This study examines the course of intelligence in children with neurofibromatosis type 1 (NF1) and factors influencing changes. In this cross-sectional and longitudinal study, 397 children were assessed at ages 3, 6, 11, and 15 years using a neuropsychological test battery. Comparisons of demographics and scores were conducted across and within cross-sectional and longitudinal groups. Cross-sectionally, 15-year-olds outperformed 11-year-olds on Performance IQ (PIQ). A reduced PIQ at age 11 years was found that appeared to recover by age 15 years in the longitudinal group. The mother's level of education, the mode of inheritance, or attention-deficit hyperactivity disorder were not predictive of these changes. Overall, intelligence remains stable in children with NF1 between 3 and 15 years of age. The gap between PIQ and VIQ decreases over time. Neurocognitive monitoring is recommended during the critical period between ages 6 and 11 years due to risks of attention and learning issues.

Objective Children with the autosomal dominant disorder Neurofibromatosis 1 (NF1) exhibit a high prevalence of both attention-deficit/hyperactivity disorder (ADHD) (up to 40%) and autism (up to 11%). The genetic mechanisms underlying these behavioral phenotypes are largely unexplored. This study examines the associations between various NF1 genotypes and NF1 behavioral phenotypes. Method A retrospective cohort study was carried out in children and adolescents with NF1 from three national referral centers for NF1 (the Netherlands, the UK and Belgium). Anonymized data was collected on five primary outcomes to characterize the behavioral phenotype in NF1: autistic traits (Social Responsiveness Scale 2 [SRS-2] Total T-score and Autism Diagnostic Observation Schedule [ADOS] Calibrated Severity Score); attention-deficit/hyperactivity disorder characteristics (Conners Inattention and Hyperactivity T-score) and global behavioral/emotional problems (Child Behavior Checklist [CBCL] Total Problems T-score). Genotypes were categorized based on three types of NF1 variant definitions: (1) coding variant type, (2) variant effect (truncating vs. non-truncating variants), and (3) the location within the gene. Results In total, 408 children and adolescents with NF1 were included, of which 187 (46%) were female. Range of median age at assessment across all outcomes was 6.0-8.4 years. Behavioral outcomes were not associated to any of the NF1 genotypes categories examined. Conclusion In this large cohort, autism traits, ADHD characteristics or global behavioral/emotional problems were not associated with NF1 variant type, effect or location. These findings indicate that the NF1 variant classes examined here do not differentially influence the NF1 behavioral phenotype, although genotype–phenotype associations at the single codon level cannot be ruled out.

Background Current paediatric neuroradiology relies largely on visual inspection and semiquantitative scoring, limiting detection of subtle abnormalities in the developing brain. The present study aimed to develop population-based neuroimaging growth curves for clinical use to assess paediatric neurodevelopmental trajectories and identify deviations from typical brain maturation. Methods The study was conducted within the Generation R Study, a prospective, population-based birth cohort study based in Rotterdam, the Netherlands. A neuroimaging substudy consisted of four neuroimaging waves: 6·1–10·7 years (2010–13), 8·6–12·0 years (2013–15), 12·5–17·1 years (2016–20), and 16·2–20·4 years (2022–23). To assess clinical applicability, percentile curves were calculated for three clinical cohorts. Exclusion criteria included general contraindications for MRI, severe neurological disorders, significant incidental findings, and incomplete or poor-quality scans. Brain volumes were measured using FreeSurfer, whereas microstructural markers, fractional anisotropy, and mean diffusivity, were processed using FMRIB Software Library. Sex-specific neuroimaging growth curves were constructed using quantile regression analyses. Participants were stratified by European and non-European backgrounds. Findings 7316 brain MRI scans from 4551 participants (3587 [49·0%] males, 3729 [51·0%] females) were analysed: 6·1–10·7 years (n=921), 8·6–12·0 years (n=3135), 12·5–17·1 years (n=2118), and 16·2–20·4 years (n=1142). Clinical cohorts included individuals with very preterm birth (VPB; n=32), multiple sclerosis (MS; n=27), and sickle cell disease (SCD; n=18). Total brain volume followed an inverted U-shaped trajectory, peaking at 13–15 years, with subsequent decline attributable mainly to grey matter reduction, while white matter volume increased until late adolescence. Cortical and deep grey matter volumes showed nonlinear developmental patterns, characterised by early increases that reached region-specific peaks. Regional patterns were consistent with these trends, with slightly larger volumes observed in males than in females. Microstructural markers showed increasing fractional anisotropy and decreasing mean diffusivity with age. Clinical cohorts showed notable deviations from normative curves. Interpretation The developed growth curves provide a quantitative reference framework for paediatric brain development and identify subtle but clinically relevant deviations in specific patient groups, and have the potential to enhance diagnostic accuracy, advance understanding of pathophysiological mechanisms, and guide therapeutic strategies. Funding Erasmus Medical Center; Erasmus University Rotterdam; the Netherlands Organization for Health Research and Development (ZonMw); the Netherlands Organization for Scientific Research (NWO); the Ministry of Health, Welfare and Sport; Hartstichting; Intramural Research Program of the National Institute of Mental Health.

