Newborn screening for aromatic l-amino acid decarboxylase deficiency - Strategies, results, and implication for prevalence calculations.

BACKGROUND: Aromatic l-amino acid decarboxylase deficiency (AADCD) is a rare, autosomal-recessive neurometabolic disorder caused by variants in dopa decarboxylase (DDC) gene, resulting in a severe combined deficiency of serotonin, dopamine, norepinephrine, and epinephrine. Birth prevalence of AADCD varies by population. In pilot studies, 3-O-methyldopa (3-OMD) was shown to be a reliable biomarker for AADCD in high-throughput newborn screening (NBS) allowing an early diagnosis and access to gene therapy. To evaluate the usefulness of this method for routine NBS, 3-OMD screening results from the largest three German NBS centers were analyzed. METHODS: A prospective, multicenter (n = 3) NBS pilot study evaluated screening for AADCD by quantifying 3-OMD in dried blood spots (DBS) using tandem mass spectrometry (MS/MS). RESULTS: In total, 766,660 neonates were screened from January 2021 until June 2023 with 766,647 with unremarkable AADCD NBS (766,443 by 1st-tier analysis and 204 by 2nd-tier analysis) and 13 with positive NBS result recalled for confirmatory diagnostics (recall-rate about 1:59,000). Molecular genetic analysis confirmed AADCD (c.79C > T p.[Arg27Cys] in Exon 2 und c.215 A > C p.[His72Pro] in Exon 3) in one infant. Another individual was highly suspected with AADCD but died before confirmation (overall positive predictive value 0.15). False-positive results were caused by maternal L-Dopa use (n = 2) and prematurity (30th and 36th week of gestation, n = 2). However, in 63% (n = 7) the underlying etiology for false positive results remained unexplained. Estimated birth prevalence (95% confidence interval) was 1:766,660 (95% CI 1:775,194; 1:769,231) to 1:383,330 (95% CI 1:384,615; 1:383,142). The identified child remained asymptomatic until last follow up at the age of 9 months. CONCLUSIONS: The proposed screening strategy with 3-OMD detection in DBS is feasible and effective to identify individuals with AADCD. The estimated birth prevalence supports earlier estimations and confirms AADCD as a very rare disorder. Pre-symptomatic identification by NBS allows a disease severity adapted drug support to diminish clinical complications until individuals are old enough for the application of the gene therapy.

Comparative analysis of gene and disease selection in genomic newborn screening studies.

Genomic newborn screening (gNBS) is on the horizon given the decreasing costs of sequencing and the advanced understanding of the impact of genetic variants on health and diseases. Key to ongoing gNBS pilot studies is the selection of target diseases and associated genes to be included. In this study, we present a comprehensive analysis of seven published gene-disease lists from gNBS studies, evaluating gene-disease count, composition, group proportions, and ClinGen curations of individual disorders. Despite shared selection criteria, we observe substantial variation in total gene count (median 480, range 237-889) and disease group composition. An intersection was identified for 53 genes, primarily inherited metabolic diseases (83%, 44/53). Each study investigated a subset of exclusive gene-disease pairs, and the total number of exclusive gene-disease pairs was positively correlated with the total number of genes included per study. While most pairs receive "Definitive" or "Strong" ClinGen classifications, some are labeled as "Refuted" (n = 5) or "Disputed" (n = 28), particularly in genetic cardiac diseases. Importantly, 17%-48% of genes lack ClinGen curation. This study underscores the current absence of consensus recommendations for selection criteria for target diseases for gNBS resulting in diversity in proposed gene-disease pairs, their coupling with gene variations and the use of ClinGen curation. Our findings provide crucial insights into the selection of target diseases and accompanying gene variations for future gNBS program, emphasizing the necessity for ongoing collaboration and discussion about criteria harmonization for panel selection to ensure the screening's objectivity, integrity, and broad acceptance.

Outcomes after newborn screening for propionic and methylmalonic acidemia and homocystinurias.

