Causative mechanisms and clinical impact of immunoglobulin deficiencies in ataxia telangiectasia.

BACKGROUND: Ataxia telangiectasia (AT) is characterized by cerebellar ataxia, telangiectasia, immunodeficiency, and increased cancer susceptibility and is caused by mutations in the ataxia telangiectasia mutated (ATM) gene. The immunodeficiency comprises predominantly immunoglobulin deficiency, mainly IgA and IgG2, with a variable severity. So far, the exact mechanisms underlying the immunoglobulin deficiency, especially the variable severity, remain unelucidated. OBJECTIVE: We characterized the clinical impact of immunoglobulin deficiencies in AT and elucidated their mechanisms in AT. METHODS: We analyzed long-term immunoglobulin levels, immunophenotyping, and survival time in our cohort (n = 87, median age 16 years; maximum 64 years). Somatic hypermutation and class-switch junctions in B cells were analyzed by next-generation sequencing. Furthermore, an in vitro class-switching induction assay was performed, followed by RNA sequencing, to assess the effect of ATM inhibition. RESULTS: Only the hyper-IgM AT phenotype significantly worsened survival time, while IgA or IgG2 deficiencies did not. The immunoglobulin levels showed predominantly decreased IgG2 and IgA. Moreover, flow cytometric analysis demonstrated reduced naive B and T lymphocytes and a deficiency of class-switched IgG2 and IgA memory B cells. Somatic hypermutation frequencies were lowered in IgA- and IgG2-deficient patients, indicating hampered germinal center reaction. In addition, the microhomology of switch junctions was elongated, suggesting alternative end joining during class-switch DNA repair. The in vitro class switching and proliferation were negatively affected by ATM inhibition. RNA sequencing analysis showed that ATM inhibitor influenced expression of germinal center reaction genes. CONCLUSION: Immunoglobulin deficiency in AT is caused by disturbed development of class-switched memory B cells. ATM deficiency affects both germinal center reaction and choice of DNA-repair pathway in class switching.

CIAO1 and MMS19 deficiency: A lethal neurodegenerative phenotype caused by cytosolic Fe-S cluster protein assembly disorders.

PURPOSE: The functionality of many cellular proteins depends on cofactors; yet, they have only been implicated in a minority of Mendelian diseases. Here, we describe the first 2 inherited disorders of the cytosolic iron-sulfur protein assembly system. METHODS: Genetic testing via genome sequencing was applied to identify the underlying disease cause in 3 patients with microcephaly, congenital brain malformations, progressive developmental and neurologic impairments, recurrent infections, and a fatal outcome. Studies in patient-derived skin fibroblasts and zebrafish models were performed to investigate the biochemical and cellular consequences. RESULTS: Metabolic analysis showed elevated uracil and thymine levels in body fluids but no pathogenic variants in DPYD, encoding dihydropyrimidine dehydrogenase. Genome sequencing identified compound heterozygosity in 2 patients for missense variants in CIAO1, encoding cytosolic iron-sulfur assembly component 1, and homozygosity for an in-frame 3-nucleotide deletion in MMS19, encoding the MMS19 homolog, cytosolic iron-sulfur assembly component, in the third patient. Profound alterations in the proteome, metabolome, and lipidome were observed in patient-derived fibroblasts. We confirmed the detrimental effect of deficiencies in CIAO1 and MMS19 in zebrafish models. CONCLUSION: A general failure of cytosolic and nuclear iron-sulfur protein maturation caused pleiotropic effects. The critical function of the cytosolic iron-sulfur protein assembly machinery for antiviral host defense may well explain the recurrent severe infections occurring in our patients.

Predicting non-response to intraglandular botulinum neurotoxin A injections for drooling in children with neurodevelopmental disabilities.

