Bi-allelic variants in SNF8 cause a disease spectrum ranging from severe developmental and epileptic encephalopathy to syndromic optic atrophy.

The endosomal sorting complex required for transport (ESCRT) machinery is essential for membrane remodeling and autophagy and it comprises three multi-subunit complexes (ESCRT I-III). We report nine individuals from six families presenting with a spectrum of neurodevelopmental/neurodegenerative features caused by bi-allelic variants in SNF8 (GenBank: NM_007241.4), encoding the ESCRT-II subunit SNF8. The phenotypic spectrum included four individuals with severe developmental and epileptic encephalopathy, massive reduction of white matter, hypo-/aplasia of the corpus callosum, neurodevelopmental arrest, and early death. A second cohort shows a milder phenotype with intellectual disability, childhood-onset optic atrophy, or ataxia. All mildly affected individuals shared the same hypomorphic variant, c.304G>A (p.Val102Ile). In patient-derived fibroblasts, bi-allelic SNF8 variants cause loss of ESCRT-II subunits. Snf8 loss of function in zebrafish results in global developmental delay and altered embryo morphology, impaired optic nerve development, and reduced forebrain size. In vivo experiments corroborated the pathogenicity of the tested SNF8 variants and their variable impact on embryo development, validating the observed clinical heterogeneity. Taken together, we conclude that loss of ESCRT-II due to bi-allelic SNF8 variants is associated with a spectrum of neurodevelopmental/neurodegenerative phenotypes mediated likely via impairment of the autophagic flux.

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.

Isovaleric aciduria identified by newborn screening: Strategies to predict disease severity and stratify treatment.

Newborn screening (NBS) allows early identification of individuals with rare disease, such as isovaleric aciduria (IVA). Reliable early prediction of disease severity of positively screened individuals with IVA is needed to guide therapeutic decision, prevent life-threatening neonatal disease manifestation in classic IVA and over-medicalization in attenuated IVA that may remain asymptomatic. We analyzed 84 individuals (median age at last study visit 8.5 years) with confirmed IVA identified by NBS between 1998 and 2018 who participated in the national, observational, multicenter study. Screening results, additional metabolic parameters, genotypes, and clinical phenotypic data were included. Individuals with metabolic decompensation showed a higher median isovalerylcarnitine (C5) concentration in the first NBS sample (10.6 vs. 2.7 µmol/L; p < 0.0001) and initial urinary isovalerylglycine concentration (1750 vs. 180 mmol/mol creatinine; p = 0.0003) than those who remained asymptomatic. C5 was in trend inversely correlated with full IQ (R = -0.255; slope = -0.869; p = 0.0870) and was lower for the "attenuated" variants compared to classic genotypes [median (IQR; range): 2.6 µmol/L (2.1-4.0; 0.7-6.4) versus 10.3 µmol/L (7.4-13.1; 4.3-21.7); N = 73]. In-silico prediction scores (M-CAP, MetaSVM, and MetaLR) correlated highly with isovalerylglycine and ratios of C5 to free carnitine and acetylcarnitine, but not sufficiently with clinical endpoints. The results of the first NBS sample and biochemical confirmatory testing are reliable early predictors of the clinical course of IVA, facilitating case definition (attenuated versus classic IVA). Prediction of attenuated IVA is supported by the genotype. On this basis, a reasonable algorithm has been established for neonates with a positive NBS result for IVA, with the aim of providing the necessary treatment immediately, but whenever possible, adjusting the treatment to the individual severity of the disease.

Newborn screening and disease variants predict neurological outcome in isovaleric aciduria.

