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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 β‐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‐β‐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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase gene. Depending on the severity of the genetic mutation, medical treatment, and patient dietary management, elevated phenylalanine (Phe) may occur in blood and brain tissues. Research has recently shown that high Phe not only impacts the central nervous system, but also other organ systems (e.g., heart and microbiome). This study used ex vivo proton nuclear magnetic resonance (1H-NMR) analysis of urine samples from PKU patients (mean 14.9 ± 9.2 years, n = 51) to identify the impact of elevated blood Phe and PKU treatment on metabolic profiles. Our results found that 24 out of 98 urinary metabolites showed a significant difference (p < 0.05) for PKU patients compared to age-matched healthy controls (n = 51) based on an analysis of urinary metabolome. These altered urinary metabolites were related to Phe metabolism, dysbiosis, creatine synthesis or intake, the tricarboxylic acid (TCA) cycle, end products of nicotinamide-adenine dinucleotide degradation, and metabolites associated with a low Phe diet. There was an excellent correlation between the metabolome and genotype of PKU patients and healthy controls of 96.7% in a confusion matrix model. Metabolomic investigations may contribute to a better understanding of PKU pathophysiology. [ABSTRACT FROM AUTHOR]

There are about 1500 genetic metabolic diseases. A small number of treatable diseases are diagnosed by newborn screening programs, which are continually being developed. However, most diseases can only be diagnosed based on clinical symptoms or metabolic findings. The main biological fluids used are urine, plasma and, in special situations, cerebrospinal fluid. In contrast to commonly used methods such as gas chromatography and high performance liquid chromatography mass spectrometry, ex vivo proton spectroscopy (1H‐NMR) is not yet used in routine clinical practice, although it has been recommended for more than 30 years. Automatic analysis and improved NMR technology have also expanded the applications used for the diagnosis of inborn errors of metabolism. We provide a mini‐overview of typical applications, especially in urine but also in plasma, used to diagnose common but also rare genetic metabolic diseases with 1H‐NMR. The use of computer‐assisted diagnostic suggestions can facilitate interpretation of the profiles. In a proof of principle, to date, 182 reports of 59 different diseases and 500 reports of healthy children are stored. The percentage of correct automatic diagnoses was 74%. Using the same 1H‐NMR profile‐targeted analysis, it is possible to apply an untargeted approach that distinguishes profile differences from healthy individuals. Thus, additional conditions such as lysosomal storage diseases or drug interferences are detectable. Furthermore, because 1H‐NMR is highly reproducible and can detect a variety of different substance categories, the metabolomic approach is suitable for monitoring patient treatment and revealing additional factors such as nutrition and microbiome metabolism. Besides the progress in analytical techniques, a multiomics approach is most effective to combine metabolomics with, for example, whole exome sequencing, to also diagnose patients with nondetectable metabolic abnormalities in biological fluids. In this mini review we also provide our own data to demonstrate the role of NMR in a multiomics platform in the field of inborn errors of metabolism. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The mitochondrial malate aspartate shuttle system (MAS) maintains the cytosolic NAD+/NADH redox balance, thereby sustaining cytosolic redox-dependent pathways, such as glycolysis and serine biosynthesis. Human disease has been associated with defects in four MAS-proteins (encoded by MDH1, MDH2, GOT2, SLC25A12) sharing a neurological/epileptic phenotype, as well as citrin deficiency (SLC25A13) with a complex hepatopathic-neuropsychiatric phenotype. Ketogenic diets (KD) are high-fat/low-carbohydrate diets, which decrease glycolysis thus bypassing the mentioned defects. The same holds for mitochondrial pyruvate carrier (MPC) 1 deficiency, which also presents neurological deficits. We here describe 40 (18 previously unreported) subjects with MAS-/MPC1-defects (32 neurological phenotypes, eight citrin deficiency), describe and discuss their phenotypes and genotypes (presenting 12 novel variants), and the efficacy of KD. Of 13 MAS/MPC1-individuals with a neurological phenotype treated with KD, 11 experienced benefits—mainly a striking effect against seizures. Two individuals with citrin deficiency deceased before the correct diagnosis was established, presumably due to high-carbohydrate treatment. Six citrin-deficient individuals received a carbohydrate-restricted/fat-enriched diet and showed normalisation of laboratory values/hepatopathy as well as age-adequate thriving. We conclude that patients with MAS-/MPC1-defects are amenable to dietary intervention and that early (genetic) diagnosis is key for initiation of proper treatment and can even be lifesaving. [ABSTRACT FROM AUTHOR]

Methionine adenosyltransferase I/III deficiency is an inborn error of metabolism due to mutations in the MAT1A gene. It is the most common cause of hypermethioninemia in newborn screening. Heterozygotes are often asymptomatic. In contrast, homozygous or compound heterozygous individuals can develop severe neurological symptoms. Less than 70 cases with biallelic variants have been reported worldwide. A methionine-restricted diet is recommended if methionine levels are above 500–600 µmol/L. In this study, we report on a female patient identified with elevated methionine concentrations in a pilot newborn screening program. The patient carries a previously described variant c.1132G>A (p.Gly378Ser) in homozygosity. It is located at the C-terminus of MAT1A. In silico analysis suggests impaired protein stability by β-turn disruption. On a methionine-restricted diet, her serum methionine concentration ranged between 49–605 µmol/L (median 358 µmol/L). Her clinical course was characterized by early-onset muscular hypotonia, mild developmental delay, delayed myelination and mild periventricular diffusion interference in MRI. At 21 months, the girl showed age-appropriate neurological development, but progressive diffusion disturbances in MRI. Little is known about the long-term outcome of this disorder and the necessity of treatment. Our case demonstrates that neurological symptoms can be transient and even patients with initial neurologic manifestations can show normal development under dietary management. [ABSTRACT FROM AUTHOR]

The recent description of biallelic DNAJC30 variants in Leber hereditary optic neuropathy (LHON) and Leigh syndrome challenged the longstanding assumption for LHON to be exclusively maternally inherited and broadened the genetic spectrum of Leigh syndrome, the most frequent paediatric mitochondrial disease. Herein, we characterize 28 so far unreported individuals from 26 families carrying a homozygous DNAJC30 p.Tyr51Cys founder variant, 24 manifesting with LHON, two manifesting with Leigh syndrome, and two remaining asymptomatic. This collection of unreported variant carriers confirms sex-dependent incomplete penetrance of the homozygous variant given a significant male predominance of disease and the report of asymptomatic homozygous variant carriers. The autosomal recessive LHON patients demonstrate an earlier age of disease onset and a higher rate of idebenone-treated and spontaneous recovery of vision in comparison to reported figures for maternally inherited disease. Moreover, the report of two additional patients with childhood- or adult-onset Leigh syndrome further evidences the association of DNAJC30 with Leigh syndrome, previously only reported in a single childhood-onset case. [ABSTRACT FROM AUTHOR]