AIM: To develop robust multivariable prediction models for non-response to (1) submandibular botulinum neurotoxin A (BoNT-A) injections and (2) concurrent submandibular and parotid (four-gland) injections, to guide treatment decisions for drooling in children with neurodevelopmental disabilities, including cerebral palsy. METHOD: This was a retrospective cohort study including 262 children (155 males/107 females, median age 7 years 11 months [IQR 5 years 1 month], range 4 years 0 months - 17 years 11 months) receiving submandibular injections and 74 children (52 males/22 females, median age 7 years 7 months [IQR 4 years 3 months], range 4 years 9 months - 18 years 8 months) receiving four-gland injections. Multivariable logistic regression analyses were used to estimate associations between candidate predictors and non-response 8 weeks after injection. RESULTS: Ninety-six children (37%) were non-responders to submandibular injections, for which developmental age was the strongest predictor (adjusted odds ratio [aOR] 2.13; 95% confidence interval [CI] 1.02-4.45 for developmental age <4 years or 4-6 years with IQ <70). Other characteristics that showed a trend towards an increased risk of non-response were diagnosis, sex, and head position. Thirty-four children (46%) were non-responders to four-gland injections, for which tongue protrusion (aOR 3.10; 95% CI 1.14-8.43) seemed most predictive, whereas multiple preceding submandibular injections (aOR 0.34; 95% CI 0.10-1.16) showed a trend towards being protective. Predictors were, however, unstable across different definitions of non-response and both models (i.e. submandibular and four-gland) had insufficient discriminative ability. INTERPRETATION: Potential predictors of non-response to BoNT-A injections were identified. Nevertheless, the developed prediction models seemed inadequate for guidance of treatment decisions. WHAT THIS PAPER ADDS: Developmental age seemed most predictive of non-response to submandibular botulinum neurotoxin A injections. Non-response to concurrent submandibular and parotid injections was best predicted by tongue protrusion and number of previous injections. Multivariable prediction models including these clinical characteristics were unable to discriminate well. Predictors differed when non-response was defined using alternative outcome measures.

Comparing the evidence for botulinum neurotoxin injections in paediatric anterior drooling: a scoping review.

Paediatric anterior drooling has a major impact on the daily lives of children and caregivers. Intraglandular botulinum neurotoxin type-A (BoNT-A) injections are considered an effective treatment to diminish drooling. However, there is no international consensus on which major salivary glands should be injected to obtain optimal treatment effect while minimizing the risk of side effects. This scoping review aimed to explore the evidence for submandibular BoNT-A injections and concurrent submandibular and parotid (i.e. four-gland) injections, respectively, and assess whether outcomes could be compared across studies to improve decision making regarding the optimal initial BoNT-A treatment approach for paediatric anterior drooling. PubMed, Embase, and Web of Science were searched to identify relevant studies (until October 1, 2023) on submandibular or four-gland BoNT-A injections for the treatment of anterior drooling in children with neurodevelopmental disabilities. Similarities and differences in treatment, patient, outcome, and follow-up characteristics were assessed. Twenty-eight papers were identified; 7 reporting on submandibular injections and 21 on four-gland injections. No major differences in treatment procedures or timing of follow-up were found. However, patient characteristics were poorly reported, there was great variety in outcome measurement, and the assessment of side effects was not clearly described.   Conclusion: This review highlights heterogeneity in outcome measures and patient population descriptors among studies on paediatric BoNT-A injections, limiting the ability to compare treatment effectiveness between submandibular and four-gland injections. These findings emphasize the need for more extensive and uniform reporting of patient characteristics and the implementation of a core outcome measurement set to allow for comparison of results between studies and facilitate the optimization of clinical practice guidelines. What is Known: • There is no international consensus on which salivary glands to initially inject with BoNT-A to treat paediatric drooling. What is New: • Concluding on the optimal initial BoNT-A treatment based on literature is currently infeasible. There is considerable heterogeneity in outcome measures used to quantify anterior drooling.and clinical characteristics of children treated with intraglandular BoNT-A are generally insufficiently reported. • Consensus-based sets of outcome measures and patient characteristics should be developed and implemented.

Child-to-adult transition: a survey of current practices within the European Reference Network for Rare Neurological Diseases (ERN-RND).