BACKGROUND:Epilepsy is a core feature of Angelman syndrome (AS) and a major contributor to morbidity and caregiver burden. The current study provides updated caregiver-reported data on seizure characteristics, triggers, and management in AS. METHODS:Caregivers of 130 individuals with AS enrolled in the Linking Angelman and Dup15q Data for Expanded Research Database completed an online questionnaire assessing seizure characteristics, age at first seizure and diagnosis, perceived triggers, and management strategies. Participants were grouped by molecular subtype (deletion vs nondeletion). Descriptive statistics and group comparisons were conducted. RESULTS:Seizures were more frequently reported in individuals with deletion subtypes compared to those with nondeletion subtypes. The most common seizure-related manifestations (myoclonic, atonic, and atypical absence features) did not differ between groups. Individuals with deletion subtypes experienced earlier epilepsy diagnosis than those with nondeletion subtypes, though age at first seizure prompting medical attention did not differ significantly between the groups. About half of caregivers were unsure of seizure triggers; among identified triggers, illness or infection with a fever was most common. Pharmacologic treatment was the primary management approach, with levetiracetam most frequently reported. Side effects were the most common reason for medication discontinuation, and only 69% of caregivers reported access to or use of an acute seizure rescue medication. CONCLUSIONS:Caregiver-reported data from the Linking Angelman and Dup15q Data for Expanded Research Database provide an updated characterization of seizures in AS. Gaps in trigger identification and availability or use of rescue medications highlight opportunities to improve standard-of-care implementation in AS.

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.

Angelman syndrome (AS) is a rare neurogenetic disorder. Previous studies indicate a high prevalence of autism spectrum disorder (ASD) with considerable variability. Little is known regarding the longitudinal trajectory of autistic traits. We aim to investigate autistic traits, the effect of age on these traits, and associated features in AS children. This (partly) longitudinal clinical record study at the ENCORE Expertise Center involved 107 AS children aged 2-18 with one (N = 107), two (N = 49), or three (N = 14) measurements. Autistic traits and sensory processing issues were assessed using various instruments, and DSM classifications were used descriptively. Covariates were genotype, gender, and epilepsy. Results indicate a high prevalence of autistic traits and sensory processing issues. Children with the deletion genotype exhibited more autistic traits. Autism Diagnostic Observation Schedule (ADOS) classifications indicated higher rates of ASD compared to clinician DSM classifications. Autistic traits generally remained stable over time, except that ADOS scores significantly decreased for children with the UBE3A mutation genotype, and in the social affect domain for the entire group. In conclusion, incorporating the assessment of autistic traits and sensory processing into clinical practice for AS is important to inform adaptations of the environment to meet the child's needs. Additionally, clinicians and researchers should be mindful of the potential for overestimating ASD traits in AS when relying on the ADOS. ASD diagnosis in AS should integrate multiple diagnostic instruments, diverse hetero-anamnestic sources, and multidisciplinary expert opinions.

