Use of guidelines improves the neurological outcome in glutaric aciduria type I

Digital-Tier Strategy Improves Newborn Screening for Glutaric Aciduria Type 1

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.

Disorders of organic acid metabolism and epilepsy

Epilepsy can be caused by a variety of causes, such as inborn errors of metabolism, organic acid disorders are the most significant type of metabolic disorders that cause seizures. The clinical manifestations of these diseases are generally nonspecific, and the types of seizures are different. Screening for multisystem clinical symptoms and identifying the underlying etiology are crucial for early treatment of epileptic seizures. This article provides a comprehensive summary of the pathogenesis, clinical features, diagnosis and treatment of epilepsy associated with organic acid metabolism disorders. Furthermore, relevant literature has also been reviewed to assist clinicians in the diagnosis of cases characterized by the coexistence of multisystemic symptoms and epileptic manifestations.

Megalencephaly: Classification, Genetic Causes, and Related Syndromes

Megalencephaly is a developmental disorder due to an abnormal neuronal proliferation and migration during intrauterine or postnatal brain development that leads to cerebral overgrowth and neurological dysfunction. This cerebral overgrowth may affect the whole encephalon or only a region; when it involves one hemisphere it is referred to as hemimegalencephaly. Megalencephaly presents with a head circumference measurement of 2 standard deviations above the average measure for age. This group of disorders is clinically characterized by early onset and refractory to therapy epilepsy, neurodevelopmental disorders, behavioral problems, and autism spectrum disorder. Syndromic forms of megalencephaly should be considered when associated with other congenital abnormalities. Megalencephaly in fact could be associated with segmental overgrowth and cutaneous/vascular abnormalities (i.e., Proteus syndrome, CLOVES [congenital lipomatous overgrowth, vascular malformations, epidermal naevi, scoliosis, and/ or skeletal abnormalities] syndrome, Klippel-Trenaunay syndrome, megalencephaly-capillary malformation-polymicrogyria syndrome , megalencephaly-postaxial polydactyly-polymicrogyria-hydrocephalus syndrome, etc.) or generalized overgrowth (i.e., Weaver or Beckwith-Wiedemann syndrome) as well as with nanism in achondroplasia where megalencephaly is associated with disproportionate short stature, primary skeletal dysplasia, characteristic facies (prominent forehead, flat nasal bridge), narrow chest, and normal intelligence. It is possible to identify three main groups of disorders associated with megalencephaly: idiopathic or benign, metabolic, and anatomic. The idiopathic (benign) form indicates an abnormal increased head circumference in absence of neurological impairment, such as in benign familial megalencephaly. In metabolic megalencephaly (such as in organic acid disorders, metabolic leukoencephalopathies, or lysosomal diseases) there is an increase of different constituents that increase the size of the brain, whereas in the anatomical form there are underlying genetic causes. Neuroimaging is crucial for diagnosis, as it can reveal a generalized brain growth or a segmental one and possible specific frameworks associated. In all these conditions it is necessary to identify possible microdeletion-microduplication by chromosomal arrays.

[Evaluation and optimization of newborn screening by structured long-term follow-up-using the example of inherited metabolic diseases]

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.

Novel utilization of deep brain stimulation in the pedunculopontine nucleus with globus pallidus internus for treatment of childhood-onset dystonia

Introduction

Deep brain stimulation (DBS) is a well-documented therapy for dystonia utilized in many adult and pediatric movement disorders. Pedunculopontine nucleus (PPN) has been investigated as a DBS target primarily in adult patients with dystonia or dyskinesias from Parkinson's disease, showing improvement in postural instability and gait dysfunction. Due to the difficulty in targeting PPN using standard techniques, it is not commonly chosen as a target for adult or pediatric pathology. There is no current literature describing the targeting of PPN in DBS for childhood-onset dystonia.

Methods

Two pediatric and one young adult patient with childhood-onset dystonia who underwent DBS implantation at our institution were identified. Patient 1 has Mitochondrial Enoyl CoA Reductase Protein-Associated Neurodegeneration (MEPAN) syndrome. Patient 2 has Glutaric Aciduria Type 1 (GA1). Patient 3 has atypical pantothenate kinase-associated neurodegeneration (PKAN). PPN was identified as a potential target for these patients due to axial or orofacial dystonia. Pre- and post-operative videos taken as part of routine clinical assessments were evaluated and scored on the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Barry-Albright Dystonia Scale (BADS). All patients had permanent electrodes placed bilaterally in PPN and globus pallidus internus (GPi). A Likert scale on quality of life was also obtained from the patient/parents as applicable.

Results

Significant programming was necessary over the first 3-12 months to optimize patients' response to stimulation. All patients experienced at least a 34% improvement in the BFMDRS score. Patients 2 and 3 also experienced an over 30% improvement in BADS score. All patients/parents appreciated improvement in quality of life postoperatively.

Discussion

Deep brain stimulation in PPN was safely and successfully used in two pediatric patients and one young adult patient with childhood-onset dystonia. These patients showed clinically significant improvements in BFMDRS scoring post operatively. This represents the first reported DBS targeting of PPN in pediatric patients, and suggests that PPN is a possible target for pediatric-onset dystonia with axial and orofacial symptoms that may be refractory to traditional pallidal stimulation alone.