BACKGROUND: Transition from child-centered to adult-centered healthcare is a gradual process that addresses the medical, psychological, and educational needs of young people in the management of their autonomy in making decisions about their health and their future clinical assistance. This transfer is challenging across all chronic diseases but can be particularly arduous in rare neurological conditions. AIM: To describe the current practice on the transition process for young patients in centers participating in the European Reference Network for Rare Neurological Diseases (ERN-RND). METHODS: Members of the ERN-RND working group developed a questionnaire considering child-to-adult transition issues and procedures in current clinical practice. The questionnaire included 20 questions and was sent to members of the health care providers (HCPs) participating in the network. RESULTS: Twenty ERN-RND members (75% adult neurologists; 25% pediatricians; 5% nurses or study coordinators) responded to the survey, representing 10 European countries. Transition usually occurs between 16 and 18 years of age, but 55% of pediatric HCPs continue to care for their patients until they reach 40 years of age or older. In 5/20 ERN-RND centers, a standardized procedure managing transition is currently adopted, whereas in the remaining centers, the transition from youth to adult service is usually assisted by pediatricians as part of their clinical practice. CONCLUSIONS: This survey demonstrated significant variations in clinical practice between different centers within the ERN-RND network. It provided valuable data on existing transition programs and highlighted key challenges in managing transitions for patients with rare neurological disorders.

Reframing selection as a learning experience: Insights from a residency selection assessment.

PURPOSE: Selection for postgraduate medical training is high-stakes and complex. The learning value of assessments for selection has, thus far, been underexplored, limiting their uptake as potentially meaningful learning experiences. The aim of this study was to explore the learning value residency applicants derive from an intelligence, personality, motivation and competency selection assessment and what factors influence the experienced learning value. METHODS: In Autumn 2020 and Spring 2021, we conducted individual semi-structured interviews with sixteen applicants for pediatric residency training. Selection outcomes were unknown at the time of the interview. Interviews were transcribed verbatim and thematically analyzed. RESULTS: Participants reported that the assessment was valuable in fostering self-reflection and self-awareness, embracing self-acceptance, pursuing development goals, assessing professional fit, and harnessing motivational drivers in work. The experienced learning value was influenced by applicants' ability to interpret its results, their focus on the high-stakes selection process and concerns regarding the acceptability and credibility of the selection tool. CONCLUSIONS: While the selection assessment showed learning potential, its learning value was impeded by a preoccupation with the high-stakes nature of the selection procedure. Intentional integration of the selection assessment in the learning curriculum may play a pivotal role in realizing its learning potential.

De Novo variants in EEF2 cause a neurodevelopmental disorder with benign external hydrocephalus.

Eukaryotic translation elongation factor 2 (eEF2) is a key regulatory factor in gene expression that catalyzes the elongation stage of translation. A functionally impaired eEF2, due to a heterozygous missense variant in the EEF2 gene, was previously reported in one family with spinocerebellar ataxia-26 (SCA26), an autosomal dominant adult-onset pure cerebellar ataxia. Clinical exome sequencing identified de novo EEF2 variants in three unrelated children presenting with a neurodevelopmental disorder (NDD). Individuals shared a mild phenotype comprising motor delay and relative macrocephaly associated with ventriculomegaly. Populational data and bioinformatic analysis underscored the pathogenicity of all de novo missense variants. The eEF2 yeast model strains demonstrated that patient-derived variants affect cellular growth, sensitivity to translation inhibitors and translational fidelity. Consequently, we propose that pathogenic variants in the EEF2 gene, so far exclusively associated with late-onset SCA26, can cause a broader spectrum of neurologic disorders, including childhood-onset NDDs and benign external hydrocephalus.

Distinguishing Oligosaccharide Isomers Using Far-Infrared Ion Spectroscopy: Identification of Biomarkers for Inborn Errors of Metabolism.

