GABBR1 monoallelic de novo variants linked to neurodevelopmental delay and epilepsy.

GABAB receptors are obligatory heterodimers responsible for prolonged neuronal inhibition in the central nervous system. The two receptor subunits are encoded by GABBR1 and GABBR2. Variants in GABBR2 have been associated with a Rett-like phenotype (MIM: 617903), epileptic encephalopathy (MIM: 617904), and milder forms of developmental delay with absence epilepsy. To date, however, no phenotypes associated with pathogenic variants of GABBR1 have been established. Through GeneMatcher, we have ascertained four individuals who each have a monoallelic GABBR1 de novo non-synonymous variant; these individuals exhibit motor and/or language delay, ranging from mild to severe, and in one case, epilepsy. Further phenotypic features include varying degrees of intellectual disability, learning difficulties, autism, ADHD, ODD, sleep disorders, and muscular hypotonia. We functionally characterized the four de novo GABBR1 variants, p.Glu368Asp, p.Ala397Val, p.Ala535Thr, and p.Gly673Asp, in transfected HEK293 cells. GABA fails to efficiently activate the variant receptors, most likely leading to an increase in the excitation/inhibition balance in the central nervous system. Variant p.Gly673Asp in transmembrane domain 3 (TMD3) renders the receptor completely inactive, consistent with failure of the receptor to reach the cell surface. p.Glu368Asp is located near the orthosteric binding site and reduces GABA potency and efficacy at the receptor. GABA exhibits normal potency but decreased efficacy at the p.Ala397Val and p.Ala535Thr variants. Functional characterization of GABBR1-related variants provides a rationale for understanding the severity of disease phenotypes and points to possible therapeutic strategies.

Responsiveness of the Scale for the Assessment and Rating of Ataxia and Natural History in 884 Recessive and Early Onset Ataxia Patients.

OBJECTIVE: The Scale for the Assessment and Rating of Ataxia (SARA) is the most widely applied clinical outcome assessment (COA) for genetic ataxias, but presents metrological and regulatory challenges. To facilitate trial planning, we characterize its responsiveness (including subitem-level relations to ataxia severity and patient-focused outcomes) across a large number of ataxias, and provide first natural history data for several of them. METHODS: Subitem-level correlation and distribution-based analysis of 1,637 SARA assessments in 884 patients with autosomal recessive/early onset ataxia (370 with 2-8 longitudinal assessments) were complemented by linear mixed effects modeling to estimate progression and sample sizes. RESULTS: Although SARA subitem responsiveness varied between ataxia severities, gait/stance showed a robust granular linear scaling across the broadest range (SARA < 25). Responsiveness was diminished by incomplete subscale use at intermediate or upper levels, nontransitions ("static periods"), and fluctuating decreases/increases. All subitems except nose-finger showed moderate-to-strong correlations to activities of daily living, indicating that metric properties-not content validity-limit SARA responsiveness. SARA captured mild-to-moderate progression in many genotypes (eg, SYNE1-ataxia: 0.55 points/yr, ataxia with oculomotor apraxia type 2: 1.14 points/yr, POLG-ataxia: 1.56 points/yr), but no change in others (autosomal recessive spastic ataxia of Charlevoix-Saguenay, COQ8A-ataxia). Whereas sensitivity to change was optimal in mild ataxia (SARA < 10), it substantially deteriorated in advanced ataxia (SARA > 25; 2.7-fold sample size). Use of a novel rank-optimized SARA without subitems finger-chase and nose-finger reduces sample sizes by 20 to 25%. INTERPRETATION: This study comprehensively characterizes COA properties and annualized changes of the SARA across and within a large number of ataxias. It suggests specific approaches for optimizing its responsiveness that might facilitate regulatory qualification and trial design. ANN NEUROL 2023;94:470-485.

Parenting stress in families of children with disabilities: Impact of type of disability and assessment of attending paediatricians.