Isovaleric aciduria (IVA), a metabolic disease with severe (classic IVA) or attenuated phenotype (mild IVA), is included in newborn screening (NBS) programs worldwide. The long-term clinical benefit of screened individuals, however, is still rarely investigated. A national, prospective, observational, multi-center study of individuals with confirmed IVA identified by NBS between 1998 and 2018 was conducted. Long-term clinical outcomes of 94 individuals with IVA were evaluated, representing 73.4% (for classic IVA: 92.3%) of the German NBS cohort. In classic IVA (N = 24), NBS prevented untimely death except in one individual with lethal neonatal sepsis (3.8%) but did not completely prevent single (N = 10) or recurrent (N = 7) metabolic decompensations, 13 of them occurring already neonatally. IQ (mean ± SD, 90.7 ± 10.1) was mostly normal but below the reference population (P = .0022) and was even lower in individuals with severe neonatal decompensations (IQ 78.8 ± 7.1) compared to those without crises (IQ 94.7 ± 7.5; P = .01). Similar results were obtained for school placement. In contrast, individuals with mild IVA had excellent neurocognitive outcomes (IQ 105.5 ± 15.8; normal school placement) and a benign disease course (no metabolic decompensation, normal hospitalization rate), which did not appear to be impacted by metabolic maintenance therapy. In conclusion, NBS reduces mortality in classic IVA, but does not reliably protect against severe neonatal metabolic decompensations, crucial for favorable neurocognitive outcome. In contrast, individuals with mild IVA had excellent clinical outcomes regardless of metabolic maintenance therapy, questioning their benefit from NBS. Harmonized stratified therapeutic concepts are urgently needed.

Recurrent Myalgia since Early Infancy-Misleading Clinical Course in a Child with Carnitine Palmitoyltransferase-II Deficiency.

Metabolic myopathies are heterogeneous hereditary diseases affecting skeletal muscle energy supply. Symptoms usually comprise pain, cramps, hypotonia, weakness, and myoglobinuria.We present a boy with recurrent myalgia and weakness after some minutes of exercise or during febrile infections since early infancy. First laboratory workup at the age of 9 years showed no abnormalities, apart from a slightly elevated creatine kinase. After exclusion of common structural and metabolic myopathies, next generation sequencing panel (4 years after the initial diagnostic metabolic workup) revealed two potentially pathogenic missense mutations in the CPT2 gene (c.149C > A (p.P50H) and c.1459G > A (p.E487K)).Our case underscores the clinical variability of muscle carnitine palmitoyltransferase II (CPT II) deficiency and illustrates a pitfall of diagnostic algorithms for metabolic myopathies. Myalgia following exercise of a few minutes duration would have argued for a carbohydrate and against a fatty acid metabolic defect. However, CPT II deficiency is the most common disorder of muscle fatty acid metabolism and should be considered even in atypical scenarios. Analyses of plasma acyl carnitine profile during acute metabolic crises may help to unmask biochemical markers which are often overlooked in dried-blood analyses.

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.

Complementing the phenotypical spectrum of TUBA1A tubulinopathy and its role in early-onset epilepsies.

TUBA1A tubulinopathy is a rare neurodevelopmental disorder associated with brain malformations as well as early-onset and intractable epilepsy. As pathomechanisms and genotype-phenotype correlations are not completely understood, we aimed to provide further insights into the phenotypic and genetic spectrum. We here present a multicenter case series of ten unrelated individuals from four European countries using systematic MRI re-evaluation, protein structure analysis, and prediction score modeling. In two cases, pregnancy was terminated due to brain malformations. Amongst the eight living individuals, the phenotypic range showed various severity. Global developmental delay and severe motor impairment with tetraparesis was present in 63% and 50% of the subjects, respectively. Epilepsy was observed in 75% of the cases, which showed infantile onset in 83% and a refractory course in 50%. One individual presented a novel TUBA1A-associated electroclinical phenotype with evolvement from early myoclonic encephalopathy to continuous spike-and-wave during sleep. Neuroradiological features comprised a heterogeneous spectrum of cortical and extracortical malformations including rare findings such as cobblestone lissencephaly and subcortical band heterotopia. Two individuals developed hydrocephalus with subsequent posterior infarction. We report four novel and five previously published TUBA1A missense variants whose resulting amino acid substitutions likely affect longitudinal, lateral, and motor protein interactions as well as GTP binding. Assessment of pathogenic and benign variant distributions in synopsis with prediction scores revealed sections of variant enrichment and intolerance to missense variation. We here extend the clinical, neuroradiological, and genetic spectrum of TUBA1A tubulinopathy and provide insights into residue-specific pathomechanisms and genotype-phenotype correlations.