Distinguishing isomeric saccharides poses a major challenge for analytical workflows based on (liquid chromatography) mass spectrometry (LC-MS). In recent years, many studies have proposed infrared ion spectroscopy as a possible solution as the orthogonal, spectroscopic characterization of mass-selected ions can often distinguish isomeric species that remain unresolved using conventional MS. However, the high conformational flexibility and extensive hydrogen bonding in saccharides cause their room-temperature fingerprint infrared spectra to have broad features that often lack diagnostic value. Here, we show that room-temperature infrared spectra of ion-complexed saccharides recorded in the previously unexplored far-infrared wavelength range (300-1000 cm-1) provide well-resolved and highly diagnostic features. We show that this enables distinction of isomeric saccharides that differ either by their composition of monosaccharide units and/or the orientation of their glycosidic linkages. We demonstrate the utility of this approach from single monosaccharides up to isomeric tetrasaccharides differing only by the configuration of a single glycosidic linkage. Furthermore, through hyphenation with hydrophilic interaction liquid chromatography, we identify oligosaccharide biomarkers in patient body fluid samples, demonstrating a generalized and highly sensitive MS-based method for the identification of saccharides found in complex sample matrices.

Heterozygous NOTCH1 Variants Cause CNS Immune Activation and Microangiopathy.

NOTCH1 belongs to the NOTCH family of proteins that regulate cell fate and inflammatory responses. Somatic and germline NOTCH1 variants have been implicated in cancer, Adams-Oliver syndrome, and cardiovascular defects. We describe 7 unrelated patients grouped by the presence of leukoencephalopathy with calcifications and heterozygous de novo gain-of-function variants in NOTCH1. Immunologic profiling showed upregulated CSF IP-10, a cytokine secreted downstream of NOTCH1 signaling. Autopsy revealed extensive leukoencephalopathy and microangiopathy with vascular calcifications. This evidence implicates that heterozygous gain-of-function variants in NOTCH1 lead to a chronic central nervous system (CNS) inflammatory response resulting in a calcifying microangiopathy with leukoencephalopathy. ANN NEUROL 2022;92:895-901.

Gene therapy for aromatic L-amino acid decarboxylase deficiency: Requirements for safe application and knowledge-generating follow-up.

The autosomal recessive defect of aromatic L-amino acid decarboxylase (AADC) leads to a severe neurological disorder with manifestation in infancy due to a pronounced, combined deficiency of dopamine, serotonin and catecholamines. The success of conventional drug treatment is very limited, especially in patients with a severe phenotype. The development of an intracerebral AAV2-based gene delivery targeting the putamen or substantia nigra started more than 10 years ago. Recently, the putaminally-delivered construct, Eladocagene exuparvovec has been approved by the European Medicines Agency and by the British Medicines and Healthcare products Regulatory Agency. This now available gene therapy provides for the first time also for AADC deficiency (AADCD) a causal therapy, leading this disorder into a new therapeutic era. By using a standardized Delphi approach members of the International Working Group on Neurotransmitter related Disorders (iNTD) developed structural requirements and recommendations for the preparation, management and follow-up of AADC deficiency patients who undergo gene therapy. This statement underlines the necessity of a framework for a quality-assured application of AADCD gene therapy including Eladocagene exuparvovec. Treatment requires prehospital, inpatient and posthospital care by a multidisciplinary team in a specialized and qualified therapy center. Due to lack of data on long-term outcomes and the comparative efficacy of alternative stereotactic procedures and brain target sites, a structured follow-up plan and systematic documentation of outcomes in a suitable, industry-independent registry study are necessary.

Novel cerebrospinal fluid biomarkers of glucose transporter type 1 deficiency syndrome: Implications beyond the brain's energy deficit.