The current German newborn screening (NBS) panel includes 13 inherited metabolic diseases (IMDs). In addition, a NBS pilot study in Southwest Germany identifies individuals with propionic acidemia (PA), methylmalonic acidemia (MMA), combined and isolated remethylation disorders (e.g., cobalamin [cbl] C and methylenetetrahydrofolate reductase [MTHFR] deficiency), cystathionine ß-synthase (CBS) deficiency, and neonatal cbl deficiency through one multiple-tier algorithm. The long-term health benefits of screened individuals are evaluated in a multicenter observational study. Twenty seven screened individuals with IMDs (PA [N = 13], MMA [N = 6], cblC deficiency [N = 5], MTHFR deficiency [N = 2] and CBS deficiency [N = 1]), and 42 with neonatal cbl deficiency were followed for a median of 3.6 years. Seventeen screened IMD patients (63%) experienced at least one metabolic decompensation, 14 of them neonatally and six even before the NBS report (PA, cbl-nonresponsive MMA). Three PA patients died despite NBS and immediate treatment. Fifteen individuals (79%) with PA or MMA and all with cblC deficiency developed permanent, mostly neurological symptoms, while individuals with MTHFR, CBS, and neonatal cbl deficiency had a favorable clinical outcome. Utilizing a combined multiple-tier algorithm, we demonstrate that NBS and specialized metabolic care result in substantial benefits for individuals with MTHFR deficiency, CBS deficiency, neonatal cbl deficiency, and to some extent, cbl-responsive MMA and cblC deficiency. However, its advantage is less evident for individuals with PA and cbl-nonresponsive MMA. SYNOPSIS: Early detection through newborn screening and subsequent specialized metabolic care improve clinical outcomes and survival in individuals with MTHFR deficiency and cystathionine-ß-synthase deficiency, and to some extent in cobalamin-responsive methylmalonic acidemia (MMA) and cblC deficiency while the benefit for individuals with propionic acidemia and cobalamin-nonresponsive MMA is less evident due to the high (neonatal) decompensation rate, mortality, and long-term complications.

Long-term anthropometric development of individuals with inherited metabolic diseases identified by newborn screening.

Newborn screening (NBS) for inherited metabolic diseases (IMDs) substantially shortens a patient's journey. It enables the early start of metabolic treatment which might prevent potentially lethal neonatal disease manifestations, while promoting favorable development and long-term clinical outcomes. This study aims to assess growth in screened individuals with IMDs under different dietary regimes. Anthropometric data (3585 prospective measures) of 350 screened individuals with IMDs born between 1999 and 2018 and participating in a German prospective multicenter observational study were evaluated. Overall, birth measures were within the reference ranges, suggesting unaffected prenatal growth, except for phenylketonuria (weight) and glutaric aciduria Type 1 (head circumference). After birth, longitudinal analysis of anthropometric measures revealed a loss of height standard deviation score (SDS; -0.5 SDS; p < 0.0001), head circumference SDS (-0.2 SDS; p = 0.0028), but not for weight SDS (0.1 SDS; p = 0.5097) until the age of 18 years, while BMI SDS increased (0.4 SDS; p < 0.0001). The significant interaction with age and diet groups was pronounced for the linear growth in individuals receiving diets being low in protein, long-chain triglycerides, and galactose (p < 0.001). Identification by NBS and subsequent early (dietary) treatment cannot completely protect against alterations in growths. Disease-specific (e.g., metabolic impairments, neurotoxins) and dietary-specific (e.g., diets reduced in protein) factors may have an amplified impact on longitudinal growth. Therefore, alongside other important follow-ups, the continuous observation of the anthropometric development of screened individuals with IMDs needs special attention to early identify and support individuals at risk.

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.

Impact of the SARS-CoV-2 pandemic on the health of individuals with intoxication-type metabolic diseases-Data from the E-IMD consortium.