BACKGROUND: Parents of children with developmental disorders (DD) or disabilities report greater parenting stress than parents of typically developing children. To minimise this stress, stressful factors need to be known and stress needs to be recognised early. The present cross-sectional study aims to systematically assess and compare parenting stress in families of children with various types of disabilities. In addition, the assessment of parenting stress by attending paediatricians will be evaluated. METHODS: We surveyed 611 parents about their parenting stress at the Children's Development Center (CDC). Three questionnaires, including the German versions of the Parenting Stress Index (PSI) and Impact on Family Scale (IOFS), were used to evaluate parenting stress. Furthermore, attending paediatricians assessed of the child's type of disability and their perception of parenting stress in a separate questionnaire. RESULTS: Fifty-five percent of all parents reported stress at a clinically relevant level, 65% in the child domain and 39% in the parent domain of the PSI. Parenting stress differed significantly across diagnostic categories (p < 0.01) and was associated with childhood disability related issues of behaviour, sleep or feeding issues. Parenting stress was often underestimated by the paediatricians, especially when the children had disabilities perceived as less severe. In one-third of parents with clinically relevant total stress, paediatricians reported low stress levels. Parent-reported financial problems, social isolation, and partnership conflicts were not suspected by paediatricians in ≥85% of cases. CONCLUSIONS: Clinically relevant parenting stress was found more often than in comparable studies. An assessment of parenting stress by paediatricians may be complicated by time constraints in medical appointments, the mainly child-centred consultation, or restricted expression of parents' stress. Paediatricians should move from a purely child-centred to a holistic, family-centred approach to treatment. Routine screening of parenting stress using standardised questionnaires could be helpful to identify affected families.

Expanding SPTAN1 monoallelic variant associated disorders: From epileptic encephalopathy to pure spastic paraplegia and ataxia.

PURPOSE: Nonerythrocytic αII-spectrin (SPTAN1) variants have been previously associated with intellectual disability and epilepsy. We conducted this study to delineate the phenotypic spectrum of SPTAN1 variants. METHODS: We carried out SPTAN1 gene enrichment analysis in the rare disease component of the 100,000 Genomes Project and screened 100,000 Genomes Project, DECIPHER database, and GeneMatcher to identify individuals with SPTAN1 variants. Functional studies were performed on fibroblasts from 2 patients. RESULTS: Statistically significant enrichment of rare (minor allele frequency < 1 × 10-5) probably damaging SPTAN1 variants was identified in families with hereditary ataxia (HA) or hereditary spastic paraplegia (HSP) (12/1142 cases vs 52/23,847 controls, p = 2.8 × 10-5). We identified 31 individuals carrying SPTAN1 heterozygous variants or deletions. A total of 10 patients presented with pure or complex HSP/HA. The remaining 21 patients had developmental delay and seizures. Irregular αII-spectrin aggregation was noted in fibroblasts derived from 2 patients with p.(Arg19Trp) and p.(Glu2207del) variants. CONCLUSION: We found that SPTAN1 is a genetic cause of neurodevelopmental disorder, which we classified into 3 distinct subgroups. The first comprises developmental epileptic encephalopathy. The second group exhibits milder phenotypes of developmental delay with or without seizures. The final group accounts for patients with pure or complex HSP/HA.

The constitutional gain-of-function variant p.Glu1099Lys in NSD2 is associated with a novel syndrome.

NSD2 dimethylates histone H3 at lysine 36 (H3K36me2) and is located in the Wolf-Hirschhorn syndrome (WHS) critical region. Recent descriptions have delineated loss-of-function (LoF) variants in NSD2 with a distinct disorder. The oncogenic missense variant p.Glu1099Lys occurs somatically in leukemia and has a gain-of-function (GoF) effect. We describe two individuals carrying p.Glu1099Lys as heterozygous de novo germline variant identified by exome sequencing (ES) of blood DNA and subsequently confirmed in two ectodermal tissues. Clinically, these individuals are characterized by intellectual disability, coarse/ square facial gestalt, abnormalities of the hands, and organomegaly. Public cell lines with NSD2 GoF variants had increased K36me2, DNA promoter methylation, and dysregulated RNA expression. NSD2 GoF caused by p.Glu1099Lys is associated with a novel phenotype different from WHS and Rauch-Steindl syndrome (RAUST).

Bi-allelic variants in CHKA cause a neurodevelopmental disorder with epilepsy and microcephaly.

The Kennedy pathways catalyse the de novo synthesis of phosphatidylcholine and phosphatidylethanolamine, the most abundant components of eukaryotic cell membranes. In recent years, these pathways have moved into clinical focus because four of ten genes involved have been associated with a range of autosomal recessive rare diseases such as a neurodevelopmental disorder with muscular dystrophy (CHKB), bone abnormalities and cone-rod dystrophy (PCYT1A) and spastic paraplegia (PCYT2, SELENOI). We identified six individuals from five families with bi-allelic variants in CHKA presenting with severe global developmental delay, epilepsy, movement disorders and microcephaly. Using structural molecular modelling and functional testing of the variants in a cell-based Saccharomyces cerevisiae model, we determined that these variants reduce the enzymatic activity of CHKA and confer a significant impairment of the first enzymatic step of the Kennedy pathway. In summary, we present CHKA as a novel autosomal recessive gene for a neurodevelopmental disorder with epilepsy and microcephaly.

