Development, behaviour and sensory processing in Marshall-Smith syndrome and Malan syndrome: phenotype comparison in two related syndromes

Management of an older Marshall-Smith syndrome patient: a review of literature of MSS and craniosynostosis

Marshall-Smith Syndrome (MSS) is a rare progressive developmental disorder that severely impairs a patient's intellectual development and physical health. The only known cause for MSS is a mutation in the nuclear factor 1 X (NFIX) gene. This mutation affects neuronal development and protein transcription. Historically, most patients with MSS do not survive beyond 3 years of age. Reports of ocular findings are limited. We report a case of a 9-year-old MSS patient with progressive craniosynostosis, elevated intracranial pressure, and catastrophic ocular complications. A comprehensive PubMed literature search from 2018 to August 2022 updating a previous review of older literature produced 72 articles relating to MSS, which are reviewed.

Natural history in Malan syndrome: survey of 28 adults and literature review

BACKGROUND

Malan syndrome (MALNS), previously referred to as "Sotos syndrome 2" due to its resemblance to Sotos syndrome (SS), is an ultra-rare neurodevelopmental disorder characterized by overgrowth, typical craniofacial features, intellectual disability (ID), and a range of psychobehavioral, musculoskeletal, vision and neurological signs. As MALNS and SS partly overlap, it is essential to more accurately profile their clinical presentations and highlight their differences in order to improve syndrome specific management. An increasing number of individuals with MALNS reach adult-age though the natural history of the disorder is poorly characterized due to the small number of adult individuals described so far. As a consequence, current guidelines are limited to the pediatric population. Further delineation of MALNS is essential to optimize care in adulthood.

RESULTS

A mixed approach based on cross-sectional data collection with a survey disseminated to caregivers of adults with molecularly confirmed MALNS and literature review was conducted. Twenty-eight caregivers completed the survey. Clinical presentation in adulthood is multisystemic and defined by psychobehavioral comorbidities (96%), musculoskeletal involvement (96%), vision impairment (96%) and neurological complications (86%). The most common signs were anxiety (79%), hypotonia (75%), movement difficulty (75%), scoliosis (64%), problems with coordination (61%), strabismus (57%), constipation (54%), breastbone abnormalities (54%) and advanced bone age during childhood (54%). Impaired vision was complicated by vision decline (36%) and optic atrophy (32%). We report some previously unidentified features, including high pain threshold (46%), incontinence (25%), tremors (21%), muscle hypoplasia (18%) and tics (18%).

CONCLUSIONS

This survey in the adult population has allowed a more complete description of the natural history of MALNS. Our findings will contribute to the development and improvement of standards of care for adults with MALNS to assure optimal health monitoring and treatment of evolutive complications. We propose additional recommendations to the previous dataset of clinical evaluations specifically applied to adults. The comparison of MALNS and SS adult presentation highlights significant differences in terms of prevalence and severity of ID, behavioral issues, and vision problems, confirming that a proper differential diagnosis between the two conditions is indispensable to guide physicians and mental health professionals to syndrome specific management.

[NFIX gene mutation causes Marshall-Smith syndrome in a pair of identical twins and literature review]

This article reports on the clinical and genetic characteristics of monozygotic twins with Marshall-Smith syndrome (MRSHSS) due to a mutation in the NFIX gene, along with a review of related literature. Both patients presented with global developmental delays, a prominent forehead, shallow eye sockets, and pectus excavatum. Genetic testing revealed a heterozygous splicing site mutation c.697+1G>A in both children, with parents showing wild-type at this locus. According to the guidelines of the American College of Medical Genetics and Genomics, this mutation is considered likely pathogenic and has not been previously reported in the literature. A review of the literature identified 32 MRSHSS patients with splicing/frameshift mutations. Accelerated bone maturation and moderate to severe global developmental delay/intellectual disability are the primary clinical manifestations of patients with MRSHSS. Genetic testing results are crucial for the diagnosis of this condition.