The SARS-CoV-2 pandemic challenges healthcare systems worldwide. Within inherited metabolic disorders (IMDs) the vulnerable subgroup of intoxication-type IMDs such as organic acidurias (OA) and urea cycle disorders (UCD) show risk for infection-induced morbidity and mortality. This study (observation period February 2020 to December 2021) evaluates impact on medical health care as well as disease course and outcome of SARS-CoV-2 infections in patients with intoxication-type IMDs managed by participants of the European Registry and Network for intoxication type metabolic diseases Consortium (E-IMD). Survey's respondents managing 792 patients (n = 479 pediatric; n = 313 adult) with intoxication-type IMDs (n = 454 OA; n = 338 UCD) in 14 countries reported on 59 (OA: n = 36; UCD: n = 23), SARS-CoV-2 infections (7.4%). Medical services were increasingly requested (95%), mostly alleviated by remote technologies (86%). Problems with medical supply were scarce (5%). Regular follow-up visits were reduced in 41% (range 10%-50%). Most infected individuals (49/59; 83%) showed mild clinical symptoms, while 10 patients (17%; n = 6 OA including four transplanted MMA patients; n = 4 UCD) were hospitalized (metabolic decompensation in 30%). ICU treatment was not reported. Hospitalization rate did not differ for diagnosis or age group (p = 0.778). Survival rate was 100%. Full recovery was reported for 100% in outpatient care and 90% of hospitalized individuals. SARS-CoV-2 impacts health care of individuals with intoxication-type IMDs worldwide. Most infected individuals, however, showed mild symptoms and did not require hospitalization. SARS-CoV-2-induced metabolic decompensations were usually mild without increased risk for ICU treatment. Overall prognosis of infected individuals is very promising and IMD-specific or COVID-19-related complications have not been observed.

Collaborative evaluation study on 18 candidate diseases for newborn screening in 1.77 million samples.

Analytical and therapeutic innovations led to a continuous but variable extension of newborn screening (NBS) programmes worldwide. Every extension requires a careful evaluation of feasibility, diagnostic (process) quality and possible health benefits to balance benefits and limitations. The aim of this study was to evaluate the suitability of 18 candidate diseases for inclusion in NBS programmes. Utilising tandem mass spectrometry as well as establishing specific diagnostic pathways with second-tier analyses, three German NBS centres designed and conducted an evaluation study for 18 candidate diseases, all of them inherited metabolic diseases. In total, 1 777 264 NBS samples were analysed. Overall, 441 positive NBS results were reported resulting in 68 confirmed diagnoses, 373 false-positive cases and an estimated cumulative prevalence of approximately 1 in 26 000 newborns. The positive predictive value ranged from 0.07 (carnitine transporter defect) to 0.67 (HMG-CoA lyase deficiency). Three individuals were missed and 14 individuals (21%) developed symptoms before the positive NBS results were reported. The majority of tested candidate diseases were found to be suitable for inclusion in NBS programmes, while multiple acyl-CoA dehydrogenase deficiency, isolated methylmalonic acidurias, propionic acidemia and malonyl-CoA decarboxylase deficiency showed some and carnitine transporter defect significant limitations. Evaluation studies are an important tool to assess the potential benefits and limitations of expanding NBS programmes to new diseases.

[Evaluation and optimization of newborn screening by structured long-term follow-up-using the example of inherited metabolic diseases]. / Evaluierung und Optimierung des Neugeborenenscreenings mittels strukturierter Langzeitbeobachtung ­ am Beispiel der angeborenen Stoffwechselerkrankungen.

Newborn screening (NBS) is a highly successful secondary prevention program with the goal of preventing severe sequelae of congenital, mostly genetic, diseases by identifying them as early as possible, ideally in the pre-symptomatic period. Studies to date have shown the important achievements of NBS programs but also reveal a number of relevant weaknesses. These include the often incompletely understood natural history and phenotypic diversity of rare diseases as well as the inadequate ability to accurately predict individual disease severity at an early stage and thus the uncertainties in case definition, risk stratification, and treatment indication.In light of the rapid developments in high-throughput genetic technologies and the associated opportunities for substantial future expansion of NBS programs, it seems overdue to make structured long-term follow-up and the subsequent evaluation of the long-term health benefits mandatory for individuals with rare diseases identified through NBS. This article explains the importance of long-term follow-up for the evaluation and continuous optimization of the screening. Long-term clinical outcomes of people with inherited metabolic diseases identified by NBS are presented as examples.

How longitudinal observational studies can guide screening strategy for rare diseases.