Case Report: Deficiency of Adenosine Deaminase 2 (DADA2) as a Cause of Brainstem Stroke in a 3-Year-Old Girl and the Importance of Early Fast-Track Genetic Diagnostics to Influence Therapy.

Deficiency of adenosine deaminase 2 (DADA2) is a rare Mendelian, autoinflammatory multiorgan disease. We report the case of a 3.8-year-old female patient who was admitted with an acute brainstem stroke and was diagnosed with DADA2 by early initiation of exome sequencing. We recommend that DADA2 and a genetic workup should be taken into account, when evaluating strokes in children even if no other than neurological symptoms are evident.

CDK19-related disorder results from both loss-of-function and gain-of-function de novo missense variants.

PURPOSE: To expand the recent description of a new neurodevelopmental syndrome related to alterations in CDK19. METHODS: Individuals were identified through international collaboration. Functional studies included autophosphorylation assays for CDK19 Gly28Arg and Tyr32His variants and in vivo zebrafish assays of the CDK19G28R and CDK19Y32H. RESULTS: We describe 11 unrelated individuals (age range: 9 months to 14 years) with de novo missense variants mapped to the kinase domain of CDK19, including two recurrent changes at residues Tyr32 and Gly28. In vitro autophosphorylation and substrate phosphorylation assays revealed that kinase activity of protein was lower for p.Gly28Arg and higher for p.Tyr32His substitutions compared with that of the wild-type protein. Injection of CDK19 messenger RNA (mRNA) with either the Tyr32His or the Gly28Arg variants using in vivo zebrafish model significantly increased fraction of embryos with morphological abnormalities. Overall, the phenotype of the now 14 individuals with CDK19-related disorder includes universal developmental delay and facial dysmorphism, hypotonia (79%), seizures (64%), ophthalmologic anomalies (64%), and autism/autistic traits (56%). CONCLUSION: CDK19 de novo missense variants are responsible for a novel neurodevelopmental disorder. Both kinase assay and zebrafish experiments showed that the pathogenetic mechanism may be more diverse than previously thought.

Pitfalls in Genetic Diagnostics: Why Phenotyping is Essential.

New genetic testing technologies have revolutionized medicine within the past years. It is foreseeable that the development will continue with the introduction of new techniques. Nevertheless, despite improved technology, an exact clinical description of the phenotype is still necessary and it is important to critically question findings, both before initiating genetic testing and when interpreting the results. We present four brief case vignettes to point out difficulties associated with correctly interpreting genetic findings.

Unusual mechanical failures of intrathecal baclofen pump systems: symptoms, signs, and trouble shooting.

INTRODUCTION: Although intrathecal baclofen (ITB) therapy is an effective treatment for spasticity, it has several disadvantages and a risk of complications. METHODS: We present six pediatric patients who suffered from unusual mechanical failures of intrathecal baclofen pump systems. RESULTS: With these case-vignettes, we provide a systematic approach on how to interpret the symptoms of ITB complications and an advice which further diagnostic and therapeutic steps to follow. We underline the seriousness of baclofen overdose, underdosing or withdrawal.

The "Ivy-Sign" in Moyamoya Disease-From MRI Pattern to Diagnosis.

Moyamoya disease (MMD) is characterized by bilateral, chronic progressive stenosis at the terminal portions of the internal carotid arteries and their proximal branches. The "smoke-like" appearance of the arterial collaterals in angiography gives the disease its name. The "ivy-sign" is the less-known magnetic resonance imaging (MRI) pattern of this disease. The leptomeningeal collaterals present as diffuse signal enhancement at the brain surface in contrast-enhanced T1-weighted image and fluid-attenuated inversion recovery sequences "as if overgrown with ivy."We report on three patients with MMD in whom the "ivy-sign" was already present but misinterpreted in the initial MRI of the brain. The correct diagnosis was made only after repeated MRI.Using three case studies, we describe the difficulties in the interpretation of the "ivy-sign" as an MRI pattern. Knowledge of the "ivy-sign" can be helpful, especially in diseases predisposing to MMD. If this MRI pattern is present, MMD should be considered and MR angiography should be added.

Comparative Analysis of Cerebral Magnetic Resonance Imaging Changes in Nontreated Infantile, Juvenile and Adult Patients with Niemann-Pick Disease Type C.