Novel molecular mechanism in Malan syndrome uncovered through genome sequencing reanalysis, exon-level Array, and RNA sequencing

The NFIX gene encodes a DNA-binding protein belonging to the nuclear factor one (NFI) family of transcription factors. Pathogenic variants of NFIX are associated with two autosomal dominant Mendelian disorders, Malan syndrome (MIM 614753) and Marshall-Smith syndrome (MIM 602535), which are clinically distinct due to different disease-causing mechanisms. NFIX variants associated with Malan syndrome are missense variants mostly located in exon 2 encoding the N-terminal DNA binding and dimerization domain or are protein-truncating variants that trigger nonsense-mediated mRNA decay (NMD) resulting in NFIX haploinsufficiency. NFIX variants associated with Marshall-Smith syndrome are protein-truncating and are clustered between exons 6 and 10, including a recurrent Alu-mediated deletion of exons 6 and 7, which can escape NMD. The more severe phenotype of Marshall-Smith syndrome is likely due to a dominant-negative effect of these protein-truncating variants that escape NMD. Here, we report a child with clinical features of Malan syndrome who has a de novo NFIX intragenic duplication. Using genome sequencing, exon-level microarray analysis, and RNA sequencing, we show that this duplication encompasses exons 6 and 7 and leads to NFIX haploinsufficiency. To our knowledge, this is the first reported case of Malan Syndrome caused by an intragenic NFIX duplication.

Development of webcam-collected and artificial-intelligence-derived social and cognitive performance measures for neurodevelopmental genetic syndromes

This study focused on the development and initial psychometric evaluation of a set of online, webcam-collected, and artificial intelligence-derived patient performance measures for neurodevelopmental genetic syndromes (NDGS). Initial testing and qualitative input was used to develop four stimulus paradigms capturing social and cognitive processes, including social attention, receptive vocabulary, processing speed, and single-word reading. The paradigms were administered to a sample of 375 participants, including 163 with NDGS, 56 with idiopathic neurodevelopmental disability (NDD), and 156 neurotypical controls. Twelve measures were created from the four stimulus paradigms. Valid completion rates varied from 87 to 100% across measures, with lower but adequate completion rates in participants with intellectual disability. Adequate to excellent internal consistency reliability (α = 0.67 to 0.95) was observed across measures. Test-retest reproducibility at 1-month follow-up and stability at 4-month follow-up was fair to good (r = 0.40-0.73) for 8 of the 12 measures. All gaze-based measures showed evidence of convergent and discriminant validity with parent-report measures of other cognitive and behavioral constructs. Comparisons across NDGS groups revealed distinct patterns of social and cognitive functioning, including people with PTEN mutations showing a less impaired overall pattern and people with SYNGAP1 mutations showing more attentional, processing speed, and social processing difficulties relative to people with NFIX mutations. Webcam-collected performance measures appear to be a reliable and potentially useful method for objective characterization and monitoring of social and cognitive processes in NDGS and idiopathic NDD. Additional validation work, including more detailed convergent and discriminant validity analyses and examination of sensitivity to change, is needed to replicate and extend these observations.

A rare cause of intellectual disability: Novel mutations of NFIX gene in two patients with clinical features of Marshall-Smith syndrome and Malan syndrome

Marshall-Smith syndrome (MSS) and Malan syndrome (MS) are both allelic disorders caused by mutations in the NFIX gene. MS is characterized by overgrowth, intellectual disability, distinctive facial features, and accelerated skeletal maturation. On the other hand, clinical features of MSS consist of advanced bone age, dysmorphic features, intellectual disability, and failure to thrive at birth. In this study, we presented the clinical and molecular findings of two different patients with MS and MSS as a rare cause of intellectual disability and reported two novel variants in the NFIX gene. NFIX gene sequencing revealed a novel heterozygous c.1287delC (p.G430Vfs*34) mutation in patient 1 whose clinical diagnosis was compatible with Marshall-Smith syndrome, and in the second patient, physical features consistent with Malan syndrome, was detected a heterozygous one nucleotide duplication, c.303dupC (pCys102LeufsTer17).