Newborn screening (NBS) is an important secondary prevention program, aiming to shift the paradigm of medicine to the pre-clinical stage of a disease. Starting more than 50 years ago, technical advances, such as tandem mass spectrometry (MS/MS), paved the way to a continuous extension of NBS programs. However, formal evidence of the long-term clinical benefits in large cohorts and cost-effectiveness of extended NBS programs is still scarce. Although published studies confirmed important benefits of NBS programs, it also unraveled a significant number of limitations. These include an incompletely understood natural history and phenotypic diversity of some screened diseases, unreliable early and precise prediction of individual disease severity, uncertainty about case definition, risk stratification, and indication to treat, resulting in a diagnostic and treatment dilemma in individuals with ambiguous screening and confirmatory test results. Interoperable patient registries are multi-purpose tools that could help to close the current knowledge gaps and to inform further optimization of NBS strategy. Standing at the edge of introducing high throughput genetic technologies to NBS programs with the opportunity to massively extend NBS programs and with the risk of aggravating current limitations of NBS programs, it seems overdue to include mandatory long-term follow-up of NBS cohorts into the list of screening principles and to build an international collaborative framework that enables data collection and exchange in a protected environment, integrating the perspectives of patients, families, and the society.

Postauthorization safety study of betaine anhydrous.

Patient registries for rare diseases enable systematic data collection and can also be used to facilitate postauthorization safety studies (PASS) for orphan drugs. This study evaluates the PASS for betaine anhydrous (Cystadane), conducted as public private partnership (PPP) between the European network and registry for homocystinurias and methylation defects and the marketing authorization holder (MAH). Data were prospectively collected, 2013-2016, in a noninterventional, international, multicenter, registry study. Putative adverse and severe adverse events were reported to the MAH's pharmacovigilance. In total, 130 individuals with vitamin B6 nonresponsive (N = 54) and partially responsive (N = 7) cystathionine beta-synthase (CBS) deficiency, as well as 5,10-methylenetetrahydrofolate reductase (MTHFR; N = 21) deficiency and cobalamin C (N = 48) disease were included. Median (range) duration of treatment with betaine anhydrous was 6.8 (0-9.8) years. The prescribed betaine dose exceeded the recommended maximum (6 g/day) in 49% of individuals older than 10 years because of continued dose adaptation to weight; however, with disease-specific differences (minimum: 31% in B6 nonresponsive CBS deficiency, maximum: 67% in MTHFR deficiency). Despite dose escalation no new or potential risk was identified. Combined disease-specific treatment decreased mean ± SD total plasma homocysteine concentrations from 203 ± 116 to 81 ± 51 µmol/L (p < 0.0001), except in MTHFR deficiency. Recommendations for betaine anhydrous dosage were revised for individuals ≥ 10 years. PPPs between MAH and international scientific consortia can be considered a reliable model for implementing a PASS, reutilizing well-established structures and avoiding data duplication and fragmentation.

Impact of pregnancy planning and preconceptual dietary training on metabolic control and offspring's outcome in phenylketonuria.

To prevent maternal phenylketonuria (PKU) syndrome low phenylalanine concentrations (target range, 120-360 µmol/L) during pregnancy are recommended for women with PKU. We evaluated the feasibility and effectiveness of current recommendations and identified factors influencing maternal metabolic control and children's outcome. Retrospective study of first successfully completed pregnancies of 85 women with PKU from 12 German centers using historical data and interviews with the women. Children's outcome was evaluated by standardized IQ tests and parental rating of child behavior. Seventy-four percent (63/85) of women started treatment before conception, 64% (54/85) reached the phenylalanine target range before conception. Pregnancy planning resulted in earlier achievement of the phenylalanine target (18 weeks before conception planned vs. 11 weeks of gestation unplanned, p < 0.001) and lower plasma phenylalanine concentrations during pregnancy, particularly in the first trimester (0-7 weeks of gestation: 247 µmol/L planned vs. 467 µmol/L unplanned, p < 0.0001; 8-12 weeks of gestation: 235 µmol/L planned vs. 414 µmol/L unplanned, p < 0.001). Preconceptual dietary training increased the success rate of achieving the phenylalanine target before conception compared to women without training (19 weeks before conception vs. 9 weeks of gestation, p < 0.001). The majority (93%) of children had normal IQ (mean 103, median age 7.3 years); however, IQ decreased with increasing phenylalanine concentration during pregnancy. Good metabolic control during pregnancy is the prerequisite to prevent maternal PKU syndrome in the offspring. This can be achieved by timely provision of detailed information, preconceptual dietary training, and careful planning of pregnancy.