Catching the Culprit: How Chorea May Signal an Inborn Error of Metabolism

Background

Movement disorders, particularly chorea, are uncommon in inborn errors of metabolism, but their identification is essential for improved clinical outcomes. In this context, comprehensive descriptions of movement disorders are limited and primarily derived from single cases or small patient series, highlighting the need for increased awareness and additional research in this field.

Methods

A systematic review was conducted using the MEDLINE database and GeneReviews. The search included studies on inborn errors of metabolism associated with chorea, athetosis, or ballismus. The review adhered to PRISMA guidelines.

Results

The systematic review analyzed 76 studies out of 2350 records, encompassing the period from 1964 to 2022. Chorea was observed in 90.1% of the 173 patients, followed by athetosis in 5.7%. Various inborn errors of metabolism showed an association with chorea, with trace elements and metals being the most frequent. Cognitive and developmental abnormalities were common in the cohort. Frequent neurological features included seizures, dysarthria, and optic atrophy, whereas non-neurological features included, among others, facial dysmorphia and failure to thrive. Neuroimaging and biochemical testing played crucial roles in aiding diagnosis, revealing abnormal findings in 34.1% and 47.9% of patients, respectively. However, symptomatic treatment efficacy for movement disorders was limited.

Discussion

This study emphasizes the complexities of chorea in inborn errors of metabolism. A systematic approach with red flags, biochemical testing, and neuroimaging is required for diagnosis. Collaboration between neurologists, geneticists, and metabolic specialists is crucial for improving early detection and individualized treatment. Utilizing genetic testing technologies and potential therapeutic avenues can aid in the improvement of patient outcomes.

Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey

Background

Cerebral organic acid disorders are progressive neurometabolic diseases characterized by neurologic dysfunction. Glutaric aciduria type I (GA-I) and L-2-hydroxyglutaric aciduria (L2HGA) are the main cerebral organic acid disorders. They are both classified as, and it is suggested that these two disorders may share a common metabolic pathway. Current treatment strategies are based on levocarnitine, vitamin B2, and diet. Recent guidelines recommend a lysine-restricted diet up to six years of age, but there is no consensus for patients over the age of six. Vitamin B2 is exists in the blood as riboflavin and its cofactors, flavin mononucleotide and flavin adenine dinucleotide (FAD). FAD, the cofactor of L2HGD, accelerates the conversion of L-2-hydoxy glutarate to alpha-ketoglutarate. Levocarnitine stimulates the formation and excretion of derivatives of glutaric acid. Also, lysine-associated organic acidurias some results provide principal proof for the beneficial effects of riboflavin in GA-I. It has been previously reported that combination therapy with riboflavin and levocarnitine is effective for L2HGA as well as GA-I. Riboflavin and levocarnitine have been reported to improve not only clinical symptoms but also urinary 2-HGA levels. In our study, we aimed to evaluate the effect of the current treatment strategies and genotype on urinary metabolites and IQ scores in GA-I and L2HGA patients.

Methods

The presented retrospective multicenter study included patients followed up in Diyarbakir Children's Hospital and Izmir Katip Celebi University Faculty of Medicine, Division of Pediatric Metabolism. Between 2016 and 2021, we retrospectively evaluated 35 patients with confirmed diagnosis of GA-I and L-2HGA. We analyzed the clinical, biochemical, neuroradiological, molecular data and treatment of the patients. The follow-up period was every 2 months until 12 months old, every 3 months until 6 years of age, and every 6 months thereafter. Therapy monitoring was undertaken during follow-up visits that included evaluation of clinical parameters, laboratory parameters, and dietary consumption records. Denver II was applied in order to evaluate children aged 0-6 years in terms of development. Patients between 6 and 16 years of age were evaluated using the Wechsler Intelligence Scale for Children-Revised.

Results

We identified 25 with GA-I and 10 with L2HGA. The most common clinical symptoms were developmental delay, intellectual disability, and movement disorders. Behavioural problems were more common in L2HGA than in GA-I patients. In the same family, there were patients with severe developmental delay despite early diagnosis and treatment and individuals with normal IQ scores. In our study group, we used diet (lysine restricted or protein controlled), levocarnitine and vitamin B2 for GA-I patients. The mean urinary glutaric acid levels were decreased with treatment in GA-I patients. Group I consisted of 14/25 patients receiving lysine restricted diet and levocarnitine, Group II (8/25) received protein-controlled diet and levocarnitine. Group III (3/25) patients whom had p.Pro248Leu (P248L) variant, received riboflavin in combination with protein-controlled diet and levocarnitine. When we evaluated according to the treatment groups, a significant decrease was observed in urinary glutaric acid levels in group I. But there were no significant difference in Group II and III. The patients with c.1018C > T variant in GCDH gene had higher pre-treatment urinary metabolites and significant reduction in urinary metabolites with treatment was detected. In L2HGA patients, we used levocarnitine and vitamin B2. In all L2HGA patients, there was a significant decrease in the mean urinary 2- hydoxy glutarate with treatment. However, there was no significant difference between the c.164G > A and c.1115delT variants. The mean pre- and post-treatment IQ scores of GA-I patients, no significant difference was observed. Relative neurologic improvement was seen in three L2HGA patients. We found two novel variants, including the c.221A > G (p.Tyr74Cys) in the GCDH gene and the c.738 + 5A > G splice variant in the L2HGDH gene.

