TSC cohort: 35.6% had Intellectual Disability (ID), 11.9% Specific Learning Disorders (SLD), 50.0% Attention Deficit Hyperactivity Disorder (ADHD) and 16.6% anxious/mood disorder. 33.3% had a formal diagnosis of Autism Spectrum Disorder (ASD). Paying attention and concentrating (61.9%), impulsivity (54.8%), temper tantrums (54.8%), anxiety (45.2%), overactivity/hyperactivity (40.5%), aggressive outburst (40.5%), absent or delayed onset of language (40.5%), repetitive behaviors (35.7%), academic difficulties (> 40%), deficits in attention (61.9%) and executive skills (50.0%) were the most commonly reported problems. NF1 cohort: 9.5% had ID, 21.4% SLD, 46.6% ADHD, and 33.3% anxious/mood disorder. No one had a diagnosis of ASD. Commonly reported issues were paying attention and concentrating (59.5%), impulsivity (52.4%), anxiety (50.0%), overactivity/hyperactivity (38.1%), temper tantrums (38.1%), academic difficulties (> 40%), deficits in attention (59.5%), and executive skills (38.1%). Neuropsychiatric features in TSC vs NF1: Aggressive outburst and ASD features were reported significantly more frequently in TSC than in NF1. Neuropsychiatric manifestations and phenotype severity: Depressed mood, absent or delayed onset of language, repetitive language, difficulties in relationship with peers, repetitive behaviors, spelling, mathematics, dual-tasking, visuo-spatial tasks, executive skills, and getting disoriented were significantly different among TSC patients with different epilepsy severity. No statistically significant differences in the NF1 subgroups were noted for any of the items in the checklist.

CONCLUSION

The TAND Checklist used for TSC is acceptable and feasible to complete in a clinical setting, and is able to detect the complexity of neuropsychiatric involvement in NF1 as well. NF1 is mainly characterized by an ADHD profile, anxiety problems and SLD, while ASD features are strongly associated with TSC. In conclusion, the TAND Checklist is a useful and feasible screening tool, in both TSC and NF1.

Developmental loss of neurofibromin across distributed neuronal circuits drives excessive grooming in Drosophila

Neurofibromatosis type 1 is a monogenetic disorder that predisposes individuals to tumor formation and cognitive and behavioral symptoms. The neuronal circuitry and developmental events underlying these neurological symptoms are unknown. To better understand how mutations of the underlying gene (NF1) drive behavioral alterations, we have examined grooming in the Drosophila neurofibromatosis 1 model. Mutations of the fly NF1 ortholog drive excessive grooming, and increased grooming was observed in adults when Nf1 was knocked down during development. Furthermore, intact Nf1 Ras GAP-related domain signaling was required to maintain normal grooming. The requirement for Nf1 was distributed across neuronal circuits, which were additive when targeted in parallel, rather than mapping to discrete microcircuits. Overall, these data suggest that broadly-distributed alterations in neuronal function during development, requiring intact Ras signaling, drive key Nf1-mediated behavioral alterations. Thus, global developmental alterations in brain circuits/systems function may contribute to behavioral phenotypes in neurofibromatosis type 1.

Examination of the genetic factors underlying the cognitive variability associated with neurofibromatosis type 1

Purpose

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder associated with cognitive deficits. The NF1 cognitive phenotype is generally considered to be highly variable, possibly due to the observed T2-weighted hyperintensities, loss of heterozygosity, NF1-specific genetic modifiers, or allelic imbalance.

Methods

We investigated cognitive variability and assessed the contribution of genetic factors by performing a retrospective cohort study and a monozygotic twin case series. We included data of 497 children with genetically confirmed NF1 and an IQ assessment, including 12 monozygotic twin and 17 sibling sets.

Results

Individuals carrying an NF1 chromosomal microdeletion showed significant lower full-scale IQ (FSIQ) scores than individuals carrying intragenic pathogenic NF1 variants. For the intragenic subgroup, the variability in cognitive ability and the correlation of IQ between monozygotic NF1 twin pairs or between NF1 siblings is similar to the general population.