Sudden neonatal death in individuals with medium-chain acyl-coenzyme A dehydrogenase deficiency: limit of newborn screening.

Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency is the most common disorder of mitochondrial ß-oxidation of fatty acids resulting in hypoketotic hypoglycemia, hepatopathy, and often fatal outcome in undiagnosed children. Introduction of tandem mass spectrometry-based newborn screening programs in the late 1990s has significantly reduced morbidity and mortality in MCAD deficiency; however, neonatal death in individuals with early disease manifestation and severe hypoglycemia may still occur. We describe the fatal disease course in eight newborns with MCAD deficiency, aiming to raise awareness for early clinical symptoms and the life-saving treatment, and promote systematic post-mortem protocols for biochemical and genetic testing, necessary for correct diagnosis and counselling of the family if unexpected death occurred in the neonatal period.Conclusion: Early newborn screening and awareness for clinical symptoms is lifesaving in MCAD deficiency, which may present with fatal neonatal crisis. Systematic post-mortem diagnostic protocols are needed for sudden neonatal deaths.

Health Outcomes of Infants with Vitamin B12 Deficiency Identified by Newborn Screening and Early Treated.

OBJECTIVE: To evaluate the clinical outcomes at age 1.5 ± 0.5 years of infants with vitamin B12 deficiency identified by newborn screening (NBS). STUDY DESIGN: Prospective multicenter observational study on health outcomes of 31 infants with vitamin B12 deficiency identified by NBS. Neurodevelopment was assessed by the Denver Developmental Screening Test. RESULTS: In 285 862 newborns screened between 2016 and 2019, the estimated birth prevalence of vitamin B12 deficiency was 26 in 100 000 newborns, with high seasonal variations (lowest in summer: 8 in 100 000). Infants participating in the outcome study (N = 31) were supplemented with vitamin B12 for a median (range) of 5.9 (1.1-16.2) months. All achieved age-appropriate test results in Denver Developmental Screening Test at age 15 (11-23) months and did not present with symptoms characteristic for vitamin B12 deficiency. Most (81%, n = 25) mothers of affected newborns had a hitherto undiagnosed (functional) vitamin B12 deficiency, and, subsequently, received specific therapy. CONCLUSIONS: Neonatal vitamin B12 deficiency can be screened by NBS, preventing the manifestation of irreversible neurologic symptoms and the recurrence of vitamin B12 deficiency in future pregnancies through adequate treatment of affected newborns and their mothers. The high frequency of mothers with migrant background having a newborn with vitamin B12 deficiency highlights the need for improved prenatal care.

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.

Newborn Screening for Vitamin B12 Deficiency in Germany-Strategies, Results, and Public Health Implications.

OBJECTIVE: To evaluate a systematic newborn screening (NBS) strategy for vitamin B12 deficiency. STUDY DESIGN: In a prospective single-center NBS study, a systematic screening strategy for vitamin B12 deficiency was developed and evaluated. Tandem-mass spectrometry screening was complemented by 2 second-tier strategies, measuring methylmalonic/3-OH-propionic/methylcitric acid, and homocysteine from dried blood spots. RESULTS: In a cohort of 176 702 children screened over 27 months, 33 children were detected by NBS in whom (maternal) vitamin B12 deficiency was confirmed. Homocysteine was the most sensitive marker for vitamin B12 deficiency, but only combination with a second-tier strategy evaluating methylmalonic acid allowed for detection of all 33 children. Mothers were of various ethnic origins, and 89% adhered to a balanced diet. Treatment in children was performed predominantly by oral vitamin B12 supplementation (84%), and all children remained without clinical symptoms at short-term follow-up. CONCLUSIONS: Vitamin B12 deficiency is a treatable condition but can cause severe neurologic sequelae in infants if untreated. The proposed screening strategy is feasible and effective to identify moderate and severe cases of vitamin B12 deficiency. With an incidence of 1:5355 newborns, vitamin B12 deficiency is more frequent than inborn errors of metabolism included in NBS panels. Treatment of vitamin B12 deficiency is easy, and additional benefits can be achieved for previously undiagnosed affected mothers. This supports inclusion of vitamin B12 deficiency into NBS but also stresses the need for increased awareness of vitamin B12 deficiency in caregivers of pregnant women.

