Search Results (10)

Glutaric aciduria type 1 (GA1) is a rare inherited metabolic disease increasingly included in newborn screening (NBS) programs worldwide. Because of the broad biochemical spectrum of individuals with GA1 and the lack of reliable second-tier strategies, NBS for GA1 is still confronted with a high rate of false positives. In this study, we aim to increase the specificity of NBS for GA1 and, hence, to reduce the rate of false positives through machine learning methods. Therefore, we studied NBS profiles from 1,025,953 newborns screened between 2014 and 2023 at the Heidelberg NBS Laboratory, Germany. We identified a significant sex difference, resulting in twice as many false-positives male than female newborns. Moreover, the proposed digital-tier strategy based on logistic regression analysis, ridge regression, and support vector machine reduced the false-positive rate by over 90% compared to regular NBS while identifying all confirmed individuals with GA1 correctly. An in-depth analysis of the profiles revealed that in particular false-positive results with high associated follow-up costs could be reduced significantly. In conclusion, understanding the origin of false-positive NBS and implementing a digital-tier strategy to enhance the specificity of GA1 testing may significantly reduce the burden on newborns and their families from false-positive NBS results. Full article

Amino acid (AA)-related inherited metabolic disorders (IMDs) and urea cycle disorders (UCDs) require strict dietary management including foods low in protein such as fruits, vegetables and starchy roots. Despite this recommendation, there are limited data on the AA content of many of these foods. The aim of this study is to describe an analysis of the protein and AA content of a range of fruits, vegetables and starchy roots, specifically focusing on amino acids (AAs) relevant to AA-related IMDs such as phenylalanine (Phe), methionine (Met), leucine (Leu), lysine (Lys) and tyrosine (Tyr). AA analysis was performed using high-performance liquid chromatography (HPLC) on 165 food samples. Protein analysis was also carried out using the Dumas method. Foods were classified as either ‘Fruits’, ‘Dried fruits’, ‘Cruciferous vegetables’, ‘Legumes’, ‘Other vegetables’ or ‘Starchy roots’. ‘Dried fruits’ and ‘Legumes’ had the highest median values of protein, while ‘Fruits’ and ‘Cruciferous vegetables’ contained the lowest median results. ‘Legumes’ contained the highest and ‘Fruits’ had the lowest median values for all five AAs. Variations were seen in AA content for individual foods. The results presented in this study provide useful data on the protein and AA content of fruits, vegetables and starchy roots which can be used in clinical practice. This further expansion of the current literature will help to improve diet quality and metabolic control among individuals with AA-related IMDs and UCDs. Full article

Introduction: Dystonia can present in primary and secondary forms, depending on co-occurring symptoms and syndromic associations. In contrast to primary dystonia, secondary forms of dystonia are often associated with lesions in the putamen or globus pallidus. Such disorders are commonly neurodegenerative or neurometabolic conditions which produce varied neurologic as well as systemic manifestations other than dystonia. Chemo-denervation with botulinum toxin has been successfully used for focal or segmental dystonia. However, studies evaluating the effect of BoNT therapy on patients with secondary dystonia are sparse, given the heterogeneity in etiology and presentation. Methods: We present a series of patients with secondary dystonia who were managed with botulinum toxin therapy. Patients included in this series had a confirmed neurometabolic cause of dystonia. Results: A total of 14 patients, with ages ranging from 17 to 36 years, with disorders including Wilson’s disease, pantothenate kinase-associated neurodegeneration (PKAN), Niemann–Pick disease type C (NPC), glutaric aciduria type 1, Sanfilippo syndrome (Mucopolysaccharidosis Type IIIb), and GM2 gangliosidosis (Sandhoff disease) are presented. Most patients experienced a mild to moderate improvement in treated dystonia with benefits ranging from 6 to 12 weeks, with the median length of the benefits lasting approximately eight weeks, without any significant adverse effects. Conclusion: Although the secondary causes of dystonia are complex and diverse, our presented data and the available reports of the use of botulinum toxin support the conclusion that chemo-denervation plays an important role in symptom alleviation. Full article

Glutaric aciduria type 1 (GA-1) is a rare but treatable autosomal-recessive neurometabolic disorder of lysin metabolism caused by biallelic pathogenic variants in glutaryl-CoA dehydrogenase gene (GCDH) that lead to deficiency of GCDH protein. Without treatment, this enzyme defect causes a neurological phenotype characterized by movement disorder and cognitive impairment. Based on a comprehensive literature search, we established a large dataset of GCDH variants using the Leiden Open Variation Database (LOVD) to summarize the known genotypes and the clinical and biochemical phenotypes associated with GA-1. With these data, we developed a GCDH-specific variation classification framework based on American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines. We used this framework to reclassify published variants and to describe their geographic distribution, both of which have practical implications for the molecular genetic diagnosis of GA-1. The freely available GCDH-specific LOVD dataset provides a basis for diagnostic laboratories and researchers to further optimize their knowledge and molecular diagnosis of this rare disease. Full article

Organic acidurias are a heterogeneous group of rare inherited metabolic disorders (IMDs) caused by a deficiency of an enzyme or a transport protein involved in the intermediary metabolic pathways. These enzymatic defects lead to an accumulation of organic acids in different tissues and their subsequent excretion in urine. Organic acidurias include maple syrup urine disease, propionic aciduria, methylmalonic aciduria, isovaleric aciduria, and glutaric aciduria type 1. Clinical features vary between different organic acid disorders and may present with severe complications. An increasing number of women with rare IMDs are reporting successful pregnancy outcomes. Normal pregnancy causes profound anatomical, biochemical and physiological changes. Significant changes in metabolism and nutritional requirements take place during different stages of pregnancy in IMDs. Foetal demands increase with the progression of pregnancy, representing a challenging biological stressor in patients with organic acidurias as well as catabolic states post-delivery. In this work, we present an overview of metabolic considerations for pregnancy in patients with organic acidurias. Full article