Conclusions

Glutaric aciduria type I and L2HGA are the most common cerebral organic acidurias. Early and correct diagnosis is crucial. Poor prognosis based on metabolic crises and progressive deterioration still appears. In countries where newborn screening is not performed, a clinical suspicion index is required for cerebral organic aciduria. GA-I and L-2HGA are difficult to examine by medical evidence standards because of the small sample size, regional differences in newborn screening, and medical care limits. More clinical studies are needed to identify effective treatments. However, the significant decrease in urinary glutaric acid levels after treatment in patients on lysine-restricted diet raises the question of whether lysine-restricted diet should be continued after six years of age. We also reported our experience in order to contribute to the literature.

Biochemical and molecular features of chinese patients with glutaric acidemia type 1 from Fujian Province, southeastern China

BACKGROUND

Glutaric acidemia type 1 (GA1) is a rare autosomal recessive inherited metabolic disorder caused by variants in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCDH). The estimated prevalence of GA1 and the mutational spectrum of the GCDH gene vary widely according to race and region. The aim of this study was to assess the acylcarnitine profiles and genetic characteristics of patients with GA1 in Fujian Province, southeastern China.

RESULTS

From January 2014 to December 2022, a total of 1,151,069 newborns (631,016 males and 520,053 females) were screened using MS/MS in six newborn screening (NBS) centers in Fujian Province and recruited for this study. Through NBS, 18 newborns (13 females and 5 males) were diagnosed with GA1. Thus, the estimated incidence of GA1 was 1 in 63,948 newborns in Fujian province. In addition, 17 patients with GA1 were recruited after clinical diagnosis. All but one patient with GA1 had a remarkable increase in glutarylcarnitine (C5DC) concentrations. The results of urinary organic acid analyses in 33 patients showed that the concentration of glutaric acid (GA) increased in all patients. The levels of C5DC and GA in patients identified via NBS were higher than those in patients identified via clinical diagnosis (P < 0.05). A total of 71 variants of 70 alleles were detected in patients with GA1, with 19 different pathogenic variants identified. The three most prevalent variants represented 73.23% of the total and were c.1244-2 A > C, p.(?) (63.38%), c.1261G > A, p.Ala421Thr (5.63%), and c.406G > T, p.Gly136Cys (4.22%). The most abundant genotype observed was c.[1244-2 A > C]; [1244-2 A > C] (18/35, 52.43%) and its phenotype corresponded to high excretors (HE, GA > 100 mmol/mol Cr).

CONCLUSIONS

In conclusion, we investigated the biochemical and molecular features of 35 unrelated patients with GA1. C5DC concentrations in dried blood spots and urinary GA are effective indicators for a GA1 diagnosis. Our study also identified a GCDH variant spectrum in patients with GA1 from Fujian Province, southeastern China. Correlation analysis between genotypes and phenotypes provides preliminary and valuable information for genetic counseling and management.

Deep brain stimulation and intrathecal/intraventricular baclofen for glutaric aciduria type 1: A scoping review, individual patient data analysis, and clinical trials review

Glutaric aciduria type 1 (GA1) is an autosomal recessive disease frequently leading to dystonia. Deep brain stimulation (DBS), intrathecal baclofen (ITB), and intraventricular baclofen (IVB) are the current interventional treatment options for refractory dystonia. We performed a scoping review, individual patient data (IPD) analysis, and clinical trials review to summarize the existing literature on these interventions in this population, characterize outcomes, and suggest directions for future investigation. PubMed, Embase, and Scopus were searched following PRISMA guidelines. IPD were extracted from studies providing IPD for GA1 patients. ClinicalTrials.gov was reviewed. Of 139 articles, 7 studies with 10 patients were included. In study-level data, 2/4 (50.0%) DBS studies found no improvement in dystonia and 3/3 (100%) on baclofen found decreased dystonia and enteral medication regimen. In the IPD analysis, four studies with 5 patients (2 IVB, 2 DBS, 1 ITB) were included. The average percent reduction in dystonia was 29.9% ± 32.5% (median:18%, IQR:18%-29.2%). Function improved in 4 (80.0%) patients. All patients with reported changes in enteral dystonia-related medication regimen (3/3, 100%) reported reduction in medication usage. No patients (0%) had perioperative complications. Mean follow-up length was 14.8 ± 12.2 months. No interventional clinical trials were found. ITB, IVB, and DBS represent present neuromodulatory approaches for the treatment of GA1. ITB and IVB reduce dystonia, while DBS has a heterogeneous effect. ITB and IVB improved function and reduced enteral medication regimens. These findings must be viewed with caution considering limited data and a serious risk of bias. Further large-scale studies are necessary to determine indications for ITB, IVB, and DBS and elucidate treatment algorithms.