Conclusions

The variance and heritability of IQ in individuals with NF1 are similar to that of the general population, and hence mostly driven by genetic background differences. The only factor that significantly attenuates IQ in NF1 individuals is the NF1 chromosomal microdeletion genotype. Implications for clinical management are that individuals with intragenic NF1 variants that score <1.5–2 SD below the mean of the NF1 population should be screened for additional causes of cognitive disability.

Autism Spectrum Disorder Symptom Profile Across the RASopathies

Dysregulation of the Ras MAPK signaling pathway is implicated in the pathogenesis of autism spectrum disorder (ASD). The RASopathies, a group of disorders caused by mutations of the Ras/MAPK pathway genes, share many overlapping clinical features. Studies suggest a high prevalence of ASD in the RASopathies, but detailed characterization of the ASD profile is lacking. The aim of this study was to compare the ASD symptom profile of three distinct RASopathies associated with both gain-of-function and loss-of-function mutations: neurofibromatosis type 1 (NF1), Noonan syndrome (NS), and cardiofaciocutaneous syndrome (CFC). Participants were drawn from existing databases if they had a diagnosis of a RASopathy, met the criteria for ASD, and were able to communicate verbally. We compared the phenotypic profile of NF1 + ASD (n = 48), NS + ASD (n = 11), and CFC + ASD (n = 7) on the Autism Diagnostic Inventory (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS). We found subtle but non-significant group differences with higher levels of social impairments and lower restricted repetitive behaviors in the NF1 group as compared with the NS and CFC groups. We observed group differences in developmental milestones with most severe delays in CFC, followed by NS and NF1. Our results suggest that despite developmental differences, the ASD profile remains relatively consistent across the three RASopathies. Though our results need confirmation in larger samples, they suggest the possibility that treatment and mechanistic insights developed in the context of one RASopathy may be generalizable to others and possibly to non-syndromic ASD associated with dysregulation of Ras/MAPK pathway genes.

Autism needs to be considered in children with Down Syndrome

AIM

To analyse levels and profiles of autism symptoms in children with Down Syndrome (DS) with and without diagnosed autism spectrum disorder (ASD) and to specifically study the groups with severe Intellectual Disability (ID).

METHODS

From a population-based cohort of 60 children with DS (age 5-17 years) with 41 participating children, scores obtained from the Autism Diagnostic Observation Schedule (ADOS) Module-1 algorithm were compared between those with and without diagnosed ASD. Children with DS and ASD were also compared to a cohort of children with idiopathic ASD, presented in the ADOS manual.

RESULTS

Children with DS and ASD had significantly higher ADOS scores in all domains compared to those without ASD. When the groups with DS, with and without ASD, were restricted to those with severe ID, the difference remained. When the children with DS and ASD and the idiopathic autism group were compared, the ADOS profiles were similar.

CONCLUSION

A considerable proportion of children with DS has ASD, but there is also a group of children with DS and severe ID without autism. There is a need to increase awareness of the high prevalence of autism in children with DS to ensure that appropriate measures and care are provided.

Emotional functioning among children with neurofibromatosis type 1 or Noonan syndrome

While neurofibromatosis type 1 (NF1) and Noonan syndrome (NS) are clinically distinct genetic syndromes, they have overlapping features because they are caused by pathogenic variants in genes encoding molecules within the Ras-mitogen-activated protein kinase signaling pathway. Increased risk for emotional and behavioral challenges has been reported in both children and adults with these syndromes. The current study examined parent-report and self-report measures of emotional functioning among children with NF1 and NS as compared to their unaffected siblings. Parents and children with NS (n = 39), NF1 (n = 39), and their siblings without a genetic condition (n = 32) completed well-validated clinical symptom rating scales. Results from parent questionnaires indicated greater symptomatology on scales measuring internalizing behaviors and symptoms of attention deficit hyperactivity disorder (ADHD) in both syndrome groups as compared with unaffected children. Frequency and severity of emotional and behavioral symptoms were remarkably similar across the two clinical groups. Symptoms of depression and anxiety were higher in children who were also rated as meeting symptom criteria for ADHD. While self-report ratings by children generally correlated with parent ratings, symptom severity was less pronounced. Among unaffected siblings, parent ratings indicated higher than expected levels of anxiety. Study findings may assist with guiding family-based interventions to address emotional challenges.