Predicting and quantifying phenotypic consequences of genetic variants in rare disorders is a major challenge, particularly pertinent for ‘actionable’ genes such as thyroid hormone transporter MCT8 (encoded by the X-linked SLC16A2 gene), where loss-of-function (LoF) variants cause a rare neurodevelopmental and (treatable) metabolic disorder in males. The combination of deep phenotyping data with functional and computational tests and with outcomes in population cohorts, enabled us to: (i) identify the genetic aetiology of divergent clinical phenotypes of MCT8 deficiency with genotype-phenotype relationships present across survival and 24 out of 32 disease features; (ii) demonstrate a mild phenocopy in ~400,000 individuals with common genetic variants in MCT8; (iii) assess therapeutic effectiveness, which did not differ among LoF-categories; (iv) advance structural insights in normal and mutated MCT8 by delineating seven critical functional domains; (v) create a pathogenicity-severity MCT8 variant classifier that accurately predicted pathogenicity (AUC:0.91) and severity (AUC:0.86) for 8151 variants. Our information-dense mapping provides a generalizable approach to advance multiple dimensions of rare genetic disorders.

Angelman syndrome (AS) is a rare genetic neurodevelopmental disorder with intellectual disability, limited to no speech development, epilepsy, motor deficits, and behavioral issues. Children with AS generally demonstrate better language comprehension than expressive language skills, but language comprehension is difficult to measure since commonly used tests rely on fine motor skills and/or require a certain level of intellectual functioning. The Computer-Based instrument for Low motor Language Testing (C-BiLLT) was developed to assess language comprehension in non-speaking children with motor impairments. This study assessed the feasibility, construct validity and sensitivity of the C-BiLLT in a clinical cohort of 65 children with AS (2 to 19 years old). All participants successfully finished the test, without floor or ceiling effects. The C-BiLLT showed good construct validity, reflected by a significant correlation with the Bayley language comprehension subscale and with related constructs (expressive language measured by the Communication Matrix and the Bayley cognition subscale). C-BiLLT scores were associated with age. Finally, the C-BiLLT was sensitive to differentiate between AS genotypes. In conclusion, we demonstrate that the C-BiLLT is a feasible, valid and sensitive measurement instrument for language comprehension in children with AS. We recommend using the C-BiLLT in clinical practice and in scientific research.

Pathogenic variants resulting in protein phosphatase 2A (PP2A) dysfunction result in mild to severe neurodevelopmental delay. PP2A is a trimer of a catalytic (C) subunit, scaffolding (A) subunit, and substrate binding/regulatory (B) subunit, encoded by 19 different genes. De novo missense variants in PPP2R5D (B56δ) or PPP2R1A (Aα) and de novo missense and loss-of-function variants in PPP2CA (Cα) lead to syndromes with overlapping phenotypic features, known as Houge-Janssens syndrome (HJS) types 1, 2, and 3, respectively. Here, we describe an additional condition in the HJS spectrum in 26 individuals with variants in PPP2R5C, encoding the regulatory B56γ subunit. Most changes were de novo and of the missense type. The clinical features were well within the HJS spectrum with strongest resemblance to HJS type 1, caused by B56δ variants. Common features were neurodevelopmental delay and hypotonia, with a high risk of epilepsy, behavioral problems, and mildly dysmorphic facial features. Head circumferences were above average or macrocephalic. The degree of intellectual disability was, on average, milder than in other HJS types. All variants affected either substrate binding (2/19), C-subunit binding (2/19), or both (15/19). Five variants were recurrent. Catalytic activity of the phosphatase was variably affected by the variants. Of note, PPP2R5C total loss-of-function variants could be inherited from a non-symptomatic parent. This implies that a dominant-negative mechanism on substrate dephosphorylation or general PP2A function is the most likely pathogenic mechanism.

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.

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.