We used next-generation metabolic screening to identify new biomarkers for improved diagnosis and pathophysiological understanding of glucose transporter type 1 deficiency syndrome (GLUT1DS), comparing metabolic cerebrospinal fluid (CSF) profiles from 12 patients to those of 116 controls. This confirmed decreased CSF glucose and lactate levels in patients with GLUT1DS and increased glutamine at group level. We identified three novel biomarkers significantly decreased in patients, namely gluconic + galactonic acid, xylose-α1-3-glucose, and xylose-α1-3-xylose-α1-3-glucose, of which the latter two have not previously been identified in body fluids. CSF concentrations of gluconic + galactonic acid may be reduced as these metabolites could serve as alternative substrates for the pentose phosphate pathway. Xylose-α1-3-glucose and xylose-α1-3-xylose-α1-3-glucose may originate from glycosylated proteins; their decreased levels are hypothetically the consequence of insufficient glucose, one of two substrates for O-glucosylation. Since many proteins are O-glucosylated, this deficiency may affect cellular processes and thus contribute to GLUT1DS pathophysiology. The novel CSF biomarkers have the potential to improve the biochemical diagnosis of GLUT1DS. Our findings imply that brain glucose deficiency in GLUT1DS may cause disruptions at the cellular level that go beyond energy metabolism, underlining the importance of developing treatment strategies that directly target cerebral glucose uptake.

Succinic semialdehyde dehydrogenase deficiency in mice and in humans: An untargeted metabolomics perspective.

Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare neurometabolic disorder caused by disruption of the gamma-aminobutyric acid (GABA) pathway. A more detailed understanding of its pathophysiology, beyond the accumulation of GABA and gamma-hydroxybutyric acid (GHB), will increase our understanding of the disease and may support novel therapy development. To this end, we compared biochemical body fluid profiles from SSADHD patients with controls using next-generation metabolic screening (NGMS). Targeted analysis of NGMS data from cerebrospinal fluid (CSF) showed a moderate increase of aspartic acid, glutaric acid, glycolic acid, 4-guanidinobutanoic acid, and 2-hydroxyglutaric acid, and prominent elevations of GHB and 4,5-dihydroxyhexanoic acid (4,5-DHHA) in SSADHD samples. Remarkably, the intensities of 4,5-DHHA and GHB showed a significant positive correlation in control CSF, but not in patient CSF. In an established zebrafish epilepsy model, 4,5-DHHA showed increased mobility that may reflect limited epileptogenesis. Using untargeted metabolomics, we identified 12 features in CSF with high biomarker potential. These had comparable increased fold changes as GHB and 4,5-DHHA. For 10 of these features, a similar increase was found in plasma, urine and/or mouse brain tissue for SSADHD compared to controls. One of these was identified as the novel biomarker 4,5-dihydroxyheptanoic acid. The intensities of selected features in plasma and urine of SSADHD patients positively correlated with the clinical severity score of epilepsy and psychiatric symptoms of those patients, and also showed a high mutual correlation. Our findings provide new insights into the (neuro)metabolic disturbances in SSADHD and give leads for further research concerning SSADHD pathophysiology.

Effects of Sodium Lactate Infusion in Two Girls with Glucose Transporter 1 Deficiency Syndrome.

BACKGROUND: Glucose is an important fuel for the brain. In glucose transporter 1 deficiency syndrome (GLUT1DS), the transport of glucose across the blood-brain barrier is limited. Most individuals with GLUT1DS present with developmental problems, epilepsy, and (paroxysmal) movement disorders, and respond favorably to the ketogenic diet. Similar to ketones, lactate is an alternative energy source for the brain. The aim of this study is to investigate whether intravenous infusion of sodium lactate in children with GLUT1DS has beneficial effects on their epilepsy. METHODS: We performed a proof of principle study with two subjects with GLUT1DS who were not on a ketogenic diet and suffered from absence epilepsy. After overnight fasting, sodium lactate (600 mmol/L) was infused during 120 minutes, under video electroencephalographic (EEG) recording and monitoring of serum lactate, glucose, electrolytes, and pH. Furthermore, the EEGs were compared with pre-/postprandial EEGs of both subjects, obtained shortly before the study. RESULTS: Fasting EEGs of both subjects showed frequent bilateral, frontocentral polyspike and wave complexes. In one subject, no more epileptic discharges were seen postprandially and after the start of lactate infusion. The EEG of the other subject did not change, neither postprandially nor after lactate infusion. Serum pH, lactate, and sodium changed temporarily during the study. CONCLUSION: This study suggests that sodium lactate infusion is possible in individuals with GLUT1DS, and may have potential therapeutic effects. Cellular abnormalities, beyond neuronal energy failure, may contribute to the underlying disease mechanisms of GLUT1DS, explaining why not all individuals respond to the supplementation of alternative energy sources.