Two novel compound heterozygous variants of the GCDH gene in two Chinese families with glutaric acidaemia type I identified by high-throughput sequencing and a literature review

Autosomal recessive glutaric acidaemia type I (GA-I) is a rare hereditary metabolic disease characterized by increased organic acids and neurologic symptoms. Although numerous variants in the GCDH gene have been identified to be connected with the pathogenesis of GA-I, the relationship between genotype and phenotype remains uncertain. In this study, we evaluated genetic data for two GA-I patients from Hubei, China, and we reviewed the previous research findings to clarify the genetic heterogeneity of GA-I and identify the potential causative variants. After we extracted genomic DNA from peripheral blood samples obtained from two unrelated Chinese families, we used target capture high-throughput sequencing combined with Sanger sequencing to determine likely pathogenic variants in the two probands. Electronic databases were also searched for the literature review. The genetic analysis revealed two compound heterozygous variants in the GCDH gene expected to lead to GA-I in the two probands (P1 and P2), with P1 carrying two known variants (c.892G > A/p. A298T and c.1244-2A > C/IVS10-2A > C) and P2 harbouring two novel variants (c.370G > T/p.G124W and c.473A > G/p.E158G). In the literature review, the most common alleles in low excretors (i.e., individuals with low excretion of GA) were R227P, V400M, M405V, and A298T, with variation in the severity of clinical phenotypes. Overall, we identified two novel GCDH gene candidate pathogenic variants in a Chinese patient, enriching the GCDH gene mutational spectrum and providing a solid foundation for the early diagnosis of GA-I patients with low excretion.

Drosophila as a diet discovery tool for treating amino acid disorders

Amino acid disorders (AADs) are a large group of rare inherited conditions that collectively impact one in 6500 live births, often resulting in rapid neurological decline and death during infancy. For several AADs, including phenylketonuria, dietary modification prevents physiological deterioration and ameliorates symptoms. Despite this remarkable potential for treatment success, dietary therapy for most AADs remains largely unexplored. Although animal models have provided novel insights into AAD mechanisms, few have been used for therapeutic diet discovery. Here, we find that of all the animal models, Drosophila is particularly well suited for nutrigenomic disease modelling, having amino acid pathways conserved with humans, exceptional genetic tractability, and the unique availability of a synthetic customisable diet.

How guideline development has informed clinical research for organic acidurias (et vice versa)

Organic acidurias, such as glutaric aciduria type 1 (GA1), methylmalonic (MMA), and propionic aciduria (PA) are a prominent group of inherited metabolic diseases involving accumulation of eponymous metabolites causing endogenous intoxication. For all three conditions, guidelines for diagnosis and management have been developed and revised over the last years, resulting in three revisions for GA1 and one revision for MMA/PA. The process of clinical guideline development in rare metabolic disorders is challenged by the scarcity and limited quality of evidence available. The body of literature is often fragmentary and where information is present, it is usually derived from small sample sizes. Therefore, the development of guidelines for GA1 and MMA/PA was initially confronted with a poor evidence foundation that hindered formulation of concrete recommendations in certain contexts, triggering specific research projects and initiation of longitudinal, prospective observational studies using patient registries. Reversely, these observational studies contributed to evaluate the value of newborn screening, phenotypic diversities, and treatment effects, thus significantly improving the quality of evidence and directly influencing formulation and evidence levels of guideline recommendations. Here, we present insights into interactions between guideline development and (pre)clinical research for GA1 and MMA/PA, and demonstrate how guidelines gradually improved from revision to revision. We describe how clinical studies help to unravel the relative impact of therapeutic interventions on outcome and conclude that despite new and better quality of research data over the last decades, significant shortcomings of evidence regarding prognosis and treatment remain. It appears that development of clinical guidelines can directly help to guide research, and vice versa.

Recommendations for diagnosing and managing individuals with glutaric aciduria type 1: Third revision

Glutaric aciduria type 1 is a rare inherited neurometabolic disorder of lysine metabolism caused by pathogenic gene variations in GCDH (cytogenic location: 19p13.13), resulting in deficiency of mitochondrial glutaryl-CoA dehydrogenase (GCDH) and, consequently, accumulation of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid and glutarylcarnitine detectable by gas chromatography/mass spectrometry (organic acids) and tandem mass spectrometry (acylcarnitines). Depending on residual GCDH activity, biochemical high and low excreting phenotypes have been defined. Most untreated individuals present with acute onset of striatal damage before age 3 (to 6) years, precipitated by infectious diseases, fever or surgery, resulting in irreversible, mostly dystonic movement disorder with limited life expectancy. In some patients, striatal damage develops insidiously. In recent years, the clinical phenotype has been extended by the finding of extrastriatal abnormalities and cognitive dysfunction, preferably in the high excreter group, as well as chronic kidney failure. Newborn screening is the prerequisite for pre-symptomatic start of metabolic treatment with low lysine diet, carnitine supplementation and intensified emergency treatment during catabolic episodes, which, in combination, have substantially improved neurologic outcome. In contrast, start of treatment after onset of symptoms cannot reverse existing motor dysfunction caused by striatal damage. Dietary treatment can be relaxed after the vulnerable period for striatal damage, that is, age 6 years. However, impact of dietary relaxation on long-term outcomes is still unclear. This third revision of evidence-based recommendations aims to re-evaluate previous recommendations (Boy et al., J Inherit Metab Dis, 2017;40(1):75-101; Kolker et al., J Inherit Metab Dis 2011;34(3):677-694; Kolker et al., J Inherit Metab Dis, 2007;30(1):5-22) and to implement new research findings on the evolving phenotypic diversity as well as the impact of non-interventional variables and treatment quality on clinical outcomes.

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.