Background: Lack of functional evidence hampers variant interpretation, leaving a large proportion of individuals with a suspected Mendelian disorder without genetic diagnosis after whole genome or whole exome sequencing (WES). Research studies advocate to further sequence transcriptomes to directly and systematically probe gene expression defects. However, collection of additional biopsies and establishment of lab workflows, analytical pipelines, and defined concepts in clinical interpretation of aberrant gene expression are still needed for adopting RNA sequencing (RNA-seq) in routine diagnostics. Methods: We implemented an automated RNA-seq protocol and a computational workflow with which we analyzed skin fibroblasts of 303 individuals with a suspected mitochondrial disease that previously underwent WES. We also assessed through simulations how aberrant expression and mono-allelic expression tests depend on RNA-seq coverage. Results: We detected on average 12,500 genes per sample including around 60% of all disease genes—a coverage substantially higher than with whole blood, supporting the use of skin biopsies. We prioritized genes demonstrating aberrant expression, aberrant splicing, or mono-allelic expression. The pipeline required less than 1 week from sample preparation to result reporting and provided a median of eight disease-associated genes per patient for inspection. A genetic diagnosis was established for 16% of the 205 WES-inconclusive cases. Detection of aberrant expression was a major contributor to diagnosis including instances of 50% reduction, which, together with mono-allelic expression, allowed for the diagnosis of dominant disorders caused by haploinsufficiency. Moreover, calling aberrant splicing and variants from RNA-seq data enabled detecting and validating splice-disrupting variants, of which the majority fell outside WES-covered regions. Conclusion: Together, these results show that streamlined experimental and computational processes can accelerate the implementation of RNA-seq in routine diagnostics. [ABSTRACT FROM AUTHOR]

Objective: ATP synthase (ATPase) is responsible for the majority of ATP production. Nevertheless, disease phenotypes associated with mutations in ATPase subunits are extremely rare. We aimed at expanding the spectrum of ATPase‐related diseases. Methods: Whole‐exome sequencing in cohorts with 2,962 patients diagnosed with mitochondrial disease and/or dystonia and international collaboration were used to identify deleterious variants in ATPase‐encoding genes. Findings were complemented by transcriptional and proteomic profiling of patient fibroblasts. ATPase integrity and activity were assayed using cells and tissues from 5 patients. Results: We present 10 total individuals with biallelic or de novo monoallelic variants in nuclear ATPase subunit genes. Three unrelated patients showed the same homozygous missense ATP5F1E mutation (including one published case). An intronic splice‐disrupting alteration in compound heterozygosity with a nonsense variant in ATP5PO was found in one patient. Three patients had de novo heterozygous missense variants in ATP5F1A, whereas another 3 were heterozygous for ATP5MC3 de novo missense changes. Bioinformatics methods and populational data supported the variants' pathogenicity. Immunohistochemistry, proteomics, and/or immunoblotting revealed significantly reduced ATPase amounts in association to ATP5F1E and ATP5PO mutations. Diminished activity and/or defective assembly of ATPase was demonstrated by enzymatic assays and/or immunoblotting in patient samples bearing ATP5F1A‐p.Arg207His, ATP5MC3‐p.Gly79Val, and ATP5MC3‐p.Asn106Lys. The associated clinical profiles were heterogeneous, ranging from hypotonia with spontaneous resolution (1/10) to epilepsy with early death (1/10) or variable persistent abnormalities, including movement disorders, developmental delay, intellectual disability, hyperlactatemia, and other neurologic and systemic features. Although potentially reflecting an ascertainment bias, dystonia was common (7/10). Interpretation: Our results establish evidence for a previously unrecognized role of ATPase nuclear‐gene defects in phenotypes characterized by neurodevelopmental and neurodegenerative features. ANN NEUROL 2022;91:225–237 [ABSTRACT FROM AUTHOR]

Subdural hematoma (SDH) was initially reported in 20% to 30% of patients with glutaric aciduria type 1 (GA1). A recent retrospective study found SDH in 4% of patients, but not in patients identified by newborn screening (NBS). 168 MRIs of 69 patients with GA1 (age at MRI 9 days – 73.8 years, median 3.2 years) were systematically reviewed for presence of SDH, additional MR and clinical findings in order to investigate the frequency of SDH and potential risk factors. SDH was observed in eight high‐excreting patients imaged between 5.8 and 24.4 months, namely space‐occupying SDH in two patients after minor accidental trauma and SDH as an incidental finding in six patients without trauma. In patients without trauma imaged at 3 to 30 months (n = 36, 25 NBS, 27/9 high/low excreters), incidence of SDH was 16.7% (16% in NBS). SDH was more common after acute (33.3%) than insidious onset of dystonia (14.3%) or in asymptomatic patients (5.9%). It was only seen in patients with wide frontoparietal CSF spaces and frontotemporal hypoplasia. High excreters were over‐represented among patients with SDH (6/27 vs 0/9 low excreters), acute onset (10/12), and wide frontoparietal CSF spaces (16/19). Incidental SDH occurs despite NBS and early treatment in approximately one in six patients with GA1 imaged during late infancy and early childhood. Greater risk of high excreters is morphologically associated with more frequent enlargement of external CSF spaces including frontotemporal hypoplasia, and may be furthered aggravated by more pronounced alterations of cerebral blood volume and venous pressure. [ABSTRACT FROM AUTHOR]

The aim of the study was a systematic evaluation of cognitive development in individuals with glutaric aciduria type 1 (GA1), a rare neurometabolic disorder, identified by newborn screening in Germany. This national, prospective, observational, multi-centre study includes 107 individuals with confirmed GA1 identified by newborn screening between 1999 and 2020 in Germany. Clinical status, development, and IQ were assessed using standardized tests. Impact of interventional and non-interventional parameters on cognitive outcome was evaluated. The majority of tested individuals (n = 72) showed stable IQ values with age (n = 56 with IQ test; median test age 11 years) but a significantly lower performance (median [IQR] IQ 87 [78–98]) than in general population, particularly in individuals with a biochemical high excreter phenotype (84 [75–96]) compared to the low excreter group (98 [92–105]; p = 0.0164). For all patients, IQ results were homogenous on subscale levels. Sex, clinical motor phenotype and quality of metabolic treatment had no impact on cognitive functions. Long-term neurologic outcome in GA1 involves both motor and cognitive functions. The biochemical high excreter phenotype is the major risk factor for cognitive impairment while cognitive functions do not appear to be impacted by current therapy and striatal damage. These findings implicate the necessity of new treatment concepts. [ABSTRACT FROM AUTHOR]

The aim of the study was a systematic evaluation of cognitive development in individuals with glutaric aciduria type 1 (GA1), a rare neurometabolic disorder, identified by newborn screening in Germany. This national, prospective, observational, multi-centre study includes 107 individuals with confirmed GA1 identified by newborn screening between 1999 and 2020 in Germany. Clinical status, development, and IQ were assessed using standardized tests. Impact of interventional and non-interventional parameters on cognitive outcome was evaluated. The majority of tested individuals (n = 72) showed stable IQ values with age (n = 56 with IQ test; median test age 11 years) but a significantly lower performance (median [IQR] IQ 87 [78–98]) than in general population, particularly in individuals with a biochemical high excreter phenotype (84 [75–96]) compared to the low excreter group (98 [92–105]; p = 0.0164). For all patients, IQ results were homogenous on subscale levels. Sex, clinical motor phenotype and quality of metabolic treatment had no impact on cognitive functions. Long-term neurologic outcome in GA1 involves both motor and cognitive functions. The biochemical high excreter phenotype is the major risk factor for cognitive impairment while cognitive functions do not appear to be impacted by current therapy and striatal damage. These findings implicate the necessity of new treatment concepts. [ABSTRACT FROM AUTHOR]