Long-term outcomes for females with early-onset dystrophinopathy.

AIM: To study long-term disease course for females with early-onset dystrophinopathy, including common (female) symptoms, challenges in social participation, the need for care, and current healthcare management to support guideline development. METHOD: Twelve females with early-onset dystrophinopathy were followed for a median period of more than 17 years (range 1-36). RESULTS: One patient died owing to end-stage cardiac failure. Cardiac abnormalities were observed in three of the remaining 11 participants. Respiratory function was reduced in seven of 10 participants. Fatigue, myalgia, lower back pain, and arthralgia were reported in more than six of the participants. Functional status varied from exercise intolerance to wheelchair dependency. Most or all of the 10 participants reported restrictions in participation in work (n = 10), household duties (n = 10), sports (n = 9), and education (n = 8). Only a few participants received followed-up pulmonary (n = 2) or rehabilitation (n = 3) care. INTERPRETATION: Females with early-onset dystrophinopathy experience a wide range of impairments, comorbidities, limitations in activities, and restrictions in social participation. The whole spectrum should be acknowledged in the healthcare setting. Neuromuscular and cardiac follow-up are indispensable. Additional respiratory assessment and rehabilitation care are expected to improve health status and support daily activities and participation. WHAT THIS PAPER ADDS: No standard diagnostic procedures seem to exist for female patients suspected for dystrophinopathy. Female participants with early-onset dystrophinopathy experienced a broad scope of burdening symptoms, such as fatigue, myalgia, lower back pain, and arthralgia. None of participants worked full time, all felt restricted in paid work, and most felt restricted in education. Most participants showed decreased lung function, while only one was symptomatic. Availability of rehabilitation care may improve support for daily activities and participation for females with early-onset dystrophinopathy.

The novel P330L pathogenic variant of aromatic amino acid decarboxylase maps on the catalytic flexible loop underlying its crucial role.

Aromatic amino acid decarboxylase (AADC) deficiency is a rare monogenic disease, often fatal in the first decade, causing severe intellectual disability, movement disorders and autonomic dysfunction. It is due to mutations in the gene coding for the AADC enzyme responsible for the synthesis of dopamine and serotonin. Using whole exome sequencing, we have identified a novel homozygous c.989C > T (p.Pro330Leu) variant of AADC causing AADC deficiency. Pro330 is part of an essential structural and functional element: the flexible catalytic loop suggested to cover the active site as a lid and properly position the catalytic residues. Our investigations provide evidence that Pro330 concurs in the achievement of an optimal catalytic competence. Through a combination of bioinformatic approaches, dynamic light scattering measurements, limited proteolysis experiments, spectroscopic and in solution analyses, we demonstrate that the substitution of Pro330 with Leu, although not determining gross conformational changes, results in an enzymatic species that is highly affected in catalysis with a decarboxylase catalytic efficiency decreased by 674- and 194-fold for the two aromatic substrates. This defect does not lead to active site structural disassembling, nor to the inability to bind the pyridoxal 5'-phosphate (PLP) cofactor. The molecular basis for the pathogenic effect of this variant is rather due to a mispositioning of the catalytically competent external aldimine intermediate, as corroborated by spectroscopic analyses and pH dependence of the kinetic parameters. Altogether, we determined the structural basis for the severity of the manifestation of AADC deficiency in this patient and discussed the rationale for a precision therapy.

Bi-allelic GOT2 Mutations Cause a Treatable Malate-Aspartate Shuttle-Related Encephalopathy.