BACKGROUND AND OBJECTIVES:Knowledge of young-onset Alzheimer disease in adults with Down syndrome has greatly improved clinical care. However, little is known about dementia in rare genetic neurodevelopmental disorders (RGNDs). In this review, a comprehensive overview is provided of reports on dementia and cognitive/adaptive trajectories in adults with RGNDs. METHODS:A systematic literature review was conducted in Embase, Medline ALL, and PsycINFO on December 6, 2022. The protocol was registered in PROSPERO (CRD42021223041). Search terms for dementia, cognitive and adaptive functioning, and RGNDs were combined using generic terms and the Orphanet database. Study characteristics and descriptive data on genetic diagnosis, clinical and neuropathologic features, comorbidities, and diagnostic methods were extracted using a modified version of the Cochrane Data Extraction Template. RESULTS:The literature search yielded 40 publications (17 cohorts, 23 case studies) describing dementia and/or cognitive or adaptive trajectories in adults with 14 different RGNDs. Dementia was reported in 49 individuals (5 cohorts, 20 cases) with a mean age at onset of 44.4 years. Diagnostics were not disclosed for half of the reported individuals (n = 25/49, 51.0%). A total of 44 different psychodiagnostic instruments were used. MRI was the most reported additional investigation (n = 12/49, 24.5%). Comorbid disorders most frequently associated with cognitive/adaptive decline were epilepsy, psychotic disorders, and movement disorders. DISCUSSION:Currently available literature shows limited information on aging in RGNDs, with relatively many reports of young-onset dementia. Longitudinal data may provide insights into converging neurodevelopmental degenerative pathways. We provide recommendations to optimize dementia screening, diagnosis, and research.

Background Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by severe intellectual disability, little to no expressive speech, visual and motor problems, emotional/behavioral challenges, and a tendency towards hyperphagia and weight gain. The characteristics of AS make it difficult to measure these children’s functioning with standard clinical tests. Feasible outcome measures are needed to measure current functioning and change over time, in clinical practice and clinical trials. Aim Our first aim is to assess the feasibility of several functional tests. We target domains of neurocognitive functioning and physical growth using the following measurement methods: eye-tracking, functional Near-Infrared Spectroscopy (fNIRS), indirect calorimetry, bio-impedance analysis (BIA), and BOD POD (air-displacement plethysmography). Our second aim is to explore the results of the above measures, in order to better understand the AS phenotype. Methods The study sample consisted of 28 children with AS aged 2–18 years. We defined an outcome measure as feasible when (1) at least 70% of participants successfully finished the measurement and (2) at least 60% of those participants had acceptable data quality. Adaptations to the test procedure and reasons for early termination were noted. Parents rated acceptability and importance and were invited to make recommendations to increase feasibility. The results of the measures were explored. Results Outcome measures obtained with eye-tracking and BOD POD met the definition of feasibility, while fNIRS, indirect calorimetry, and BIA did not. The most important reasons for early termination of measurements were showing signs of protest, inability to sit still and poor/no calibration (eye-tracking specific). Post-calibration was often applied to obtain valid eye-tracking results. Parents rated the BOD POD als most acceptable and fNIRS as least acceptable for their child. All outcome measures were rated to be important. Exploratory results indicated longer reaction times to high salient visual stimuli (eye-tracking) as well as high body fat percentage (BOD POD). Conclusions Eye-tracking and BOD POD are feasible measurement methods for children with AS. Eye-tracking was successfully used to assess visual orienting functions in the current study and (with some practical adaptations) can potentially be used to assess other outcomes as well. BOD POD was successfully used to examine body composition. Trial registration Registered d.d. 23-04-2020 under number ‘NL8550’ in the Dutch Trial Register: https://onderzoekmetmensen.nl/en/trial/23075

Background and ObjectivesKnowledge of young-onset Alzheimer disease in adults with Down syndrome has greatly improved clinical care. However, little is known about dementia in rare genetic neurodevelopmental disorders (RGNDs). In this review, a comprehensive overview is provided of reports on dementia and cognitive/adaptive trajectories in adults with RGNDs.MethodsA systematic literature review was conducted in Embase, Medline ALL, and PsycINFO on December 6, 2022. The protocol was registered in PROSPERO (CRD42021223041). Search terms for dementia, cognitive and adaptive functioning, and RGNDs were combined using generic terms and the Orphanet database. Study characteristics and descriptive data on genetic diagnosis, clinical and neuropathologic features, comorbidities, and diagnostic methods were extracted using a modified version of the Cochrane Data Extraction Template.ResultsThe literature search yielded 40 publications (17 cohorts, 23 case studies) describing dementia and/or cognitive or adaptive trajectories in adults with 14 different RGNDs. Dementia was reported in 49 individuals (5 cohorts, 20 cases) with a mean age at onset of 44.4 years. Diagnostics were not disclosed for half of the reported individuals (n = 25/49, 51.0%). A total of 44 different psychodiagnostic instruments were used. MRI was the most reported additional investigation (n = 12/49, 24.5%). Comorbid disorders most frequently associated with cognitive/adaptive decline were epilepsy, psychotic disorders, and movement disorders.DiscussionCurrently available literature shows limited information on aging in RGNDs, with relatively many reports of young-onset dementia. Longitudinal data may provide insights into converging neurodevelopmental degenerative pathways. We provide recommendations to optimize dementia screening, diagnosis, and research.