Background: During the initial 26-week SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) study, addition of sapropterin dihydrochloride (Kuvan®; a synthetic formulation of the natural cofactor for phenylalanine hydroxylase, tetrahydrobiopterin; BH4), to a phenylalanine (Phe)-restricted diet, led to a significant improvement in Phe tolerance versus a Phe-restricted diet alone in patients aged 0-4 years with BH4-responsive phenylketonuria (PKU) or mild hyperphenylalaninaemia (HPA). Based on these results, the approved indication for sapropterin in Europe was expanded to include patients < 4 years of age. Herein, we present results of the SPARK extension study (NCT01376908), evaluating the long-term safety, dietary Phe tolerance, blood Phe concentrations and neurodevelopmental outcomes in patients < 4 years of age at randomisation, over an additional 36 months of treatment with sapropterin.Results: All 51 patients who completed the 26-week SPARK study period entered the extension period. Patients who were previously treated with a Phe-restricted diet only ('sapropterin extension' group; n = 26), were initiated on sapropterin at 10 mg/kg/day, which could be increased up to 20 mg/kg/day. Patients previously treated with sapropterin plus Phe-restricted diet, remained on this regimen in the extension period ('sapropterin continuous' group; n = 25). Dietary Phe tolerance increased significantly at the end of the study versus baseline (week 0), by 38.7 mg/kg/day in the 'sapropterin continuous' group (95% CI 28.9, 48.6; p < 0.0001). In the 'sapropterin extension' group, a less pronounced effect was observed, with significant differences versus baseline (week 27) only observed between months 9 and 21; dietary Phe tolerance at the end of study increased by 5.5 mg/kg/day versus baseline (95% CI - 2.8, 13.8; p = 0.1929). Patients in both groups had normal neuromotor development and growth parameters.Conclusions: Long-term treatment with sapropterin plus a Phe-restricted diet in patients who initiated sapropterin at < 4 years of age with BH4-responsive PKU or mild HPA maintained improvements in dietary Phe tolerance over 3.5 years. These results continue to support the favourable risk/benefit profile for sapropterin in paediatric patients (< 4 years of age) with BH4-responsive PKU. Frequent monitoring of blood Phe levels and careful titration of dietary Phe intake to ensure adequate levels of protein intake is necessary to optimise the benefits of sapropterin treatment. Trial registration ClinicalTrials.gov, NCT01376908. Registered 17 June 2011, https://clinicaltrials.gov/ct2/show/NCT01376908 . [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Glutaric aciduria type 1 (GA1) is a rare neurometabolic disorder, caused by inherited deficiency of glutaryl‐CoA dehydrogenase, mostly affecting the brain. Early identification by newborn screening (NBS) significantly improves neurologic outcome. It has remained unclear whether recommended therapy, particular low lysine diet, is safe or negatively affects anthropometric long‐term outcome. This national prospective, observational, multi‐centre study included 79 patients identified by NBS and investigated effects of interventional and non‐interventional parameters on body weight, body length, body mass index (BMI) and head circumference as well as neurological parameters. Adherence to recommended maintenance and emergency treatment (ET) had a positive impact on neurologic outcome and allowed normal anthropometric development until adulthood. In contrast, non‐adherence to ET, resulting in increased risk of dystonia, had a negative impact on body weight (mean SDS −1.07; P =.023) and body length (mean SDS −1.34; P = −.016). Consistently, longitudinal analysis showed a negative influence of severe dystonia on weight and length development over time (P <.001). Macrocephaly was more often found in female (mean SDS 0.56) than in male patients (mean SDS −0.20; P =.049), and also in individuals with high excreter phenotype (mean SDS 0.44) compared to low excreter patients (mean SDS −0.68; P =.016). In GA1, recommended long‐term treatment is effective and allows for normal anthropometric long‐term development up to adolescence, with gender‐ and excreter type‐specific variations. Delayed ET and severe movement disorder result in poor anthropometric outcome. [ABSTRACT FROM AUTHOR]

Background: Acute hyperammonemia without signs of common causes in the elderly might be challenging to identify. We report the oldest case known to date of a female patient with late onset ornithine carbamyltransferase deficiency (OTC), which was unmasked after a protein overload due to nutritional supplements. Our case illustrates how environmental factors (protein overload) in previously unknown OTC in the elderly leads to hyperammonemic encephalopathy and highlights that early treatment prevents persisting neurological deficits and should be considered in absence of common causes of hyperammonemic encephalopathy.Case Presentation: A 68-year-old woman presented with acute confusion, which progressed into a deep coma (Glasgow-Coma-Scale score 3) within a few hours. The only remarkable finding was a plasma ammonia (NH3) concentration of 697 μmmol/l (range 12-47 μmmol/). Third party history revealed that the patient disliked meat for most of her life (meat = protein, which needs to be metabolized) and had taken nutritional supplements (since supplements often have a high protein-ratio) 2 days before the symptoms started. Protein catabolism results in NH3, which is metabolized via the urea cycle. Consequently, the acute hyperammonemia in our patient was thought to be related to an inherited metabolic disorder, which only unmasked itself as a result of an overload of the corresponding metabolite (in this case protein). Since ornithine carbamyltransferase deficiency (OTC) is the most common inherited urea cycle disorder, this diagnosis became likely and was confirmed later via genetic and metabolic testing (amino acids, orotic acid, etc.). After 2 weeks of treatment (dialysis, low-protein-diet, nitrogen-lowering medication) the patient was discharged in a healthy condition without any neurological deficits.Conclusion: OTC is a x-chromosomal linked disorder, that usually manifests in newborn infants and children, but also rarely in adults and even rarer in the elderly (50- till 60-years-old), where it is probably underdiagnosed. In case of hyperammonemic encephalopathy - regardless of the underlying cause -, treatment should be started early to prevent persisting neurological deficits. OTC should be considered in absence of common causes of hyperammonemic encephalopathy. [ABSTRACT FROM AUTHOR]