Early-infantile encephalopathies with epilepsy are devastating conditions mandating an accurate diagnosis to guide proper management. Whole-exome sequencing was used to investigate the disease etiology in four children from independent families with intellectual disability and epilepsy, revealing bi-allelic GOT2 mutations. In-depth metabolic studies in individual 1 showed low plasma serine, hypercitrullinemia, hyperlactatemia, and hyperammonemia. The epilepsy was serine and pyridoxine responsive. Functional consequences of observed mutations were tested by measuring enzyme activity and by cell and animal models. Zebrafish and mouse models were used to validate brain developmental and functional defects and to test therapeutic strategies. GOT2 encodes the mitochondrial glutamate oxaloacetate transaminase. GOT2 enzyme activity was deficient in fibroblasts with bi-allelic mutations. GOT2, a member of the malate-aspartate shuttle, plays an essential role in the intracellular NAD(H) redox balance. De novo serine biosynthesis was impaired in fibroblasts with GOT2 mutations and GOT2-knockout HEK293 cells. Correcting the highly oxidized cytosolic NAD-redox state by pyruvate supplementation restored serine biosynthesis in GOT2-deficient cells. Knockdown of got2a in zebrafish resulted in a brain developmental defect associated with seizure-like electroencephalography spikes, which could be rescued by supplying pyridoxine in embryo water. Both pyridoxine and serine synergistically rescued embryonic developmental defects in zebrafish got2a morphants. The two treated individuals reacted favorably to their treatment. Our data provide a mechanistic basis for the biochemical abnormalities in GOT2 deficiency that may also hold for other MAS defects.

How to proceed after "negative" exome: A review on genetic diagnostics, limitations, challenges, and emerging new multiomics techniques.

Exome sequencing (ES) in the clinical setting of inborn metabolic diseases (IMDs) has created tremendous improvement in achieving an accurate and timely molecular diagnosis for a greater number of patients, but it still leaves the majority of patients without a diagnosis. In parallel, (personalized) treatment strategies are increasingly available, but this requires the availability of a molecular diagnosis. IMDs comprise an expanding field with the ongoing identification of novel disease genes and the recognition of multiple inheritance patterns, mosaicism, variable penetrance, and expressivity for known disease genes. The analysis of trio ES is preferred over singleton ES as information on the allelic origin (paternal, maternal, "de novo") reduces the number of variants that require interpretation. All ES data and interpretation strategies should be exploited including CNV and mitochondrial DNA analysis. The constant advancements in available techniques and knowledge necessitate the close exchange of clinicians and molecular geneticists about genotypes and phenotypes, as well as knowledge of the challenges and pitfalls of ES to initiate proper further diagnostic steps. Functional analyses (transcriptomics, proteomics, and metabolomics) can be applied to characterize and validate the impact of identified variants, or to guide the genomic search for a diagnosis in unsolved cases. Future diagnostic techniques (genome sequencing [GS], optical genome mapping, long-read sequencing, and epigenetic profiling) will further enhance the diagnostic yield. We provide an overview of the challenges and limitations inherent to ES followed by an outline of solutions and a clinical checklist, focused on establishing a diagnosis to eventually achieve (personalized) treatment.

Lactate infusion as therapeutical intervention: a scoping review.

Traditionally, clinicians consider lactate as a waste product of anaerobic glycolysis. Interestingly, research has shown that lactate may serve as an alternative fuel for the brain to protect it against harm. The increasing scientific awareness of the potential beneficial side of lactate, however, is entering the clinic rather slowly. Following this, and realizing that the application of potential novel therapeutic strategies in pediatric populations often lags behind the development in adults, this review summarizes the key data on therapeutic use of intravenous infusion of sodium lactate in humans. PubMed and clinicaltrial.gov were searched up until November 2021 focusing on interventional studies in humans. Thirty-four articles were included in this review, with protocols of lactate infusion in adults with diabetes mellitus, traumatic brain injury, Alzheimer's disease, and cardiac disease. One study on lactate infusion in children was also included. Results of our literature search show that sodium lactate can be safely administrated, without major side effects. Additionally, the present literature clearly shows the potential benefits of therapeutic lactate infusion under certain pathological circumstances, including rather common clinical conditions like traumatic brain injury. CONCLUSION: This review shows that lactate is a save, alternative energy source for the adult brain warranting studies on the potential therapeutic effects of sodium lactate infusion in children. WHAT IS KNOWN: • Lactate is generally considered a waste product of anaerobic glycolysis. However, lactate also is an alternative fuel for different organs, including the brain. • Lactate infusion is not incorporated in standard care for any patient population. WHAT IS NEW: • Thirty-four studies investigated the therapeutic use of intravenous sodium lactate in different patient populations, all with different study protocols. • Literature shows that lactate infusion may have beneficial effects in case of hypoglycemia, traumatic brain injury, and cardiac failure without the risk of major side effects.