Glutaric aciduria type 1: Diagnosis, clinical features and long-term outcome in a large cohort of 34 Irish patients

Glutaric aciduria type 1 (GA1) is a rare neurometabolic disorder that can lead to encephalopathic crises and severe dystonic movement disorders. Adherence to strict dietary restriction, in particular a diet low in lysine, carnitine supplementation and emergency treatment in pre-symptomatic patients diagnosed by high-risk screen (HRS) or newborn screen (NBS) leads to a favourable outcome. We present biochemical and clinical characteristics and long-term outcome data of 34 Irish patients with GA1 aged 1-40 years. Sixteen patients were diagnosed clinically, and 17 patients by HRS, prior to introduction of NBS for GA1 in the Republic of Ireland in 2018. One patient was diagnosed by NBS. Clinical diagnosis was at a median of 1 year (range 1 month to 8 years) and by HRS was at a median of 4 days (range 3 days to 11 years). 14/18 (77.8%) diagnosed by HRS or NBS had neither clinical manifestations nor radiological features of GA1, or had radiological features only, compared to 0/16 (0%) diagnosed clinically (p < 0.001). Patients diagnosed clinically who survived to school-age were more likely to have significant cerebral palsy and dystonia (7/11; 63.6% vs. 0/13; 0%, p < 0.001). They were less likely to be in mainstream school versus the HRS group (5/10; 50% vs. 12/13; 92.3%; p = 0.012). Clinical events occurring after 6 years of age were unusual, but included spastic diplegia, thalamic haemorrhage, Chiari malformation, pituitary hormone deficiency and epilepsy. The exact aetiology of these events is unclear.

Glutaric Acidemia, Pathogenesis and Nutritional Therapy

Glutaric acidemia (GA) are heterogeneous, genetic diseases that present with specific catabolic deficiencies of amino acid or fatty acid metabolism. The disorders can be divided into type I and type II by the occurrence of different types of recessive mutations of autosomal, metabolically important genes. Patients of glutaric acidemia type I (GA-I) if not diagnosed very early in infanthood, experience irreversible neurological injury during an encephalopathic crisis in childhood. If diagnosed early the disorder can be treated successfully with a combined metabolic treatment course that includes early catabolic emergency treatment and long-term maintenance nutrition therapy. Glutaric acidemia type II (GA- II) patients can present clinically with hepatomegaly, non-ketotic hypoglycemia, metabolic acidosis, hypotonia, and in neonatal onset cardiomyopathy. Furthermore, it features adult-onset muscle-related symptoms, including weakness, fatigue, and myalgia. An early diagnosis is crucial, as both types can be managed by simple nutraceutical supplementation. This review discusses the pathogenesis of GA and its nutritional management practices, and aims to promote understanding and management of GA. We will provide a detailed summary of current clinical management strategies of the glutaric academia disorders and highlight issues of nutrition therapy principles in emergency settings and outline some specific cases.

Rare Disease Registries Are Key to Evidence-Based Personalized Medicine: Highlighting the European Experience

Rare diseases, such as inherited metabolic diseases, have been identified as a health priority within the European Union more than 20 years ago and have become an integral part of EU health programs and European Reference Networks. Having the potential to pool data, to achieve sufficient sample size, to overcome the knowledge gap on rare diseases and to foster epidemiological and clinical research, patient registries are recognized as key instruments to evidence-based medicine for individuals with rare diseases. Patient registries can be used for multiple purposes, such as (1) describing the natural history and phenotypic diversity of rare diseases, (2) improving case definition and indication to treat, (3) identifying strategies for risk stratification and early prediction of disease severity (4), evaluating the impact of preventive, diagnostic, and therapeutic strategies on individual health, health economics, and the society, and (5) informing guideline development and policy makers. In contrast to clinical trials, patient registries aim to gather real-world evidence and to achieve generalizable results based on patient cohorts with a broad phenotypic spectrum. In order to develop a consistent and sustained framework for rare disease registries, uniform core principles have been formulated and have been formalized through the European Rare Disease Registration Infrastructure. Adherence to these core principles and compliance with the European general data protection regulations ensures that data collected and stored in patient registries can be exchanged and pooled in a protected environment. To illustrate the benefits and limitations of patient registries on rare disease research this review focuses on inherited metabolic diseases.

Subdural hematoma in glutaric aciduria type 1: High excreters are prone to incidental SDH despite newborn screening

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.

The outcome of 41 Late-Diagnosed Turkish GA-1 Patients: A Candidate for the Turkish NBS

BACKGROUND

Glutaric aciduria type 1(GA-1) is an inherited cerebral organic aciduria. Untreated patients with GA-1 have a risk of acute encephalopathic crises during the first 6 years of life. In so far as GA-1 desperately does not exist in Turkish newborn screening (NBS) program, most patients in our study were late-diagnosed.

METHOD

This study included 41 patients diagnosed with acylcarnitine profile, urinary organic acids, mutation analyses in the symptomatic period. We presented with clinical, neuroradiological, and molecular data of our 41 patients.

RESULTS

The mean age at diagnosis was 14.8 ± 13.9 (15 days to 72 months) and, high blood glutaconic acid, glutarylcarnitine and urinary glutaric acid (GA) levels in 41 patients were revealed. Seventeen different mutations in the glutaryl-CoA dehydrogenase gene were identified, five of which were novel. The patients, most of whom were late-diagnosed, had a poor neurological outcome. Treatment strategies made a little improvement in dystonia and the frequency of encephalopathic attacks.