Background: Phenylketonuria (PKU; OMIM#261600) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene resulting in high phenylalanine (Phe) in blood and brain. If not treated early this results in intellectual disability, behavioral and psychiatric problems, microcephaly, motor deficits, eczematous rash, autism, seizures, and developmental problems. There is a controversial discussion of whether patients with PKU have an additional risk for atherosclerosis due to interference of Phe with cholesterol synthesis and LDL-cholesterol regulation. Since cholesterol also plays a role in membrane structure and myelination, better insight into the clinical significance of the impact of Phe on lipoprotein metabolism is desirable. In 22 treated PKU patients (mean age 38.7 years) and 14 healthy controls (mean age 35.2 years), we investigated plasma with NMR spectroscopy and quantified 105 lipoprotein parameters (including lipoprotein subclasses) and 24 low molecular weight parameters. Analysis was performed on a 600 MHz Bruker AVANCE IVDr spectrometer as previously described.Results: Concurrent plasma Phe in PKU patients showed a wide range with a mean of 899 μmol/L (50-1318 μmol/L). Total cholesterol and LDL-cholesterol were significantly lower in PKU patients versus controls: 179.4 versus 200.9 mg/dL (p < 0.02) and 79.5 versus 104.1 mg/dL (p < 0.0038), respectively. PKU patients also had lower levels of 22 LDL subclasses with the greatest differences in LDL2 Apo-B, LDL2 Particle Number, LDL2-phospholipids, and LDL2-cholesterol (p < 0.0001). There was a slight negative correlation of total cholesterol and LDL-cholesterol with concurrent Phe level. VLDL5-free cholesterol, VLDL5-cholesterol, VLDL5-phospholipids, and VLDL4-free cholesterol showed a significant (p < 0.05) negative correlation with concurrent Phe level. There was no difference in HDL and their subclasses between PKU patients and controls. Tyrosine, glutamine, and creatinine were significantly lower in PKU patients compared to controls, while citric and glutamic acids were significantly higher.Conclusions: Using NMR spectroscopy, a unique lipoprotein profile in PKU patients can be demonstrated which mimics a non-atherogenic profile as seen in patients treated by statins. [ABSTRACT FROM AUTHOR]

Pyruvate carboxylase deficiency (PCD) is caused by biallelic mutations of the PC gene. The reported clinical spectrum includes a neonatal form with early death (type B), an infantile fatal form (type A), and a late‐onset form with isolated mild intellectual delay (type C). Apart from homozygous stop‐codon mutations leading to type B PCD, a genotype–phenotype correlation has not otherwise been discernible. Indeed, patients harboring biallelic heterozygous variants leading to PC activity near zero can present either with a fatal infantile type A or with a benign late onset type C form. In this study, we analyzed six novel patients with type A (three) and type C (three) PCD, and compared them with previously reported cases. First, we observed that type C PCD is not associated to homozygous variants in PC. In silico modeling was used to map former and novel variants associated to type A and C PCD, and to predict their potential effects on the enzyme structure and function. We found that variants lead to type A or type C phenotype based on the destabilization between the two major enzyme conformers. In general, our study on novel and previously reported patients improves the overall understanding on type A and C PCD. [ABSTRACT FROM AUTHOR]

Biogenic amines synthesis in phenylketonuria (PKU) patients with high phenylalanine (Phe) concentration is thought to be impaired due to inhibition of tyrosine and tryptophan hydroxylases and competition with amino acids at the blood‐brain barrier. Dopamine and serotonin deficits might explain brain damage and progressive neuropsychiatric impairment in adult PKU patients. Ten early treated adult PKU patients (mean age 38.2 years) and 15 age‐matched controls entered the study. Plasma and cerebrospinal fluid (CSF) Phe, 5‐hydroxyindoleacetic acid (5‐HIAA), 5‐hydroxytryptophan (5‐HTP), 3,4‐dihydroxy‐l‐phenylalanine (l‐DOPA) and homovanillic acid (HVA) were analyzed. Voxel‐based morphometry statistical nonparametric mapping was used to test the age‐corrected correlation between gray matter atrophy and CSF biogenic amines levels. 5‐HIAA and 5‐HTP were significantly reduced in PKU patients compared to controls. Significant negative correlations were found between CSF 5‐HIAA, HVA, and 5‐HTP and Phe levels. A decrease in 5‐HIAA and 5‐HTP concentrations correlated with precuneus and frontal atrophy, respectively. Lower HVA levels correlated with occipital atrophy. Biogenic amines deficits correlate with specific brain atrophy patterns in adult PKU patients, in line with serotonin and dopamine projections. These findings may support a more rigorous Phe control in adult PKU to prevent neurotransmitter depletion and accelerated brain damage due to aging. [ABSTRACT FROM AUTHOR]

Background Primary microcephaly and profound global developmental delay have been considered the core clinical phenotype in patients with bi-allelic PRUNE1 mutations. Methods Linkage analysis and whole-exome sequencing (WES) in a multiplex family and extraction of further cases from a WES repository containing 571 children with severe developmental disabilities and neurologic symptoms. Results We identified bi-allelic PRUNE1 mutations in twelve children from six unrelated families. All patients who survived beyond the first 6 months of life had early-onset global developmental delay, bilateral spastic paresis, dysphagia and difficult-to-treat seizures, while congenital or later-evolving microcephaly was not a consistent finding. Brain MRI showed variable anomalies with progressive cerebral and cerebellar atrophies and T2- hyperintense brain stem lesions. Peripheral neuropathy was documented in five cases. Disease course was progressive in all patients and eight children died in the first or early second decade of life. In addition to the previously reportedmissensemutation p. (Asp106Asn), we observed a novel homozygous missense variant p.(Leu172Pro) and a homozygous contiguous gene deletion encompassing most of the PRUNE1 gene and part of the neighboring BNIPL gene. Conclusions PRUNE1 deficiency causes severe early-onset disease affecting the central and peripheral nervous systems. Microcephaly is probably not a universal feature. [ABSTRACT FROM AUTHOR]

Objective: Untreated individuals with glutaric aciduria type 1 (GA1) commonly present with a complex, predominantly dystonic movement disorder (MD) following acute or insidious onset striatal damage. Implementation of GA1 into newborn screening (NBS) programs has improved the short-term outcome. It remains unclear, however, whether NBS changes the long-term outcome and which variables are predictive.Methods: This prospective, observational, multicenter study includes 87 patients identified by NBS, 4 patients missed by NBS, and 3 women with GA1 identified by positive NBS results of their unaffected children.Results: The study population comprises 98.3% of individuals with GA1 identified by NBS in Germany during 1999-2016. Overall, cumulative sensitivity of NBS is 95.6%, but it is lower (84%) for patients with low excreter phenotype. The neurologic outcome of patients missed by NBS is as poor as in the pre-NBS era, and the clinical phenotype of diagnosed patients depends on the quality of therapeutic interventions rather than noninterventional variables. Presymptomatic start of treatment according to current guideline recommendations clearly improves the neurologic outcome (MD: 7% of patients), whereas delayed emergency treatment results in acute onset MD (100%), and deviations from maintenance treatment increase the risk of insidious onset MD (50%). Independent of the neurologic phenotype, kidney function tends to decline with age, a nonneurologic manifestation not predicted by any variable included in this study.Interpretation: NBS is a beneficial, disease-changing intervention for GA1. However, improved neurologic outcome critically depends on adherence to recommended therapy, whereas kidney dysfunction does not appear to be impacted by recommended therapy. Ann Neurol 2018;83:970-979. [ABSTRACT FROM AUTHOR]