Parents' experiences with a home-based upper limb training program using a video coaching approach for infants and toddlers with unilateral cerebral palsy: a qualitative interview study.

BACKGROUND: Although early home-based upper limb training programs are promising, in-depth understanding of parents' experiences with these programs is still limited. We developed an early home-based upper limb training program for infants and toddlers (8-36 months) with or at risk of unilateral cerebral palsy using video coaching for parents. The aim of this qualitative study was to evaluate parents' experiences with the home-based training program using a video coaching approach in order to optimize implementation strategies. METHODS: We held semi-structured interviews with parents of 13 children with unilateral cerebral palsy, who participated in our program in the period from 2014 - 2017. On average, parents had delivered two training periods of the program at the time of the interviews. Interviews were analyzed using inductive thematic content analysis. RESULTS: We identified three overarching interacting themes that shaped the experiences of parents with the program: 1) Parental learning comprising the subthemes parents' training competencies and the facilitative and reinforcing role of video coaching, 2) Parental load comprising the subthemes flexibility of the program, supportive network, competing demands, and child's mood and functional capacities, and 3) Parental perseverance comprising the subthemes beliefs and expectancies and seeing child's functional improvements. CONCLUSIONS: For successful implementation of an early home-based upper limb training program using video coaching, support in delivering home-training from a therapist or from others within parents' social network, is needed to relieve parental load. Seeing functional improvements of their child on the videos increased parents' motivation to continue with the training. Positively phrased feedback from an occupational therapist stimulated parents' perseverance and training competency.

Novel Protein Biomarkers of Monoamine Metabolism Defects Correlate with Disease Severity.

BACKGROUND: Genetic defects of monoamine neurotransmitters are rare neurological diseases amenable to treatment with variable response. They are major causes of early parkinsonism and other spectrum of movement disorders including dopa-responsive dystonia. OBJECTIVES: The objective of this study was to conduct proteomic studies in cerebrospinal fluid (CSF) samples of patients with monoamine defects to detect biomarkers involved in pathophysiology, clinical phenotypes, and treatment response. METHODS: A total of 90 patients from diverse centers of the International Working Group on Neurotransmitter Related Disorders were included in the study (37 untreated before CSF collection, 48 treated and 5 unknown at the collection time). Clinical and molecular metadata were related to the protein abundances in the CSF. RESULTS: Concentrations of 4 proteins were significantly altered, detected by mass spectrometry, and confirmed by immunoassays. First, decreased levels of apolipoprotein D were found in severe cases of aromatic L-amino acid decarboxylase deficiency. Second, low levels of apolipoprotein H were observed in patients with the severe phenotype of tyrosine hydroxylase deficiency, whereas increased concentrations of oligodendrocyte myelin glycoprotein were found in the same subset of patients with tyrosine hydroxylase deficiency. Third, decreased levels of collagen6A3 were observed in treated patients with tetrahydrobiopterin deficiency. CONCLUSION: This study with the largest cohort of patients with monoamine defects studied so far reports the proteomic characterization of CSF and identifies 4 novel biomarkers that bring new insights into the consequences of early dopaminergic deprivation in the developing brain. They open new possibilities to understand their role in the pathophysiology of these disorders, and they may serve as potential predictors of disease severity and therapies. © 2020 International Parkinson and Movement Disorder Society.