CONCLUSION

All GA-1 patients in our study were severely affected since they were late-diagnosed, while others show that GA-1 is a treatable metabolic disorder if it is diagnosed with NBS. This study provides an essential perspective of the severe impact on GA-1 patients unless it is diagnosed with NBS. We immediately advocate GA-1 to be included in the Turkish NBS.

Protective effects of L-carnitine on behavioral alterations and neuroinflammation in striatum of glutaryl-COA dehydrogenase deficient mice

Glutaric acidemia type 1 (GA1) is caused by glutaryl-CoA dehydrogenase deficiency that leads to a blockage in the metabolic route of the amino acids lysine and tryptophan and subsequent accumulation of glutaric acid (GA), 3-hydroxyglutaric acids and glutarylcarnitine (C5DC). Patients predominantly manifest neurological symptoms, associated with acute striatal degeneration, as well as progressive cortical and striatum injury whose pathogenesis is not yet fully established. Current treatment includes protein/lysine restriction and l-carnitine supplementation of (L-car). The aim of this work was to evaluate behavior parameters and pro-inflammatory factors (cytokines IL-1β, TNF-α and cathepsin-D levels), as well as the anti-inflammatory cytokine IL10 in striatum of knockout mice (Gcdh-/-) and wild type (WT) mice submitted to a normal or a high Lys diet. The potential protective effects of L-car treatment on these parameters were also evaluated. Gcdh-/- mice showed behavioral changes, including lower motor activity (decreased number of crossings) and exploratory activity (reduced number of rearings). Also, Gcdh-/- mice had significantly higher concentrations of glutarylcarnitine (C5DC) in blood and cathepsin-D (CATD), interleukin IL-1β and tumor factor necrosis alpha (TNF-α) in striatum than WT mice. Noteworthy, L-car treatment prevented most behavioral alterations, normalized CATD levels and attenuated IL-1β levels in striatum of Gcdh-/- mice. Finally, IL-1β was positively correlated with CATD and C5DC levels and L-car was negatively correlated with CATD. Our results demonstrate behavioral changes and a pro-inflammatory status in striatum of the animal model of GA1 and, most importantly, L-car showed important protective effects on these alterations.

The biochemical subtype is a predictor for cognitive function in glutaric aciduria type 1: a national prospective follow-up study

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.

Clinical Utility of Rapid Exome Sequencing Combined With Mitochondrial DNA Sequencing in Critically Ill Pediatric Patients With Suspected Genetic Disorders

Genetic disorders are a frequent cause of hospitalization, morbidity and mortality in pediatric patients, especially in the neonatal or pediatric intensive care unit (NICU/PICU). In recent years, rapid genome-wide sequencing (exome or whole genome sequencing) has been applied in the NICU/PICU. However, mtDNA sequencing is not routinely available in rapid genetic diagnosis programs, which may fail to diagnose mtDNA mutation-associated diseases. Herein, we explored the clinical utility of rapid exome sequencing combined with mtDNA sequencing in critically ill pediatric patients with suspected genetic disorders. Rapid clinical exome sequencing (CES) was performed as a first-tier test in 40 critically ill pediatric patients (aged from 6 days to 15 years) with suspected genetic conditions. Blood samples were also collected from the parents for trio analysis. Twenty-six patients presented with neuromuscular abnormalities or other systemic abnormalities, suggestive of suspected mitochondrial diseases or the necessity for a differential diagnosis of other diseases, underwent rapid mtDNA sequencing concurrently. A diagnosis was made in 18 patients (45.0%, 18/40); three cases with de novo autosomal dominant variants, ten cases with homozygous or compound heterozygous variants, three cases with hemizygous variants inherited from mother, three cases with heterozygous variants inherited from either parent, and one case with a mtDNA mutation. The 18 patients were diagnosed with metabolic (n = 7), immunodeficiency (n = 4), cardiovascular (n = 2), neuromuscular (n = 2) disorders, and others. Genetic testing reports were generated with a median time of 5 days (range, 3–9 days). Thirteen patients that were diagnosed had an available medical treatment and resulted in a positive outcome. We propose that rapid exome sequencing combined with mitochondrial DNA sequencing should be available to patients with suspected mitochondrial diseases or undefined clinical features necessary for making a differential diagnosis of other diseases.

The low excretor phenotype of glutaric acidemia type I is a source of false negative newborn screening results and challenging diagnoses

BACKGROUND

Glutaric acidemia type I (GA1) is an organic acidemia that is often unrecognized in the newborn period until patients suffer an acute encephalopathic crisis, which can be mistaken for nonaccidental trauma. Presymptomatic identification of GA1 patients is possible by newborn screening (NBS). However, the biochemical "low-excretor" (LE) phenotype with nearly normal levels of disease metabolites can be overlooked, which may result in untreated disease and irreversible neurological sequelae. The LE phenotype is also a potential source of false negative (FN) NBS results that merits further investigation.

METHODS

Samples from six LE GA1 patients were analyzed by biochemical and molecular methods and newborn screen outcomes were retrospectively investigated.