Objective: 3-Methylglutaconic aciduria, dystonia-deafness, hepatopathy, encephalopathy, Leigh-like syndrome (MEGDHEL) syndrome is caused by biallelic variants in SERAC1.Methods: This multicenter study addressed the course of disease for each organ system. Metabolic, neuroradiological, and genetic findings are reported.Results: Sixty-seven individuals (39 previously unreported) from 59 families were included (age range = 5 days-33.4 years, median age = 9 years). A total of 41 different SERAC1 variants were identified, including 20 that have not been reported before. With the exception of 2 families with a milder phenotype, all affected individuals showed a strikingly homogeneous phenotype and time course. Severe, reversible neonatal liver dysfunction and hypoglycemia were seen in >40% of all cases. Starting at a median age of 6 months, muscular hypotonia (91%) was seen, followed by progressive spasticity (82%, median onset = 15 months) and dystonia (82%, 18 months). The majority of affected individuals never learned to walk (68%). Seventy-nine percent suffered hearing loss, 58% never learned to speak, and nearly all had significant intellectual disability (88%). Magnetic resonance imaging features were accordingly homogenous, with bilateral basal ganglia involvement (98%); the characteristic "putaminal eye" was seen in 53%. The urinary marker 3-methylglutaconic aciduria was present in virtually all patients (98%). Supportive treatment focused on spasticity and drooling, and was effective in the individuals treated; hearing aids or cochlear implants did not improve communication skills.Interpretation: MEGDHEL syndrome is a progressive deafness-dystonia syndrome with frequent and reversible neonatal liver involvement and a strikingly homogenous course of disease. Ann Neurol 2017;82:1004-1015. [ABSTRACT FROM AUTHOR]

Mitochondrial protein synthesis involves an intricate interplay between mitochondrial DNA encoded RNAs and nuclear DNA encoded proteins, such as ribosomal proteins and aminoacyl-tRNA synthases. Eukaryotic cells contain 17 mitochondria-specific aminoacyl-tRNA synthases. WARS2 encodes mitochondrial tryptophanyl-tRNA synthase (mtTrpRS), a homodimeric class Ic enzyme (mitochondrial tryptophan-tRNA ligase; EC 6.1.1.2). Here, we report six individuals from five families presenting with either severe neonatal onset lactic acidosis, encephalomyopathy and early death or a later onset, more attenuated course of disease with predominating intellectual disability. Respiratory chain enzymes were usually normal in muscle and fibroblasts, while a severe combined respiratory chain deficiency was found in the liver of a severely affected individual. Exome sequencing revealed rare biallelic variants in WARS2 in all affected individuals. An increase of uncharged mitochondrial tRNATrp and a decrease of mtTrpRS protein content were found in fibroblasts of affected individuals. We hereby define the clinical, neuroradiological, and metabolic phenotype of WARS2 defects. This confidently implicates that mutations in WARS2 cause mitochondrial disease with a broad spectrum of clinical presentation. [ABSTRACT FROM AUTHOR]

Background: Sapropterin dihydrochloride, a synthetic formulation of BH4, the cofactor for phenylalanine hydroxylase (PAH, EC 1.14.16.1), was initially approved in Europe only for patients ≥4 years with BH4-responsive phenylketonuria. The aim of the SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) trial was to assess the efficacy (improvement in daily phenylalanine tolerance, neuromotor development and growth parameters), safety and pharmacokinetics of sapropterin dihydrochloride in children <4 years.Results: In total, 109 male or female children <4 years with confirmed BH4-responsive phenylketonuria or mild hyperphenylalaninemia and good adherence to dietary treatment were screened. 56 patients were randomly assigned (1:1) to 10 mg/kg/day oral sapropterin plus a phenylalanine-restricted diet or to only a phenylalanine-restricted diet for 26 weeks (27 to the sapropterin and diet group and 29 to the diet-only group; intention-to-treat population). Of these, 52 patients with ≥1 pharmacokinetic sample were included in the pharmacokinetic analysis, and 54 patients were included in the safety analysis. At week 26 in the sapropterin plus diet group, mean phenylalanine tolerance was 30.5 (95% confidence interval 18.7-42.3) mg/kg/day higher than in the diet-only group (p < 0.001). The safety profile of sapropterin, measured monthly, was acceptable and consistent with that seen in studies of older children. Using non-linear mixed effect modelling, a one-compartment model with flip-flop pharmacokinetic behaviour, in which the effect of weight was substantial, best described the pharmacokinetic profile. Patients in both groups had normal neuromotor development and stable growth parameters.Conclusions: The addition of sapropterin to a phenylalanine-restricted diet was well tolerated and led to a significant improvement in phenylalanine tolerance in children <4 years with BH4-responsive phenylketonuria or mild hyperphenylalaninemia. The pharmacokinetic model favours once per day dosing with adjustment for weight. Based on the SPARK trial results, sapropterin has received EU approval to treat patients <4 years with BH4-responsive phenylketonuria.Trial Registration: ClinicalTrials.gov, NCT01376908 . Registered June 17, 2011. [ABSTRACT FROM AUTHOR]

Background and aim: To describe current diagnostic and therapeutic strategies in organic acidurias (OADs) and to evaluate their impact on the disease course allowing harmonisation. Methods: Datasets of 567 OAD patients from the E-IMD registry were analysed. The sample includes patients with methylmalonic (MMA, n = 164), propionic (PA, n = 144) and isovaleric aciduria (IVA, n = 83), and glutaric aciduria type 1 (GA1, n = 176). Statistical analysis included description and recursive partitioning of diagnostic and therapeutic strategies, and odds ratios (OR) for health outcome parameters. For some analyses, symptomatic patients were divided into those presenting with first symptoms during (i.e. early onset, EO) or after the newborn period (i.e. late onset, LO). Results: Patients identified by newborn screening (NBS) had a significantly lower median age of diagnosis (8 days) compared to the LO group (363 days, p < 0.001], but not compared to the EO group. Of all OAD patients 71 % remained asymptomatic until day 8. Patients with cobalamin-nonresponsive MMA (MMA-Cbl) and GA1 identified by NBS were less likely to have movement disorders than those diagnosed by selective screening (MMA-Cbl: 10 % versus 39 %, p = 0.002; GA1: 26 % versus 73 %, p < 0.001). For other OADs, the clinical benefit of NBS was less clear. Reported age-adjusted intake of natural protein and calories was significantly higher in LO patients than in EO patients reflecting different disease severities. Variable drug combinations, ranging from 12 in MMA-Cbl to two in isovaleric aciduria, were used for maintenance treatment. The effects of specific metabolic treatment strategies on the health outcomes remain unclear because of the strong influences of age at onset (EO versus LO), diagnostic mode (NBS versus selective screening), and the various treatment combinations used. Conclusions: NBS is an effective intervention to reduce time until diagnosis especially for LO patients and to prevent irreversible cerebral damage in GA1 and MMA-Cbl. Huge diversity of therapeutic interventions hampers our understanding of optimal treatment. [ABSTRACT FROM AUTHOR]