AIM: The study aims to describe cerebral MRI in different onset forms of Niemann-Pick type C (NPC). Systematic MRI analyses in this rare lysosomal storage disease are lacking in the infantile and juvenile onset forms. METHODS: Thirty-two cerebral MRI scans from 19 patients with NPC were assessed using a newly established and validated scoring system which addresses white matter changes and supratentorial versus infratentorial atrophy. RESULTS: Seven scans were from six NPC patients with early infantile onset (<2 years of age), six scans were from three patients with late infantile onset (2-6 years), six scans from four with juvenile onset (6-15 years), and 13 from six with adult onset (>15 years). While supratentorial atrophy was the leading sign in the infantile groups, the juvenile and adult forms were characterized by both, infra- and supratentorial atrophy. White matter changes were found in nearly every patient; they increased with the disease duration in the earlier forms and were prominent in the later forms already early in the disease course. CONCLUSION: This is the first systematic and comparative MRI analysis in the different onset groups of NPC using a scoring system. Early during disease course, MRI showed different patterns in infantile compared with juvenile and adult onset NPC patients, for example, only supratentorial atrophy in juvenile versus global atrophy in adult onset patients. MRI changes provide an additional, early biomarker for NPC.

Oligoclonal bands predict multiple sclerosis in children with optic neuritis.

We retrospectively evaluated predictors of conversion to multiple sclerosis (MS) in 357 children with isolated optic neuritis (ON) as a first demyelinating event who had a median follow-up of 4.0 years. Multiple Cox proportional-hazards regressions revealed abnormal cranial magnet resonance imaging (cMRI; hazard ratio [HR] = 5.94, 95% confidence interval [CI] = 3.39-10.39, p < 0.001), presence of cerebrospinal fluid immunoglobulin G oligoclonal bands (OCB; HR = 3.69, 95% CI = 2.32-5.86, p < 0.001), and age (HR = 1.08 per year of age, 95% CI = 1.02-1.13, p = 0.003) as independent predictors of conversion, whereas sex and laterality (unilateral vs bilateral) had no influence. Combined cMRI and OCB positivity indicated a 26.84-fold higher HR for developing MS compared to double negativity (95% CI = 12.26-58.74, p < 0.001). Accordingly, cerebrospinal fluid analysis may supplement cMRI to determine the risk of MS in children with isolated ON.

Mutations in POLR3A and POLR3B are a major cause of hypomyelinating leukodystrophies with or without dental abnormalities and/or hypogonadotropic hypogonadism.

BACKGROUND: Leukodystrophies are a heterogeneous group of inherited neurodegenerative disorders characterised by abnormal central nervous system white matter. Mutations in POLR3A and POLR3B genes were recently reported to cause four clinically overlapping hypomyelinating leukodystrophy phenotypes. Our aim was to investigate the presence and frequency of POLR3A and POLR3B mutations in patients with genetically unexplained hypomyelinating leukodystrophies with typical clinical and/or radiologic features of Pol III-related leukodystrophies. METHODS: The entire coding region and the flanking exon/intron boundaries of POLR3A and/or POLR3B genes were amplified and sequenced in 14 patients. RESULTS: Recessive mutations in POLR3A or POLR3B were uncovered in all 14 patients. Eight novel mutations were identified in POLR3A: six missenses, one nonsense, and one frameshift mutation. Seven patients carried compound heterozygous mutations in POLR3B, of whom six shared the common mutation in exon 15 (p.V523E). Seven novel mutations were identified in POLR3B: four missenses, two splice sites, and one intronic mutation. CONCLUSIONS: To date, our group has described 37 patients, of whom 27 have mutations in POLR3A and 10 in POLR3B, respectively. Altogether, our results further support the proposal that POLR3A and POLR3B mutations are a major cause of hypomyelinating leukodystrophies and suggest that POLR3A mutations are more frequent.

Still an Unsolved Question: The Place of Cranial Magnetic Resonance Imaging in Acute Acquired Concomitant Esotropia.

PURPOSE: The aim of this study was to collect further data to estimate the risk of relevant intracranial pathology and thereby better assess the need for cranial imaging in children with acute acquired comitant esotropia (AACE). To date, there is still not enough literature on this topic to enable a consensus on the diagnostic algorithm. METHODS: We analyzed data from patients with convergent strabismus who received cranial imaging via magnetic resonance imaging (MRI). Twenty-one patients received a cranial MRI for the diagnostic evaluation of AACE. The age range was from 2 to 12 years, and the mean age at the time of diagnosis was 5.5 years. Of these patients, only one exhibited insignificant MRI findings, with no therapeutic consequences. CONCLUSIONS: Our data add further evidence that AACE without neurological findings or other ophthalmologic anomalies might not be an indication for cranial MRI as a diagnostic screening tool.