RESULTS

Five LE GA1 patients were identified that had normal NBS results and three of these presented clinically with GA1 symptoms. One additional symptomatic patient was identified who did not undergo screening. Semiquantitative urine organic acid analysis was consistent with a GA1 diagnosis in two (33%) of the six patients, while plasma glutarylcarnitine was elevated in four (67%) of the six and urine glutarylcarnitine was elevated in four (80%) of five patients. Five GCDH variants were identified in these patients; three of which have not been previously linked to the biochemical LE phenotype.

CONCLUSIONS

The data presented here raise awareness of potential FN NBS results for LE GA1 patients. The LE phenotype is not protective against adverse clinical outcomes, and the possibility of FN NBS results calls for high vigilance amongst clinicians, even in the setting of a normal NBS result.

Glutaric Aciduria Type I Missed by Newborn Screening: Report of Four Cases from Three Families

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.

Impact of interventional and non-interventional variables on anthropometric long-term development in glutaric aciduria type 1: A national prospective multi-centre study

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.

Organic acidurias: Major gaps, new challenges, and a yet unfulfilled promise

Organic acidurias (OADs) comprise a biochemically defined group of inherited metabolic diseases. Increasing awareness, reliable diagnostic work-up, newborn screening programs for some OADs, optimized neonatal and intensive care, and the development of evidence-based recommendations have improved neonatal survival and short-term outcome of affected individuals. However, chronic progression of organ dysfunction in an aging patient population cannot be reliably prevented with traditional therapeutic measures. Evidence is increasing that disease progression might be best explained by mitochondrial dysfunction. Previous studies have demonstrated that some toxic metabolites target mitochondrial proteins inducing synergistic bioenergetic impairment. Although these potentially reversible mechanisms help to understand the development of acute metabolic decompensations during catabolic state, they currently cannot completely explain disease progression with age. Recent studies identified unbalanced autophagy as a novel mechanism in the renal pathology of methylmalonic aciduria, resulting in impaired quality control of organelles, mitochondrial aging and, subsequently, progressive organ dysfunction. In addition, the discovery of post-translational short-chain lysine acylation of histones and mitochondrial enzymes helps to understand how intracellular key metabolites modulate gene expression and enzyme function. While acylation is considered an important mechanism for metabolic adaptation, the chronic accumulation of potential substrates of short-chain lysine acylation in inherited metabolic diseases might exert the opposite effect, in the long run. Recently, changed glutarylation patterns of mitochondrial proteins have been demonstrated in glutaric aciduria type 1. These new insights might bridge the gap between natural history and pathophysiology in OADs, and their exploitation for the development of targeted therapies seems promising.

Developments in evidence creation for treatments of inborn errors of metabolism

Inborn errors of metabolism (IEM) represent the first group of genetic disorders, amenable to causal therapies. In addition to traditional medical diet and cofactor treatments, new treatment strategies such as enzyme replacement and small molecule therapies, solid organ transplantation, and cell-and gene-based therapies have become available. Inherent to the rare nature of the single conditions, generating high-quality evidence for these treatments in clinical trials and under real-world conditions has been challenging. Guidelines developed with standardized methodologies have contributed to improve the practice of care and long-term clinical outcomes. Adaptive trial designs allow for changes in sample size, group allocation and trial duration as the trial proceeds. n-of-1 studies may be used in small sample sized when participants are clinically heterogeneous. Multicenter observational and registry-based clinical trials are promoted via international research networks. Core outcome and standard data element sets will enhance comparative analysis of clinical trials and observational studies. Patient-centered outcome-research as well as patient-led research initiatives will further accelerate the development of therapies for IEM.

Cyclic Vomiting Syndrome in Children

Cyclic Vomiting Syndrome (CVS) is an underdiagnosed episodic syndrome characterized by frequent hospitalizations, multiple comorbidities, and poor quality of life. It is often misdiagnosed due to the unappreciated pattern of recurrence and lack of confirmatory testing. CVS mainly occurs in pre-school or early school-age, but infants and elderly onset have been also described. The etiopathogenesis is largely unknown, but it is likely to be multifactorial. Recent evidence suggests that aberrant brain-gut pathways, mitochondrial enzymopathies, gastrointestinal motility disorders, calcium channel abnormalities, and hyperactivity of the hypothalamic-pituitary-adrenal axis in response to a triggering environmental stimulus are involved. CVS is characterized by acute, stereotyped and recurrent episodes of intense nausea and incoercible vomiting with predictable periodicity and return to baseline health between episodes. A distinction with other differential diagnoses is a challenge for clinicians. Although extensive and invasive investigations should be avoided, baseline testing toward identifying organic causes is recommended in all children with CVS. The management of CVS requires an individually tailored therapy. Management of acute phase is mainly based on supportive and symptomatic care. Early intervention with abortive agents during the brief prodromal phase can be used to attempt to terminate the attack. During the interictal period, non-pharmacologic measures as lifestyle changes and the use of reassurance and anticipatory guidance seem to be effective as a preventive treatment. The indication for prophylactic pharmacotherapy depends on attack intensity and severity, the impairment of the QoL and if attack treatments are ineffective or cause side effects. When children remain refractory to acute or prophylactic treatment, or the episode differs from previous ones, the clinician should consider the possibility of an underlying disease and further mono- or combination therapy and psychotherapy can be guided by accompanying comorbidities and specific sub-phenotype. This review was developed by a joint task force of the Italian Society of Pediatric Gastroenterology Hepatology and Nutrition (SIGENP) and Italian Society of Pediatric Neurology (SINP) to identify relevant current issues and to propose future research directions on pediatric CVS.