BACKGROUND:The aim of this study was to determine treatment response and whether it is associated with antibody titre change in patients with autoimmune nodopathy (AN) previously diagnosed as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and to compare clinical features and treatment response between AN and CIDP. METHODS:Serum IgG antibodies to neurofascin-155 (NF155), contactin-1 (CNTN1) and contactin-associated protein 1 (CASPR1) were detected with cell-based assays in patients diagnosed with CIDP. Clinical improvement was determined using the modified Rankin scale, need for alternative and/or additional treatments and assessment of the treating neurologist. RESULTS:We studied 401 patients diagnosed with CIDP and identified 21 patients with AN (10 anti-NF155, 6 anti-CNTN1, 4 anti-CASPR1 and 1 anti-NF155/anti-CASPR1 double positive). In patients with AN ataxia (68% vs 28%, p=0.001), cranial nerve involvement (34% vs 11%, p=0.012) and autonomic symptoms (47% vs 22%, p=0.025) were more frequently reported; patients with AN improved less often after intravenous immunoglobulin treatment (39% vs 80%, p=0.002) and required additional/alternative treatments more frequently (84% vs 34%, p<0.001), compared with patients with CIDP. Antibody titres decreased or became negative in patients improving on treatment. Treatment withdrawal was associated with a titre increase and clinical deterioration in four patients. CONCLUSIONS:Distinguishing CIDP from AN is important, as patients with AN need a different treatment approach. Improvement and relapses were associated with changes in antibody titres, supporting the pathogenicity of these antibodies.

Background: Guillain-Barre ' syndrome (GBS) has a highly variable clinical course and outcome as indicated by the risk of developing respiratory failure and residual inability to walk. Prognostic models as Erasmus GBS Respi-ratory Insufficiency Score (EGRIS) developed in adult patients are inaccurate in children. Our aim was to determine the prognostic factors of respiratory failure and inability to walk in children with GBS and to develop a new clinical prognostic model for individual patients (EGRIS-Kids).Methods: A multicenter retrospective cohort study was performed using the data of children (younger than 18 years) fulfilling the diagnostic criteria for GBS from the NINDS. This study was performed in two independent cohorts from centers in Germany, Switzerland, Austria (N = 265, collected 1989-2002) and The Netherlands (N = 156, collected 1987-2016). The predicted main outcomes were occurrence of respiratory failure during the disease course and inability to walk independent at one year after diagnosis. Results: In the combined cohort of 421 children, 79 (19%) required mechanical ventilation and one patient died. The EGRIS-kids was developed including: age, cranial nerve involvement and GBS disability score at admission, resulting in a 9 point score predicting risks of respiratory failure ranging from 4 to 50% (AUC = 0.71). A lower GBS disability score at nadir was the strongest predictor of recovery to independent walking (at one month: OR 0.43 95%CI 0.25-0.74).Conclusions: EGRIS-Kids and GBS disability score at admission accurately predict the risk of respiratory failure and inability to walk respectively in children with GBS, as tools to personalize the monitoring and treatment.