Gain and loss of TASK3 channel function and its regulation by novel variation cause KCNK9 imprinting syndrome.

BACKGROUND: Genomics enables individualized diagnosis and treatment, but large challenges remain to functionally interpret rare variants. To date, only one causative variant has been described for KCNK9 imprinting syndrome (KIS). The genotypic and phenotypic spectrum of KIS has yet to be described and the precise mechanism of disease fully understood. METHODS: This study discovers mechanisms underlying KCNK9 imprinting syndrome (KIS) by describing 15 novel KCNK9 alterations from 47 KIS-affected individuals. We use clinical genetics and computer-assisted facial phenotyping to describe the phenotypic spectrum of KIS. We then interrogate the functional effects of the variants in the encoded TASK3 channel using sequence-based analysis, 3D molecular mechanic and dynamic protein modeling, and in vitro electrophysiological and functional methodologies. RESULTS: We describe the broader genetic and phenotypic variability for KIS in a cohort of individuals identifying an additional mutational hotspot at p.Arg131 and demonstrating the common features of this neurodevelopmental disorder to include motor and speech delay, intellectual disability, early feeding difficulties, muscular hypotonia, behavioral abnormalities, and dysmorphic features. The computational protein modeling and in vitro electrophysiological studies discover variability of the impact of KCNK9 variants on TASK3 channel function identifying variants causing gain and others causing loss of conductance. The most consistent functional impact of KCNK9 genetic variants, however, was altered channel regulation. CONCLUSIONS: This study extends our understanding of KIS mechanisms demonstrating its complex etiology including gain and loss of channel function and consistent loss of channel regulation. These data are rapidly applicable to diagnostic strategies, as KIS is not identifiable from clinical features alone and thus should be molecularly diagnosed. Furthermore, our data suggests unique therapeutic strategies may be needed to address the specific functional consequences of KCNK9 variation on channel function and regulation.

Psychological well-being of early and continuously treated phenylketonuria patients.

BACKGROUND: Despite enormous advances in therapy, phenylketonuria (PKU) remains an incurable, inherited metabolic disease requiring life-long treatment with potential to negatively impact quality of life and psychological well-being. Therefore, the aim of this study was to screen early diagnosed and continuously treated children with PKU on psychological strengths and behavioral difficulties. METHODS: Evaluation of psychological strengths and behavioral difficulties in 49 patients with PKU (23f, 2-17 years) by Strengths and Difficulties Questionnaire (SDQ; self-report 11-17 years and parent-report 2-17 years). Comparison to age, sex and BMI-matched healthy controls (n = 98; 46f). RESULTS: In patients with PKU and healthy controls median SDQ Total Difficulties Score and median scores of subscales were within the normal range in parent- and self-report, irrespective of sex and age group (children 2-10 years, adolescents 11-17 years). No influence of long-term metabolic control in PKU on SDQ could be revealed. The 2- to 10-year-old boys with PKU showed significantly higher scores in Prosocial Behavior compared to their healthy peers (P = .032). Likewise, adolescent boys with PKU showed fewer Conduct Problems (parent-report, P = .006). Adolescent girls with PKU rated themselves more often as abnormal in the subscale Emotional Problems compared to their healthy peers (P = .041). This subscale was also responsible for a significantly different Total SDQ Difficulties Score between patients and their parents' report (P = .008). DISCUSSION: SDQ represents a suitable instrument within the care for patients with PKU. Specific aspects, however, require separate consideration and evaluation with respect to this chronic disease. Special attention should be paid on adolescent PKU girls who seem to be at risk to develop emotional problem.

Growth and Final Height Among Children With Phenylketonuria.