A Mouse Model with a Frameshift Mutation in the Nuclear Factor I/X (NFIX) Gene Has Phenotypic Features of Marshall-Smith Syndrome

The nuclear factor I/X (NFIX) gene encodes a ubiquitously expressed transcription factor whose mutations lead to two allelic disorders characterized by developmental, skeletal, and neural abnormalities, namely, Malan syndrome (MAL) and Marshall-Smith syndrome (MSS). NFIX mutations associated with MAL mainly cluster in exon 2 and are cleared by nonsense-mediated decay (NMD) leading to NFIX haploinsufficiency, whereas NFIX mutations associated with MSS are clustered in exons 6-10 and escape NMD and result in the production of dominant-negative mutant NFIX proteins. Thus, different NFIX mutations have distinct consequences on NFIX expression. To elucidate the in vivo effects of MSS-associated NFIX exon 7 mutations, we used CRISPR-Cas9 to generate mouse models with exon 7 deletions that comprised: a frameshift deletion of two nucleotides (Nfix Del2); in-frame deletion of 24 nucleotides (Nfix Del24); and deletion of 140 nucleotides (Nfix Del140). Nfix +/Del2, Nfix +/Del24, Nfix +/Del140, Nfix Del24/Del24, and Nfix Del140/Del140 mice were viable, normal, and fertile, with no skeletal abnormalities, but Nfix Del2/Del2 mice had significantly reduced viability (p < 0.002) and died at 2-3 weeks of age. Nfix Del2 was not cleared by NMD, and NfixDel2/Del2 mice, when compared to Nfix +/+ and Nfix +/Del2 mice, had: growth retardation; short stature with kyphosis; reduced skull length; marked porosity of the vertebrae with decreased vertebral and femoral bone mineral content; and reduced caudal vertebrae height and femur length. Plasma biochemistry analysis revealed Nfix Del2/Del2 mice to have increased total alkaline phosphatase activity but decreased C-terminal telopeptide and procollagen-type-1-N-terminal propeptide concentrations compared to Nfix +/+ and Nfix +/Del2 mice. Nfix Del2/Del2 mice were also found to have enlarged cerebral cortices and ventricular areas but smaller dentate gyrus compared to Nfix +/+ mice. Thus, Nfix Del2/Del2 mice provide a model for studying the in vivo effects of NFIX mutants that escape NMD and result in developmental abnormalities of the skeletal and neural tissues that are associated with MSS. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Development of informant-report neurobehavioral survey scales for PTEN hamartoma tumor syndrome and related neurodevelopmental genetic syndromes

There are few well-validated measures that are appropriate for assessing the full range of neurobehavioral presentations in PTEN hamartoma tumor syndrome (PHTS) and other neurodevelopmental genetic syndromes (NDGS). As potential therapeutics are developed, having reliable, valid, free, and easily accessible measures to track a range of neurobehavioral domains will be crucial for future clinical trials. This study focused on the development and initial psychometric evaluation of a set of freely available informant-report survey scales for PHTS-the Neurobehavioral Evaluation Tool (NET). Concept elicitation, quantitative ratings, and cognitive interviewing processes were conducted with stakeholders and clinician-scientist experts, used to identify the most important neurobehavioral domains for this population, and to ensure items were appropriate for the full range of individuals with PHTS. Results of this process identified a PHTS neurobehavioral impact model with 11 domains. The final NET scales assessing these domains were administered to a sample of 384 participants (median completion time = 20.6 min), including 32 people with PHTS, 141 with other NDGS, 47 with idiopathic neurodevelopmental disorder (NDD), and 164 neurotypical controls. Initial psychometric results for the total scores of each scale indicated very good model (ω = 0.83-0.99) and internal consistency reliability (α = 0.82-0.98) as well as excellent test-retest reproducibility at 1-month follow-up (r = 0.78-0.98) and stability at 4-month follow-up (r = 0.76-0.96). Conditional reliability estimates indicated very strong measurement precision in key score ranges for assessing PHTS and other people with NDGS and/or idiopathic NDD. Comparisons across domains between PHTS and the other groups revealed specific patterns of symptoms and functioning, including lower levels of challenging behavior and more developed daily living and executive functioning skills relative to other NDGS. The NET appears to be a reliable and potentially useful tool for clinical characterization and monitoring of neurobehavioral symptoms in PHTS and may also have utility in the assessment of other NDGS and idiopathic NDD. Additional validation work, including convergent and discriminant validity analyses, are needed to replicate and extend these observations.