Glutaric aciduria type I (GA-1) is a rare autosomal-recessive disorder of the degradation of the amino acids lysine and tryptophan caused by mutations of the GCDH gene encoding glutaryl-CoA-dehydrogenase. Newborn screening (NBS) for this condition is based on elevated levels of glutarylcarnitine (C5DC) in dried blood spots (DBS). Here we report four cases from three families in whom a correctly performed NBS did not detect the condition. Glutarylcarnitine concentrations were either normal (slightly below) or slightly above the cut-off. Ratios to other acylcarnitines were also not persistently elevated. Therefore, three cases were defined as screen negative, and one case was defined as normal, after a normal control DBS sample. One patient was diagnosed after an acute encephalopathic crisis, and the other three patients had an insidious onset of the disease. GA-1 was genetically confirmed in all cases. Despite extensive efforts to increase sensitivity and specificity of NBS for GA-1, by adjusting cut-offs and introducing various ratios, the biological diversity still leads to false-negative NBS results for GA-1. Full article

Glutaric aciduria type 1, homocystinuria, isovaleric acidaemia, long-chain hydroxyacyl CoA dehydrogenase deficiency and maple syrup urine disease are all inborn errors of metabolism that can be detected through newborn bloodspot screening. This evaluation was undertaken in 2013 to provide evidence to the UK National Screening Committee for the cost-effectiveness of including these five conditions in the UK Newborn Bloodspot Screening Programme. A decision-tree model with lifetable estimates of outcomes was built with the model structure and parameterisation informed by a systematic review and expert clinical judgment. A National Health Service/Personal Social Services perspective was used, and lifetime costs and quality-adjusted life years (QALYs) were discounted at 1.5%. Uncertainty in the results was explored using expected value of perfect information analysis methods together with a sensitivity analysis using the screened incidence rate in the UK from 2014 to 2018. The model estimates that screening for all the conditions is more effective and cost saving when compared to not screening for each of the conditions, and the results were robust to the updated incidence rates. The key uncertainties included the sensitivity and specificity of the screening test and the estimated costs and QALYs. Full article

In 2015, the newborn screening (NBS) programmes in England and Wales were expanded to include four additional disorders: Classical Homocystinuria, Isovaleric Acidemia, Glutaric Aciduria Type 1 and Maple Syrup Urine Disease, bringing the total number of analytes quantified to eight: phenylalanine, tyrosine, leucine, methionine, isovalerylcarnitine, glutarylcarnitine, octanoylcarnitine and decanoylcarnitine. Post-implementation, population data monitoring showed that inter-laboratory variation was greater than expected, with 90th centiles varying from 17% to 59%. We evaluated the effect of stable isotope internal standard (IS) used for quantitation on inter-laboratory variation. Four laboratories analysed routine screening samples (n > 101,820) using a common IS. Inter-laboratory variation was determined for the eight analytes and compared with results obtained using an in-house common IS (n > 102,194). A linear mixed-effects model was fitted to the data. Using a common IS mix reduced the inter-laboratory variation significantly (p < 0.05) for five analytes. For three analytes, the lack of significance was explained by use of individual laboratory “calibration factors”. For screening programmes where laboratories adhere to single analyte cut-off values (COVs), it is important that inter-laboratory variation is minimised, primarily to prevent false positive results. Whilst the use of a common IS helps achieve this, it is evident that instrument set-up also contributes to inter-laboratory variation. Full article

Glutaric aciduria type 1 (GA-1) is a cerebral organic aciduria characterized by striatal injury and progressive movement disorder. Nutrition management shifted from a general restriction of intact protein to targeted restriction of lysine and tryptophan. Recent guidelines advocate for a low-lysine diet using lysine-free, tryptophan-reduced medical foods. GA-1 guideline recommendations for dietary management of patients over the age of six are unclear, ranging from avoiding excessive intake of intact protein to counting milligrams of lysine intake. A 22–question survey on the nutrition management of GA-1 was developed with the goal of understanding approaches to diet management for patients identified by newborn screening under age six years compared to management after diet liberalization, as well as to gain insight into how clinicians define diet liberalization. Seventy-six responses (25% of possible responses) to the survey were received. Nutrition management with GA-1 is divergent among surveyed clinicians. There was congruency among survey responses to the guidelines, but there is still uncertainty about how to counsel patients on diet optimization and when diet liberalization should occur. Ongoing clinical research and better understanding of the natural history of this disease will help establish stronger recommendations from which clinicians can best counsel families. Full article

Incidental findings on newborn screening (NBS) are results that are not the target of screening within a given NBS program, but rather are found as a result of the screening and resulting diagnostic workup for that target. These findings may not have an immediate clinical impact on the newborn, but are sometimes an additional benefit of NBS programs and may be considered secondary targets of NBS programs. This work describes four case reports that had incidental findings on the NBS, which eventually led to the diagnosis of another metabolic disease instead of the one that was initially suspected. The first case was a new defect in the cationic amino acid transporter-2 (CAT-2), which was oriented as an arginase-1 deficiency in the newborn. The second case was a maternal glutaric aciduria type 1 (GA-1) that mimicked a carnitine transporter deficiency in the newborn. The third report was a case of lysinuric protein intolerance (LPI), which appeared as high levels of citrulline on the NBS. The fourth case was a mother with homocystinuria that was diagnosed during the biochemical study of vitamin B₁₂ status. All cases provide new or interesting data that will help guide differential diagnosis in the future. Full article