Understanding autism spectrum disorder and social functioning in children with neurofibromatosis type 1: protocol for a cross-sectional multimodal study

INTRODUCTION

Children with the single-gene disorder neurofibromatosis type 1 (NF1) appear to be at an increased risk for autism spectrum disorder (ASD) and exhibit a unique social-cognitive phenotype compared with children with idiopathic ASD. A complete framework is required to better understand autism in NF1, from neurobiological levels through to behavioural and functional outcomes. The primary aims of this study are to establish the frequency of ASD in children with NF1, examine the social cognitive phenotype, investigate the neuropsychological processes contributing to ASD symptoms and poor social functioning in children with NF1, and to investigate novel structural and functional neurobiological markers of ASD and social dysfunction in NF1. The secondary aim of this study is to compare the neuropsychological and neurobiological features of ASD in children with NF1 to a matched group of patients with idiopathic ASD.

METHODS AND ANALYSIS

This is an international, multisite, prospective, cross-sectional cohort study of children with NF1, idiopathic ASD and typically developing (TD) controls. Participants will be 200 children with NF1 (3-15 years of age), 70 TD participants (3-15 years) and 35 children with idiopathic ASD (7-15 years). Idiopathic ASD and NF1 cases will be matched on age, sex and intelligence. All participants will complete cognitive testing and parents will rate their child's behaviour on standardised questionnaires. Neuroimaging will be completed by a subset of participants aged 7 years and older. Children with NF1 that screen at risk for ASD on the parent-rated Social Responsiveness Scale 2nd Edition will be invited back to complete the Autism Diagnostic Observation Scale 2nd Edition and Autism Diagnostic Interview-Revised to determine whether they fulfil ASD diagnostic criteria.

ETHICS AND DISSEMINATION

This study has hospital ethics approval and the results will be disseminated through peer-reviewed publications and international conferences.

Measurement considerations in pediatric research on autism spectrum disorders

Studying Autism Spectrum Disorders (ASD) in genetic syndromes has gained interest in the scientific community as a way to elucidate mechanisms and symptom profiles to understand ASD more broadly. Appropriate and adequate measurement of constructs, symptomatology, and outcomes in clinical research is of vital importance in establishing the prevalence of such symptoms and measuring change in symptoms in the context of clinical trials. As such, we provide an overview of the prevalence of ASD, present current diagnostic guidelines, discuss important comorbidities to consider, describe current assessment strategies in assessing ASD, and discuss these within the context of a specific genetic condition to highlight how ASD can be best evaluated.

Social skills in children with RASopathies: a comparison of Noonan syndrome and neurofibromatosis type 1

Background

Gene mutations within the RAS-MAPK signaling cascade result in Noonan syndrome (NS), neurofibromatosis type 1 (NF1), and related disorders. Recent research has documented an increased risk for social difficulties and features of autism spectrum disorder (ASD) among children with these conditions. Despite this emerging evidence, the neuropsychological characteristics associated with social skills deficits are not well understood, particularly for children with NS.

Methods

Parents of children with NS (n = 39), NF1 (n = 39), and unaffected siblings (n = 32) between the ages of 8 and 16 years were administered well-validated caregiver questionnaires assessing their child’s social skills, language abilities, attention-deficit hyperactivity disorder (ADHD) symptoms and anxiety.

Results

With respect to overall social skills, average ratings of children in both clinical groups were similar, and indicated weaker social skills compared to unaffected siblings. Although ratings of social skills were outside of normal limits for more than four in ten children within the clinical groups, most of the deficits were mild/moderate. Fifteen percent of the children with NS and 5% of the children with NF1 were rated as having severe social skills impairment (< − 2SD). Independent of diagnosis, having fewer ADHD symptoms or better social-pragmatic language skills was predictive of stronger social skills.

Conclusions

Amidst efforts to support social skill development among children and adolescents with RASopathies, neuropsychological correlates such as social language competence, attention, and behavioral self-regulation could be important targets of intervention.