Background Mitochondria are dynamic organelles which undergo continuous fission and fusion to maintain their diverse cellular functions. Components of the fission machinery are partly shared between mitochondria and peroxisomes, and inherited defects in two such components (dynamin-related protein (DRP1) and ganglioside-induced differentiation-associated protein 1 (GDAP1)) have been associated with human disease. Deficiency of a third component (mitochondrial fission factor, MFF) was recently reported in one index patient, rendering MFF another candidate disease gene within the expanding field of mitochondrial and peroxisomal dynamics. Here we investigated three new patients from two families with pathogenic mutations in MFF. Methods The patients underwent clinical examination, brain MRI, and biochemical, cytological and molecular analyses, including exome sequencing. Results The patients became symptomatic within the first year of life, exhibiting seizures, developmental delay and acquired microcephaly. Dysphagia, spasticity and optic and peripheral neuropathy developed subsequently. Brain MRI showed Leigh-like patterns with bilateral changes of the basal ganglia and subthalamic nucleus, suggestive of impaired mitochondrial energy metabolism. However, activities of mitochondrial respiratory chain complexes were found to be normal in skeletal muscle. Exome sequencing revealed three different biallelic loss-of-function variants in MFF in both index cases. Western blot studies of patientderived fibroblasts indicated normal content of mitochondria and peroxisomes, whereas immunofluorescence staining revealed elongated mitochondria and peroxisomes. Furthermore, increased mitochondrial branching and an abnormal distribution of fission-mediating DRP1 were observed. Conclusions Our findings establish MFF loss of function as a cause of disturbed mitochondrial and peroxisomal dynamics associated with early-onset Leigh-like basal ganglia disease. We suggest that, even if laboratory findings are not indicative of mitochondrial or peroxisomal dysfunction, the co-occurrence of optic and/or peripheral neuropathy with seizures warrants genetic testing for MFF mutations. [ABSTRACT FROM AUTHOR]

Background: Adenosine kinase deficiency is a recently described defect affecting methionine metabolism with a severe clinical phenotype comprising mainly neurological and hepatic impairment and dysmorphism. Methods: Clinical data of 11 additional patients from eight families with adenosine kinase deficiency were gathered through a retrospective questionnaire. Two liver biopsies of one patient were systematically evaluated. Results: The main clinical symptoms are mild to severe liver dysfunction with neonatal onset, muscular hypotonia, global developmental retardation and dysmorphism (especially frontal bossing). Hepatic involvement is not a constant finding. Most patients have epilepsy and recurrent hypoglycemia due to hyperinsulinism. Major biochemical findings are intermittent hypermethioninemia, increased S-adenosylmethionine and S-adenosylhomocysteine in plasma and increased adenosine in urine. S-adenosylmethionine and S-adenosylhomocysteine are the most reliable biochemical markers. The major histological finding was pronounced microvesicular hepatic steatosis. Therapeutic trials with a methionine restricted diet indicate a potential beneficial effect on biochemical and clinical parameters in four patients and hyperinsulinism was responsive to diazoxide in two patients. Conclusion: Adenosine kinase deficiency is a severe inborn error at the cross-road of methionine and adenosine metabolism that mainly causes dysmorphism, brain and liver symptoms, but also recurrent hypoglycemia. The clinical phenotype varies from an exclusively neurological to a multi-organ manifestation. Methionine-restricted diet should be considered as a therapeutic option. [ABSTRACT FROM AUTHOR]

Background: Acute liver failure (ALF) in infancy and childhood is a life-threatening emergency and in about 50 % the etiology remains unknown. Recently biallelic mutations in NBAS were identified as a new molecular cause of ALF with onset in infancy, leading to recurrent acute liver failure (RALF). Methods: The phenotype and medical history of 14 individuals with NBAS deficiency was studied in detail and functional studies were performed on patients' fibroblasts. Results: The phenotypic spectrum of NBAS deficiency ranges from isolated RALF to a multisystemic disease with short stature, skeletal dysplasia, immunological abnormalities, optic atrophy, and normal motor and cognitive development resembling SOPH syndrome. Liver crises are triggered by febrile infections; they become less frequent with age but are not restricted to childhood. Complete recovery is typical, but ALF crises can be fatal. Antipyretic therapy and induction of anabolism including glucose and parenteral lipids effectively ameliorates the course of liver crises. Patients' fibroblasts showed an increased sensitivity to high temperature at protein and functional level and a disturbed tethering of vesicles, pointing at a defect of intracellular transport between the endoplasmic reticulum and Golgi. Conclusions: Mutations in NBAS cause a complex disease with a wide clinical spectrum ranging from isolated RALF to a multisystemic phenotype. Thermal susceptibility of the syntaxin 18 complex is the basis of fever dependency of ALF episodes. NBAS deficiency is the first disease related to a primary defect of retrograde transport. Identification of NBAS deficiency allows optimized therapy of liver crises and even prevention of further episodes. [ABSTRACT FROM AUTHOR]

FBXL4 deficiency is a recently described disorder of mitochondrial maintenance associated with a loss of mitochondrial DNA in cells. To date, the genetic diagnosis of FBXL4 deficiency has been established in 28 individuals. This paper retrospectively reviews proxy-reported clinical and biochemical findings and evaluates brain imaging, morphological and genetic data in 21 of those patients. Neonatal/early-onset severe lactic acidosis, muscular hypotonia, feeding problems and failure to thrive is the characteristic pattern at first presentation. Facial dysmorphic features are present in 67 % of cases. Seven children died (mean age 37 months); 11 children were alive (mean age at follow-up 46 months), three children were lost to follow-up. All survivors developed severe psychomotor retardation. Brain imaging was non-specific in neonates but a later-onset, rapidly progressive brain atrophy was noted. Elevated blood lactate and metabolic acidosis were observed in all individuals; creatine kinase was elevated in 45 % of measurements. Diagnostic workup in patient tissues and cells revealed a severe combined respiratory chain defect with a general decrease of enzymes associated with mitochondrial energy metabolism and a relative depletion of mitochondrial DNA content. Mutations were detected throughout the FBXL4 gene albeit with no clear delineation of a genotype-phenotype correlation. Treatment with 'mitochondrial medications' did not prove effective. In conclusion, a clinical pattern of early-onset encephalopathy, persistent lactic acidosis, profound muscular hypotonia and typical facial dysmorphism should prompt initiation of molecular genetic analysis of FBXL4. Establishment of the diagnosis permits genetic counselling, prevents patients undergoing unhelpful diagnostic procedures and allows for accurate prognosis. [ABSTRACT FROM AUTHOR]

Inherited disorders of mitochondrial energy metabolism form a large and heterogeneous group of metabolic diseases. More than 250 gene defects have been reported to date and this number continues to grow. Mitochondrial diseases can be grouped into (1) disorders of oxidative phosphorylation (OXPHOS) subunits and their assembly factors, (2) defects of mitochondrial DNA, RNA and protein synthesis, (3) defects in the substrate-generating upstream reactions of OXPHOS, (4) defects in relevant cofactors and (5) defects in mitochondrial homeostasis. Deficiency of more than one respiratory chain enzyme is a common finding. Combined defects are found in 49 % of the known disease-causing genes of mitochondrial energy metabolism and in 57 % of patients with OXPHOS defects identified in our diagnostic centre. Combined defects of complexes I, III, IV and V are typically due to deficiency of mitochondrial DNA replication, RNA metabolism or translation. Defects in cofactors can result in combined defects of various combinations, and defects of mitochondrial homeostasis can result in a generalised decrease of all OXPHOS enzymes. Noteworthy, identification of combined defects can be complicated by different degrees of severity of each affected enzyme. Furthermore, even defects of single respiratory chain enzymes can result in combined defects due to aberrant formation of respiratory chain supercomplexes. Combined OXPHOS defects have a great variety of clinical manifestations in terms of onset, course severity and tissue involvement. They can present as classical encephalomyopathy but also with hepatopathy, nephropathy, haematologic findings and Perrault syndrome in a subset of disorders. [ABSTRACT FROM AUTHOR]