Angelman syndrome (AS) is a rare genetic disorder due to lack of UBE3A function on chromosome 15q11.2q13 caused by a deletion, uniparental paternal disomy (UPD), imprinting center disorder (ICD), or pathological variant of the UBE3A gene. AS is characterized by developmental delay, epilepsy, and lack of speech. Although fractures are observed frequently in our clinical practice, there are few studies on bone health in AS. The aim of this study is to investigate bone health in children with AS. In this prospective cohort study, we describe bone health in 91 children with AS visiting the ENCORE Expertise Center for AS between April 2010 and December 2021. Bone health was assessed with the bone health index (BHI) in standard deviation score (SDS) measured by digital radiogrammetry of the left hand using BoneXpert software. Risk factors analyzed were age, sex, genetic subtype, epilepsy, anti-seizure medication use, mobility, body mass index (BMI), and onset of puberty. Children with AS had a mean BHI of −1.77 SDS (SD 1.4). A significantly lower BHI was found in children with a deletion (−2.24 SDS) versus non-deletion (−1.02 SDS). Other factors associated with reduced BHI-SDS were inability to walk and late onset of puberty. Children with a history of one or more fractures (22%) had a significantly lower BHI than children without fractures (−2.60 vs −1.56 SDS). Longitudinal analysis showed a significant decrease in BHI-SDS with age in all genetic subtypes. Conclusions : Children with AS have a reduced bone health. Risk factors are deletion genotype, no independent walking, and late onset of puberty. Bone health decreased significantly with age. What is Known: • Children with neurological disorders often have a low bone health and higher risk of fractures. • Little is known about bone health in children with Angelman syndrome (AS). What is New: • Children with AS showed a reduced bone health and this was significantly associated with having a deletion, not being able to walk independently, and late onset of puberty. • Longitudinal analysis showed a significant decrease in bone health as children got older.

Background & aims: The aim of this study was to investigate the effect of a behavioral intervention on sleep problems, which are significant and an unmet clinical need in children with Angelman Syndrome (AS).Methods & procedures: Children (2-18 years) with AS and sleep problems were randomized to a behavioral intervention program or a control group. Intervention consisted of a standardized program including home visits, psycho-education, feedback based on direct observation of bedtime routine and video footage of the night and behavioral treatment techniques by a behavioral therapist. Change in sleep duration (primary) and parental sleep, nighttime visits, sleep hygiene, daytime behavior, parental stress and quality of life (secondary) were assessed post-intervention and at follow-up using questionnaires, diary, actigraphy and videosomnography.Outcomes & results: The groups, 9 children in each, did not differ at baseline. We found a sig-nificant effect of intervention on wake after sleep onset with classical statistical analysis (vid-eosomnography). With single case analysis we found a positive effect on total sleep time (diary and actigraphy) and wake after sleep onset (diary) with a persistent effect on total sleep time (actigraphy) and wake after sleep onset (diary). On secondary outcome there was a significant and persistent effect on sleep hygiene and several quality of life domains. Conclusions & implications: Behavioral intervention has a positive and persistent effect on sleep problems in children with AS. We advise psycho-education for all parents and use of video-somnography for both evaluation of and feedback on sleep behavior patterns, individual behavioral advice and specific behavioral techniques for children with sleep problems.

Angelman Syndrome (AS) is a rare genetic disorder caused by lack of maternal UBE3A protein due to a deletion of the chromosome 15q11.2-q13 region, uniparental paternal disomy, imprinting center defect, or pathogenic variant in the UBE3A gene. Characteristics are developmental delay, epilepsy, behavioral, and sleep problems. There is some evidence for hyperphagia, shorter stature, and higher BMI compared to neurotypical children, but longitudinal studies on growth are lacking. In this study, we analyzed prospectively collected data of 145 children with AS, who visited the ENCORE Expertise Center between 2010 and 2021, with a total of 853 visits. Children showed an elevated mean score of 25 on the Dykens Hyperphagia questionnaire (range 11–55) without genotype association. Higher scores were significantly associated with higher body mass index (BMI) standard deviation scores (SDS) (p = 0.004). Mean height was −1.2 SDS (SD 1.3), mean BMI-SDS was 0.6 (SD 1.7); 43% had a BMI-SDS > 1 and 20% had a BMI-SDS > 2. Higher BMI-SDS was significantly associated with non-deletion genotype (p = 0.037) and walking independently (p = 0.023). Height SDS decreased significantly with age (p < 0.001) and BMI-SDS increased significantly with age (p < 0.001. Onset of puberty was normal. In conclusion, children with AS showed moderate hyperphagia, lower height SDS, and higher BMI-SDS compared to norm data, with increasing deviation from the norm with age. It is uncertain how loss of maternal UBE3A function may influence growth. Attention to diet, exercise, and hyperphagia from an early age is recommended to prevent obesity and associated health problems.