The Impact of Demographic Characteristics on Parenting Stress among Parents of Children with Disabilities: A Cross-Sectional Study.

Even though it is already known that parents of children with developmental delays or disabilities experience higher parenting stress than families of typically developing children, the contributing factors need to be analyzed in more detail. The aim of this cross-sectional study was to examine the influence of demographic characteristics on parenting stress from caring for a disabled child and to identify possible protective or additional stressful social factors. A total of 611 mothers and fathers of children with developmental delays, chronic diseases, or disabilities completed two questionnaires during their medical appointments at the Children's Development Center (CDC) of Leipzig University Hospital between June 2020 and February 2021. These consisted of the German versions of the Parenting Stress Index (PSI) and the Impact on Family Scale (IOFS). To determine differences between the various groups, we used parametric and non-parametric tests. Mothers and single parents are significantly more strained than fathers and non-single parents. Parents with vocational training, those who graduated with a higher-level diploma, and those within employment report a higher financial burden. While unemployed and full-time workers experience the lowest stress, parents who work part-time or exclusively take care of their child show higher levels of stress. Looking at the age of the child, parents of children of young primary school age are the most stressed, and those of infants are the least stressed. These findings suggest that mothers and single parents especially should receive more support, and parents need to be provided with more attention during their child's entry into school. Possible limitations and the influence of the COVID-19 pandemic are discussed.

Cerebrospinal Fluid Protein Concentrations in Hydrocephalus.

CSF protein levels are altered in neurological disorders, such as hydrocephalus of different etiologies. In this retrospective observational study, we analyzed cerebrospinal fluid (CSF) samples in hydrocephalic diseases such as aqueductal stenosis (AQS, n = 27), normal pressure hydrocephalus (NPH, n = 24), hydrocephalus communicans (commHC, n = 25) and idiopathic intracranial hypertension (IIH)/pseudotumor cerebri (PC, n = 7) in comparison with neurological patients without hydrocephalic configuration (control, n = 95). CSF was obtained through CSF diversion procedures and lumbar punction and analyzed for protein concentrations according to the institution's laboratory standards. We found significantly decreased CSF protein levels in patients suffering from AQS (0.13 mg/dL [0.1-0.16 mg/dL] p = 2.28 × 10-8) and from PC (0.18 mg/dL [0.12-0.24 mg/dL] p = 0.01) compared with controls (0.34 mg/dL [0.33-0.35 mg/dL]). Protein levels were not altered in patients suffering from commHC and NPH compared with neurologically healthy individuals. We propose that a decrease in CSF protein levels is part of an active counterregulatory mechanism to lower CSF volume and, subsequently, intracranial pressure in specific diseases. Research regarding said mechanism and more specific proteomic research on a cellular level must still be performed to prove this hypothesis. Differences in protein levels between different diseases point to different etiologies and mechanisms in different hydrocephalic pathologies.

Case report: Complete paternal isodisomy on chromosome 18 induces methylation changes in PARD6G-AS1 promotor in a case with arthrogryposis.

Uniparental disomy (UPD) is the inheritance of both alleles of a chromosome from only one parent. So far, the detection of UPDs in sequencing data is not well established and a known gap in next-generation sequencing (NGS) diagnostics. By developing a new tool for UPD detection, we re-evaluated an eight-year-old individual presenting with scoliosis, muscle weakness and global developmental delay. Previous panel analysis identified a homozygous likely pathogenic loss-of-function variant in the PIEZO2-gene associated with arthrogryposis (OMIM # 617146). Interestingly, during a re-evaluation process, we identified a region of homozygosity (ROH) covering over 95% of chromosome 18. Segregation and microsatellite analysis within the family revealed that only the father is a heterozygous carrier of the variant in PIEZO2 and confirmed paternal uniparental isodisomy (iUPD) on chromosome 18 in the individual. Further methylation analysis indicated demethylation of the promotor region of PARD6G-AS1, which is described to be maternally imprinted and could possibly influence the individuals' phenotype. Our report describes the first complete iUPD on chromosome 18 and highlights that UPDs can be a cause for homozygous pathogenic variants, which reduces the risk of reoccurrence in case of a new pregnancy in comparison to an autosomal recessive inheritance trait significantly.