Objective Short-chain enoyl-CoA hydratase ( ECHS1) is a multifunctional mitochondrial matrix enzyme that is involved in the oxidation of fatty acids and essential amino acids such as valine. Here, we describe the broad phenotypic spectrum and pathobiochemistry of individuals with autosomal-recessive ECHS1 deficiency. Methods Using exome sequencing, we identified ten unrelated individuals carrying compound heterozygous or homozygous mutations in ECHS1. Functional investigations in patient-derived fibroblast cell lines included immunoblotting, enzyme activity measurement, and a palmitate loading assay. Results Patients showed a heterogeneous phenotype with disease onset in the first year of life and course ranging from neonatal death to survival into adulthood. The most prominent clinical features were encephalopathy (10/10), deafness (9/9), epilepsy (6/9), optic atrophy (6/10), and cardiomyopathy (4/10). Serum lactate was elevated and brain magnetic resonance imaging showed white matter changes or a Leigh-like pattern resembling disorders of mitochondrial energy metabolism. Analysis of patients' fibroblast cell lines (6/10) provided further evidence for the pathogenicity of the respective mutations by showing reduced ECHS1 protein levels and reduced 2-enoyl-CoA hydratase activity. While serum acylcarnitine profiles were largely normal, in vitro palmitate loading of patient fibroblasts revealed increased butyrylcarnitine, unmasking the functional defect in mitochondrial β-oxidation of short-chain fatty acids. Urinary excretion of 2-methyl-2,3-dihydroxybutyrate - a potential derivative of acryloyl-CoA in the valine catabolic pathway - was significantly increased, indicating impaired valine oxidation. Interpretation In conclusion, we define the phenotypic spectrum of a new syndrome caused by ECHS1 deficiency. We speculate that both the β-oxidation defect and the block in l-valine metabolism, with accumulation of toxic methacrylyl-CoA and acryloyl-CoA, contribute to the disorder that may be amenable to metabolic treatment approaches. [ABSTRACT FROM AUTHOR]

Pyruvate oxidation defects (PODs) are among the most frequent causes of deficiencies in the mitochondrial energy metabolism and represent a substantial subset of classical mitochondrial diseases. PODs are not only caused by deficiency of subunits of the pyruvate dehydrogenase complex (PDHC) but also by various disorders recently described in the whole pyruvate oxidation route including cofactors, regulation of PDHC and the mitochondrial pyruvate carrier. Our own patients from 2000 to July 2014 and patients identified by a systematic survey of the literature from 1970 to July 2014 with a pyruvate oxidation disorder and a genetically proven defect were included in the study (n=628). Of these defects 74.2% (n=466) belong to PDHC subunits, 24.5% (n=154) to cofactors, 0.5% (n=3) to PDHC regulation and 0.8% (n=5) to mitochondrial pyruvate import. PODs are underestimated in the field of mitochondrial diseases because not all diagnostic centres include biochemical investigations of PDHC in their routine analysis. Cofactor and transport defects can be missed, if pyruvate oxidation is not measured in intact mitochondria routinely. Furthermore deficiency of the X-chromosomal PDHA1 can be biochemically missed depending on the X-inactivation pattern. This is reflected by an increasing number of patients diagnosed recently by genetic high throughput screening approaches. PDHC deficiency including regulation and import affect mainly the glucose dependent central and peripheral nervous system and skeletal muscle. PODs with combined enzyme defects affect also other organs like heart, lung and liver. The spectrum of clinical presentation of PODs is still expanding. PODs are a therapeutically interesting group of mitochondrial diseases since some can be bypassed by ketogenic diet or treated by cofactor supplementation. PDHC kinase inhibition, chaperone therapy and PGC1α stimulation is still a matter of further investigations. [ABSTRACT FROM AUTHOR]

The mitochondrial pyruvate oxidation route is a tightly regulated process, which is essential for aerobic cellular energy production. Disruption of this pathway may lead to severe neurometabolic disorders with onset in early childhood. A frequent finding in these patients is acute and chronic lactic acidemia, which is caused by increased conversion of pyruvate via the enzyme lactate dehydrogenase. Under stable clinical conditions, this process may remain well compensated and does not require specific therapy. However, especially in situations with altered energy demands, such as febrile infections or longer periods of fasting, children with mitochondrial disorders have a high risk of metabolic decompensation with exacerbation of hyperlactatemia and severe metabolic acidosis. Unfortunately, no controlled studies regarding therapy of this critical condition are available and clinical outcome is often unfavorable. Therefore, the aim of this review was to formulate expert-based suggestions for treatment of these patients, including dietary recommendations, buffering strategies and specific drug therapy. However, it is important to keep in mind that a specific therapy for the underlying metabolic cause in children with mitochondrial diseases is usually not available and symptomatic therapy especially of severe lactic acidosis has its ethical limitations. [ABSTRACT FROM AUTHOR]

Background: TTC19 deficiency is a progressive neurodegenerative disease associated with isolated mitochondrial respiratory chain (MRC) complex III deficiency and loss-of-function mutations in the TT19 gene in the few patients reported so far. Methods: We performed exome sequencing and selective mutational analysis of TTC19, respectively, in patients from three unrelated families presenting with initially unspecific clinical signs of muscular hypotonia and global developmental delay followed by regression, ataxia, loss of speech, and rapid neurological deterioration. One patient showed severe lactic acidosis at the neonatal age and during intercurrent illness. Results: We identified homozygous mutations in all three index cases, in two families novel missense mutations (c.544 T > C/p.Leu185Pro; c.917 T > C/p.Leu324Pro). The younger sister of the severely affected patient 3 showed only mild delay of motor skills and muscular hypotonia so far but is also homozygous for the same mutation. Notably, one patient revealed normal activities of MRC complex III in two independent muscle biopsies. Neuroimaging of the severely affected patients demonstrated lesions in putamen and caudate nuclei, cerebellar atrophy, and the unusual finding of hypertrophic olivary nuclei degeneration. Reviewing the literature revealed striking similarities regarding neuroimaging and clinical course in pediatric patients with TTC19 deficiency: patterns consistent with Leigh or Leigh-like syndrome were found in almost all, hypertrophic olivary nucleus degeneration in all patients reported so far. The clinical course in pediatric patients is characterized by an initially unspecific developmental delay, followed by regression, progressive signs and symptoms of cerebellar, basal ganglia and brainstem affection, especially loss of speech and ataxia. Subsequently, neurological deterioration leading to a vegetative state occurs. Conclusions: Our findings add to the phenotypic, genetic, and biochemical spectrum of TTC19 deficiency. However, TTC19 deficient patients do show characteristic clinical and neuroimaging features, which may facilitate diagnosis of this yet rare disorder. Normal MRC complex III activity does not exclude the diagnosis. [ABSTRACT FROM AUTHOR]