Organic acidurias in adults: late complications and management.

Organic acidurias (synonym, organic acid disorders, OADs) are a heterogenous group of inherited metabolic diseases delineated with the implementation of gas chromatography/mass spectrometry in metabolic laboratories starting in the 1960s and 1970s. Biochemically, OADs are characterized by accumulation of mono-, di- and/or tricarboxylic acids ("organic acids") and corresponding coenzyme A, carnitine and/or glycine esters, some of which are considered toxic at high concentrations. Clinically, disease onset is variable, however, affected individuals may already present during the newborn period with life-threatening acute metabolic crises and acute multi-organ failure. Tandem mass spectrometry-based newborn screening programmes, in particular for isovaleric aciduria and glutaric aciduria type 1, have significantly reduced diagnostic delay. Dietary treatment with low protein intake or reduced intake of the precursor amino acid(s), carnitine supplementation, cofactor treatment (in responsive patients) and nonadsorbable antibiotics is commonly used for maintenance treatment. Emergency treatment options with high carbohydrate/glucose intake, pharmacological and extracorporeal detoxification of accumulating toxic metabolites for intensified therapy during threatening episodes exist. Diagnostic and therapeutic measures have improved survival and overall outcome in individuals with OADs. However, it has become increasingly evident that the manifestation of late disease complications cannot be reliably predicted and prevented. Conventional metabolic treatment often fails to prevent irreversible organ dysfunction with increasing age, even if patients are considered to be "metabolically stable". This has challenged our understanding of OADs and has elicited the discussion on optimized therapy, including (early) organ transplantation, and long-term care.

Delineating SPTAN1 associated phenotypes: from isolated epilepsy to encephalopathy with progressive brain atrophy.

De novo in-frame deletions and duplications in the SPTAN1 gene, encoding the non-erythrocyte αII spectrin, have been associated with severe West syndrome with hypomyelination and pontocerebellar atrophy. We aimed at comprehensively delineating the phenotypic spectrum associated with SPTAN1 mutations. Using different molecular genetic techniques, we identified 20 patients with a pathogenic or likely pathogenic SPTAN1 variant and reviewed their clinical, genetic and imaging data. SPTAN1 de novo alterations included seven unique missense variants and nine in-frame deletions/duplications of which 12 were novel. The recurrent three-amino acid duplication p.(Asp2303_Leu2305dup) occurred in five patients. Our patient cohort exhibited a broad spectrum of neurodevelopmental phenotypes, comprising six patients with mild to moderate intellectual disability, with or without epilepsy and behavioural disorders, and 14 patients with infantile epileptic encephalopathy, of which 13 had severe neurodevelopmental impairment and four died in early childhood. Imaging studies suggested that the severity of neurological impairment and epilepsy correlates with that of structural abnormalities as well as the mutation type and location. Out of seven patients harbouring mutations outside the α/ß spectrin heterodimerization domain, four had normal brain imaging and three exhibited moderately progressive brain and/or cerebellar atrophy. Twelve of 13 patients with mutations located within the spectrin heterodimer contact site exhibited severe and progressive brain, brainstem and cerebellar atrophy, with hypomyelination in most. We used fibroblasts from five patients to study spectrin aggregate formation by Triton-X extraction and immunocytochemistry followed by fluorescence microscopy. αII/ßII aggregates and αII spectrin in the insoluble protein fraction were observed in fibroblasts derived from patients with the mutations p.(Glu2207del), p.(Asp2303_Leu2305dup) and p.(Arg2308_Met2309dup), all falling in the nucleation site of the α/ß spectrin heterodimer region. Molecular modelling of the seven SPTAN1 amino acid changes provided preliminary evidence for structural alterations of the A-, B- and/or C-helices within each of the mutated spectrin repeats. We conclude that SPTAN1-related disorders comprise a wide spectrum of neurodevelopmental phenotypes ranging from mild to severe and progressive. Spectrin aggregate formation in fibroblasts with mutations in the α/ß heterodimerization domain seems to be associated with a severe neurodegenerative course and suggests that the amino acid stretch from Asp2303 to Met2309 in the α20 repeat is important for α/ß spectrin heterodimer formation and/or αII spectrin function.

Personalized metabolic whole-body models for newborns and infants predict growth and biomarkers of inherited metabolic diseases.