Sensory processing in 16p11.2 deletion and 16p11.2 duplication

Deletions and duplications at the chromosomal region of 16p11.2 have a broad range of phenotypic effects including increased likelihood of intellectual disability, autism, attention deficit hyperactivity disorder (ADHD), epilepsy, and language and motor delays. However, whether and how sensory processing is affected has not yet been considered in detail. Parents/caregivers of 38 children with a 16p11.2 deletion and 31 children with a 16p11.2 duplication completed the Sensory Behavior Questionnaire (SBQ) and the Child Sensory Profile 2 (CSP-2) along with other standardized questionnaires assessing autistic traits (SRS-2), ADHD traits (Conners 3), anxiety (SCAS-P) and adaptive behavior (VABS-3). SBQ and CSP-2 responses found that sensory processing differences were clearly evident in both 16p11.2 deletion and 16p11.2 duplication, though there was significant variation in both cohorts. SBQ data indicated the frequency and impact of sensory behavior were more severe when compared to neurotypical children, with levels being similar to autistic children. CSP-2 data indicated over 70% of children displayed clear differences in sensory registration (missing sensory input). Seventy-one percent with 16p11.2 duplications were also unusually sensitive to sensory information and 57% with 16p11.2 duplications were unusually avoidant of sensory stimuli. This first detailed assessment of sensory processing, alongside other clinical features, in relatively large cohorts of children with a 16p11.2 deletion and 16p11.2 duplication demonstrates that sensory processing differences have a profound impact on their lives.

Sensory Profile of Children and Adolescents with Autism Spectrum Disorder and Tip-Toe Behavior: Results of an Observational Pilot Study

Atypical sensory processing is frequently reported in persons with autism spectrum disorders (ASD), and it is one of the described diagnostic criteria for ASD. There is also mounting literature supporting the presence of motor impairments in individuals with ASD. Among these motor signs, tip-toe behavior (TTB) is a possible clinical finding, but its etiology is not clearly understood. It is suggested that TTB in ASD could be a sign of a sensory modulation impairment, but evidence is lacking and controversial. The main aim of this pilot study is to explore sensory features in a sample (4 females; 28 males) of children and adolescents with ASD (age range: 7-18). All participants also presented Intellectual Disability. Participants were divided in two groups, matched for age and gender, on the basis of the presence or absence of TTB (16 ASD TTB group vs. 16 ASD NO-TTB group) and then evaluated by using the Short Sensory Profile. We found that both ASD groups tend to significantly present sensory-related behavioral symptoms, but ASD TTB individuals more frequently showed the specific pattern of "under responsive/seeks sensation" than ASD NO-TTB individuals. These preliminary findings support that sensory-motor features might be taken into consideration when rehabilitation for TTB in children and adolescents with ASD is necessary.

Hydrocephalus in Nfix−/− Mice Is Underpinned by Changes in Ependymal Cell Physiology