Defects of mitochondrial oxidative phosphorylation constitute a clinical and genetic heterogeneous group of disorders affecting multiple organ systems at varying age. Biochemical analysis of biopsy material demonstrates isolated or combined deficiency of mitochondrial respiratory chain enzyme complexes. Co-occurrence of impaired activity of the pyruvate dehydrogenase complex has been rarely reported so far and is not yet fully understood. We investigated two siblings presenting with severe neonatal lactic acidosis, hypotonia, and intractable cardiomyopathy; both died within the first months of life. Muscle biopsy revealed a peculiar biochemical defect consisting of a combined deficiency of respiratory chain complexes I, II, and II+III accompanied by a defect of the pyruvate dehydrogenase complex. Joint exome analysis of both affected siblings uncovered a homozygous missense mutation in BOLA3. The causal role of the mutation was validated by lentiviral-mediated expression of the mitochondrial isoform of wildtype BOLA3 in patient fibroblasts, which lead to an increase of both residual enzyme activities and lipoic acid levels. Our results suggest that BOLA3 plays a crucial role in the biogenesis of iron-sulfur clusters necessary for proper function of respiratory chain and 2-oxoacid dehydrogenase complexes. We conclude that broad sequencing approaches combined with appropriate prioritization filters and experimental validation enable efficient molecular diagnosis and have the potential to discover new disease loci. [ABSTRACT FROM AUTHOR]

Brown-Vialetto-Van Laere syndrome (BVVLS [MIM 211530]) is a rare neurological disorder characterized by infancy onset sensorineural deafness and ponto-bulbar palsy. Mutations in SLC52A3 (formerly C20orf54), coding for riboflavin transporter 2 (hRFT2), have been identified as the molecular genetic correlate in several individuals with BVVLS. Exome sequencing of just one single case revealed that compound heterozygosity for two pathogenic mutations in the SLC52A2 gene coding for riboflavin transporter 3 (hRFT3), another member of the riboflavin transporter family, is also associated with BVVLS. Overexpression studies confirmed that the gene products of both mutant alleles have reduced riboflavin transport activities. While mutations in SLC52A3 cause decreased plasma riboflavin levels, concordant with a role of SLC52A3 in riboflavin uptake from food, the SLC52A2-mutant individual had normal plasma riboflavin concentrations, a finding in line with a postulated function of SLC52A2 in riboflavin uptake from blood into target cells. Our results contribute to the understanding of human riboflavin metabolism and underscore its role in the pathogenesis of BVVLS, thereby providing a rational basis for a high-dose riboflavin treatment. [ABSTRACT FROM AUTHOR]

Objective Mitochondrial disturbances of energygenerating systems in childhood are a heterogeneous group of disorders. The aim of this multi-site survey was to characterise the natural course of a novel mitochondrial disease with ATP synthase deficiency and mutation in the TMEM70 gene. Methods Retrospective clinical data and metabolic profiles were collected and evaluated in 25 patients (14 boys, 11 girls) from seven European countries with a c.317-2A→G mutation in the TMEM70 gene. Results Severe muscular hypotonia (in 92% of newborns), apnoic spells (92%), hypertrophic cardiomyopathy (HCMP; 76%) and profound lactic acidosis (lactate 5-36 mmol/l; 92%) with hyperammonaemia (100-520 μmol/l; 86%) were present from birth. Ten patients died within the first 6 weeks of life. Most patients surviving the neonatal period had persisting muscular hypotonia and developed psychomotor delay. HCMP was non-progressive and even disappeared in some children. Hypospadia was present in 54% of the boys and cryptorchidism in 67%. Increased excretion of lactate and 3-methylglutaconic acid (3-MGC) was observed in all patients. In four surviving patients, life-threatening hyperammonaemia occurred during childhood, triggered by acute gastroenteritis and prolonged fasting. Conclusions ATP synthase deficiency with mutation in TMEM70 should be considered in the diagnosis and management of critically ill neonates with early neonatal onset of muscular hypotonia, HCMP and hypospadias in boys accompanied by lactic acidosis, hyperammonaemia and 3-MGC-uria. However, phenotype severity may vary significantly. The disease occurs frequently in the Roma population and molecular-genetic analysis of the TMEM70 gene is sufficient for diagnosis without need of muscle biopsy in affected children. [ABSTRACT FROM AUTHOR]

Biallelic pathogenic variants in CLPP, encoding mitochondrial matrix peptidase ClpP, cause a rare autosomal recessive condition, Perrault syndrome type 3 (PRLTS3). It is characterized by primary ovarian insufficiency and early sensorineural hearing loss, often associated with progressive neurological deficits. Mouse models showed that accumulations of (i) its main protein interactor, the substrate-selecting AAA+ ATPase ClpX, (ii) mitoribosomes, and (iii) mtDNA nucleoids are the main cellular consequences of ClpP absence. However, the sequence of these events and their validity in human remain unclear. Here, we studied global proteome profiles to define ClpP substrates among mitochondrial ClpX interactors, which accumulated consistently in ClpP-null mouse embryonal fibroblasts and brains. Validation work included novel ClpP-mutant patient fibroblast proteomics. ClpX co-accumulated in mitochondria with the nucleoid component POLDIP2, the mitochondrial poly(A) mRNA granule element LRPPRC, and tRNA processing factor GFM1 (in mouse, also GRSF1). Only in mouse did accumulated ClpX, GFM1, and GRSF1 appear in nuclear fractions. Mitoribosomal accumulation was minor. Consistent accumulations in murine and human fibroblasts also affected multimerizing factors not known as ClpX interactors, namely, OAT, ASS1, ACADVL, STOM, PRDX3, PC, MUT, ALDH2, PMPCB, UQCRC2, and ACADSB, but the impact on downstream metabolites was marginal. Our data demonstrate the primary impact of ClpXP on the assembly of proteins with nucleic acids and show nucleoid enlargement in human as a key consequence. [ABSTRACT FROM AUTHOR]

Background: Autosomal recessive mutations in deoxyguanosine kinase (DGUOK) have been identified in the hepatocerebral form of mitochondrial DNA (mtDNA) depletion syndrome. Objectives: To describe the clinical spectrum of DGUOK-related mtDNA depletion syndrome in 6 children and to summarize the literature. Results: We identified pathogenic mutations in DGUOK in 6 children with the hepatocerebral form of mtDNA depletion syndrome. We describe the clinical, neuroradiologic, histologic, and genetic features in these children. All children showed severe hepatopathy, while involvement of other organs (skeletal muscle and brain) was variable. We identified 5 novel mutations (1 of them in 2 children) and 2 previously described mutations. Three different mutations affected the initial methionine, suggesting a mutational hot spot. One of our patients underwent liver transplantation; pathologic findings revealed (in addition to diffuse hepatopathy) a hepatocellular carcinoma, implying a possible link between mtDNA depletion syndrome and tumorigenesis. Conclusion: We studied 12 children with infantile hepatoencephalopathies and mtDNA depletion syndrome and found pathogenic DGUOK mutations in 6, suggesting that this gene defect is a frequent but not an exclusive cause of the hepatic form of mtDNA depletion syndrome. [ABSTRACT FROM AUTHOR]

We report a neonate with hypertrophic cardiomyopathy and lethal myeloproliferative disorder with excessively proliferating immature erythroid precursors infiltrating non-hematopoietic organs. Mutational analysis uncovered a germline mutation in the Noonan syndrome/LEOPARD syndrome (NS/LS) gene PTPN11. In conclusion, this case report suggests that congenital myeloproliferative disorders in association with germline PTPN11 mutations may affect the erythroid lineage. [ABSTRACT FROM AUTHOR]