Comprehensive whole-body models (WBMs) accounting for organ-specific dynamics have been developed to simulate adult metabolism, but such models do not exist for infants. Here, we present a resource of 360 organ-resolved, sex-specific models of newborn and infant metabolism (infant-WBMs) spanning the first 180 days of life. These infant-WBMs were parameterized to represent the distinct metabolic characteristics of newborns and infants, including nutrition, energy requirements, and thermoregulation. We demonstrate that the predicted infant growth was consistent with the recommendation by the World Health Organization. We assessed the infant-WBMs' reliability and capabilities for personalization by simulating 10,000 newborns based on their blood metabolome and birth weight. Furthermore, the infant-WBMs accurately predicted changes in known biomarkers over time and metabolic responses to treatment strategies for inherited metabolic diseases. The infant-WBM resource holds promise for personalized medicine, as the infant-WBMs could be a first step to digital metabolic twins for newborn and infant metabolism.

Treatment Outcomes for Maple Syrup Urine Disease Detected by Newborn Screening.

OBJECTIVE: Maple syrup urine disease (MSUD), a life-threatening metabolic disorder, is included in newborn screening (NBS) programs worldwide. The study aims to evaluate the impact of NBS on the long-term outcome of MSUD patients. METHODS: We performed a prospective, national, multicenter, observational study. RESULTS: In the studied NBS cohort (N = 33; 22 classic MSUD [cMSUD], 11 variant MSUD [vMSUD]; median age at last visit 10.4 years), 32 (97%) patients survived, 58% of them had normal cognitive functions (median IQ 87). Initial peak leucine increased linearly with age in cMSUD (median: 1712 µmol/L), but not in vMSUD. Global IQ correlated inversely with the initial peak leucine concentration (P = .04; ß = -0.0081) and the frequency of decompensations (P = .02; ß = -9.133). A cluster analysis identified 2 subgroups differing in their long-term metabolic control (median leucine concentration: 162 vs 278 µmol/L; P < .001). In cMSUD, lower leucine concentrations were associated with a higher IQ (95.5 vs 80; P = .008). Liver transplantation (median age 5.8 years) was not associated with better cognitive outcome. NBS is highly sensitive for cMSUD, but vMSUD might be missed (N = 2 missed by NBS). CONCLUSIONS: NBS and the early start of treatment improve survival and long-term outcome in individuals with cMSUD. Disease severity is an important modifier of outcome; however, the time to NBS report and the quality of long-term metabolic control had an independent impact on cognitive outcome, highlighting the importance of an early diagnosis and the quality of treatment.

Neurological outcome in long-chain hydroxy fatty acid oxidation disorders.

OBJECTIVE: This study aims to elucidate the long-term benefit of newborn screening (NBS) for individuals with long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiency, inherited metabolic diseases included in NBS programs worldwide. METHODS: German national multicenter study of individuals with confirmed LCHAD/MTP deficiency identified by NBS between 1999 and 2020 or selective metabolic screening. Analyses focused on NBS results, confirmatory diagnostics, and long-term clinical outcomes. RESULTS: Sixty-seven individuals with LCHAD/MTP deficiency were included in the study, thereof 54 identified by NBS. All screened individuals with LCHAD deficiency survived, but four with MTP deficiency (14.8%) died during the study period. Despite NBS and early treatment neonatal decompensations (28%), symptomatic disease course (94%), later metabolic decompensations (80%), cardiomyopathy (28%), myopathy (82%), hepatopathy (32%), retinopathy (17%), and/or neuropathy (22%) occurred. Hospitalization rates were high (up to a mean of 2.4 times/year). Disease courses in screened individuals with LCHAD and MTP deficiency were similar except for neuropathy, occurring earlier in individuals with MTP deficiency (median 3.9 vs. 11.4 years; p = 0.0447). Achievement of dietary goals decreased with age, from 75% in the first year of life to 12% at age 10, and consensus group recommendations on dietary management were often not achieved. INTERPRETATION: While NBS and early treatment result in improved (neonatal) survival, they cannot reliably prevent long-term morbidity in screened individuals with LCHAD/MTP deficiency, highlighting the urgent need of better therapeutic strategies and the development of disease course-altering treatment.