Nuclear factor one X (NFIX) is a transcription factor required for normal ependymal development. Constitutive loss of Nfix in mice (Nfix−/−) is associated with hydrocephalus and sloughing of the dorsal ependyma within the lateral ventricles. Previous studies have implicated NFIX in the transcriptional regulation of genes encoding for factors essential to ependymal development. However, the cellular and molecular mechanisms underpinning hydrocephalus in Nfix−/− mice are unknown. To investigate the role of NFIX in hydrocephalus, we examined ependymal cells in brains from postnatal Nfix−/− and control (Nfix+/+) mice using a combination of confocal and electron microscopy. This revealed that the ependymal cells in Nfix−/− mice exhibited abnormal cilia structure and disrupted localisation of adhesion proteins. Furthermore, we modelled ependymal cell adhesion using epithelial cell culture and revealed changes in extracellular matrix and adherens junction gene expression following knockdown of NFIX. Finally, the ablation of Nfix from ependymal cells in the adult brain using a conditional approach culminated in enlarged ventricles, sloughing of ependymal cells from the lateral ventricles and abnormal localisation of adhesion proteins, which are phenotypes observed during development. Collectively, these data demonstrate a pivotal role for NFIX in the regulation of cell adhesion within ependymal cells of the lateral ventricles.

Characterization of Cognitive, Language and Adaptive Profiles of Children and Adolescents with Malan Syndrome

Malan Syndrome (MS) is an ultra-rare overgrowth genetic syndrome due to heterozygous variants or deletions in the Nuclear Factor I X (NFIX) gene. It is characterized by an unusual facial phenotype, generalized overgrowth, intellectual disability (ID) and behavioral problems. Even though limitations in cognitive and adaptive functioning have been previously described, systematic studies on MS cohorts are still lacking. Here, we aim to define the cognitive and adaptive behavior profile of MS children and adolescents, providing quantitative data from standardized evaluations. Subjects included in this study were evaluated from October 2020 to January 2022 and the study is based on a retrospective data archive: fifteen MS individuals were recruited and underwent evaluation with Wechsler Intelligence Scales, Leiter International Performance Scales and Griffith Mental Development Scales for cognitive profiles and with Vineland Adaptive Behavior Scales-II Edition (VABS-II) for adaptive functioning. Language skills and visuomotor integration abilities were assessed too. Comparisons and correlations between scales and subtests were performed. All the assessed MS individuals showed both low cognitive and adaptive functioning. One subject presented with mild ID, five had moderate ID and eight showed severe ID. One female toddler received a diagnosis of psychomotor delay. Linguistic skills were impaired in all individuals, with language comprehension relatively more preserved. Results revealed significant differences between VABS-II subdomains and a strong relationship between cognitive and adaptive functioning. All subjects exhibited mild to moderate ID and adaptive behavior lower than normal, with communication skills being the most affected. Regarding the daily living skills domain, personal and community subscale scores were dramatically lower than for the domestic subdomain, highlighting the importance of considering behavior within developmental and environmental contexts. Our cognitive and adaptive MS characterization provides a more accurate quantitative MS profiling, which is expected to help clinicians to better understand the complexity of this rare disorder.

A deep phenotyping experience: up to date in management and diagnosis of Malan syndrome in a single center surveillance report

Background

Malan syndrome (MALNS) is a recently described ultrarare syndrome lacking guidelines for diagnosis, management and monitoring of evolutive complications. Less than 90 patients are reported in the literature and limited clinical information are available to assure a proper health surveillance.

Results

A multidisciplinary team with high expertise in MALNS has been launched at the “Ospedale Pediatrico Bambino Gesù”, Rome, Italy. Sixteen Italian MALNS individuals with molecular confirmed clinical diagnosis of MALNS were enrolled in the program. For all patients, 1-year surveillance in a dedicated outpatient Clinic was attained. The expert panel group enrolled 16 patients and performed a deep phenotyping analysis directed to clinically profiling the disorder and performing critical revision of previously reported individuals. Some evolutive complications were also assessed. Previously unappreciated features (e.g., high risk of bone fractures in childhood, neurological/neurovegetative symptoms, noise sensitivity and Chiari malformation type 1) requiring active surveillance were identified. A second case of neoplasm was recorded. No major cardiovascular anomalies were noticed. An accurate clinical description of 9 new MALNS cases was provided.

Conclusions

Deep phenotyping has provided a more accurate characterization of the main clinical features of MALNS and allows broadening the spectrum of disease. A minimal dataset of clinical evaluations and follow-up timeline has been proposed for proper management of patients affected by this ultrarare disorder.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02384-9.