BACKGROUND AND OBJECTIVES: Growth is an important criterion to evaluate health in childhood and adolescence, especially in patients depending on special dietary treatment. Phenylketonuria (PKU) is the most common inherited disease of amino acid metabolism. Patients with PKU depend on a special phenylalanine-restricted diet, low in natural protein. The study aimed to evaluate growth, growth rate, and target height in 224 patients with PKU. METHODS: Retrospective, longitudinal analysis of standardized, yearly measurements of height, weight, and calculated growth rate (SD score [SDS]) of patients with PKU aged 0 to 18 years were conducted by using the national computerized CrescNet database. Inclusion was restricted to patients carried to term with a confirmed diagnosis of PKU or mild hyperphenylalaninemia determined by newborn screening and early treatment initiation. RESULTS: From birth to adulthood, patients with PKU were significantly shorter than healthy German children (height SDS at 18 years: -0.882 ± 0.108, P < .001). They missed their target height by 3 cm by adulthood (women: P = .02) and 5 cm (men: P = .01). In patients receiving casein hydrolysate during childhood, this was more pronounced compared with patients receiving amino acid mixtures (P < .001). Growth rate was significantly reduced during their first 2 years of life and in puberty (growth rate SDS: -1.1 to -0.5 m/year, P < .001 and -0.5; P < .02). CONCLUSIONS: Early diagnosed, treated, and continuously monitored patients with PKU showed reduced height from birth onward. During the last 2 decades, this phenomenon attenuated, probably because of advances in PKU therapy related to protein supplements and special low-protein foods.

The challenge of long-term tetrahydrobiopterin (BH4) therapy in phenylketonuria: Effects on metabolic control, nutritional habits and nutrient supply.

BACKGROUND AND AIMS: BH4-sensitive phenylketonuria (PKU) patients relax their phenylalanine (Phe) restricted diet due to increased Phe tolerance, while keeping dried blood Phe concentrations with in the therapeutic range. We aimed to investigate metabolic control, eating habits and nutrient supply under long-term BH4-therapy. PATIENTS AND METHODS: Retrospective analysis of mean dried blood Phe concentrations and their variability, food and nutrient intake in BH4-sensitive patients (n = 8, 3f, age 6.0-16.6 y) under classical dietary treatment for one year and during the three years after initiation of BH4. RESULTS: Phe concentrations of BH4-sensitve PKU patients remained within therapeutic range throughout the observation period, independent of therapeutic regime. Under BH4, Phe tolerance increased significantly (493.2 ± 161.8 mg/d under classical diet vs 2021.93 ± 897.4 mg/d two years under BH4; P = 0.004). Variability of Phe concentrations remained unchanged (mean SD; P = 1.000). Patients adjust their food choice and significantly increased their intake of cereals, potatoes, dairy products and meat (P = 0.019, P = 0.016, P = 0.016 and P = 0.016, respectively). Under diet changes after implementation of BH4 a drop in micronutrient intake (vitamin D, folic acid, iron, calcium, iodine) could be revealed (P = 0.005, P < 0.001, P = 0.004, P = 0.001, P = 0.003, respectively). CONCLUSIONS: BH4-sensitive PKU patients can achieve good metabolic control under an adjuvant BH4- or a BH4 monotherapy. The liberalized diet under BH4 seems to jeopardize the quality of patients' nutrition, and these patients require close follow-up and special nutrition education to minimize the risk for imbalanced diet and nutrient deficiencies.

Genome-wide linkage analysis is a powerful prenatal diagnostic tool in families with unknown genetic defects.

Genome-wide linkage analysis is an established tool to map inherited diseases. To our knowledge it has not been used in prenatal diagnostics of any genetic disorder. We present a family with a severe recessive mental retardation syndrome, where the mother wished pregnancy termination to avoid delivering another affected child. By genome-wide scanning using the Affymetrix (Santa Clara, CA, USA) 10k chip we were able to establish the disease haplotype. Without knowing the exact genetic defect, we excluded the condition in the fetus. The woman finally gave birth to a healthy baby. We suggest that genome-wide linkage analysis--based on either SNP mapping or full-genome sequencing--is a very useful tool in prenatal diagnostics of diseases.