Inconsistencies in the Nutrition Management of Glutaric Aciduria Type 1: An International Survey

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.

Orthopaedic manifestations of glutaric acidemia Type 1

PURPOSE

Glutaric acidemia type 1 (GA1), a rare hereditary metabolic disease caused by biallelic mutations of GCDH, can result in acute or insidious striatal degeneration within the first few years of life. We reviewed the orthopaedic sequelae and management of 114 neurologically injured patients with a confirmed molecular diagnosis of GA1.

METHODS

We performed a retrospective chart review spanning 28 years identifying 114 GA1 patients, most from the Old Order Amish population of Lancaster County, Pennsylvania, who were homozygous for a pathogenic founder variant of GCDH (c.1262C>T). We collected demographics, medical comorbidities, muscle tone patterns, Gross Motor Function Classification System level, gastrostomy tube status, seizure history, inpatient events, orthopaedic diagnoses and operative characteristics.

RESULTS

Over an average follow-up of 4.7 ± 3.4 years, 24 (21%) of 114 patients had musculoskeletal problems requiring orthopaedic consultation. Scoliosis (n = 14), hip dislocation (n = 8/15 hips), hip subluxation (n = 2/three hips), and windswept hip deformity (n = 2) in the spine and hip joint were most common. In total, 35 orthopaedic surgeries were performed in 17 (71%) patients. The most common primary operations were one-stage procedures with proximal femoral varus derotation osteotomy and/or pelvic osteotomy (n = 8/14 hips) for subluxation or dislocation. In all, 11 patients had posterior spinal fusion for severe scoliosis. With the recommended metabolic management, there were no disease-specific complications in this cohort.

CONCLUSIONS

Children with GA1 who have static striatal lesions are at risk for musculoskeletal complications, especially scoliosis and hip dislocation, and appropriate operative management requires consultation with a metabolic specialist with specific considerations for fluid management and nutrition.

LEVEL OF EVIDENCE

IV.

Intrathecal Baclofen for Hypertonia Secondary to Glutaric Aciduria Type I

Glutaric aciduria type I (GA1) is a rare organic aciduria characterized by basal ganglia dysfunction and severe dystonia and spasticity for which enteral baclofen is currently first-line therapy. Intrathecal baclofen (ITB) is a promising alternative, given the dose titratability and concentrated delivery of medication to therapeutic targets within the central nervous system. However, the response to ITB in patients with this rare condition has not been previously reported. We present a 15-year-old girl with GA1 and associated hypertonia refractory to extensive, multimodal adjuvant medical therapy including enteral baclofen. An ITB pump was implanted, and after an appropriate baclofen titration, her hypertonia and enteral pharmacologic regimen were both reduced. We demonstrate that ITB is a viable modality for treating refractory dystonia and spasticity secondary to GA1; it can objectively reduce hypertonia, subjectively improve quality of life, and minimize the side effect profile of otherwise extensive pharmacologic therapies.

Adult-onset glutaric aciduria type I: rare presentation of a treatable disorder

Glutaric aciduria type I (GA1; OMIM #231670) is an autosomal recessively inherited and treatable disorder characterized by the accumulation and irregular excretion of glutaric acid due to a defect in the glutaryl-CoA dehydrogenase enzyme involved in the catabolic pathways of L-lysine, L-hydroxylysine, and L-tryptophan. Glutaryl-CoA dehydrogenase is encoded by the GCDH gene (OMIM #608801), and several mutations in this gene are known to result in GA1. GA1 usually presents in the first 18-36 months of life with mild or severe acute encephalopathy, movement disorders, and striatal degeneration. Few cases of adult-onset GA1 have been described so far in the literature, often with non-specific and sometimes longstanding neurological symptoms. Since a preventive metabolic treatment is available, neurologists must be aware of this rare but likely underdiagnosed presentation, especially when typical neuroimaging features are identified. Here, we describe 35-year-old presenting with headache and subjective memory problems. There was no history of dystonic movement disorders. Neurological examination and neurocognitive tests were normal. Brain MRI scan revealed white matter abnormalities associated with subependymal nodules and mild frontotemporal hypoplasia suggestive of glutaric aciduria type 1 (GA1). Genetic testing confirmed the presence of homozygous c.1204C > T (p.R402W) variant in the GCDH gene, inherited from heterozygous parents.

Is Expanded Newborn Screening Adequate to Detect Indian Biochemical Low Excretor Phenotype Patients of Glutaric Aciduria Type I?

OBJECTIVE

To investigate if expanded newborn screening using tandem mass spectroscopy (TMS) is adequate to detect low excretor phenotype in Indian Glutaric aciduria type I (GA-I) patients.

METHODS

Ten GA-I patients were investigated for blood glutaryl carnitine (C5DC) levels on dried blood spot (DBS) by tandem mass spectroscopy and urine glutaric acid (GA) and 3-hydroxyglutaric acid (3-OH-GA) by gas chromatography-mass spectroscopy. The student's T test and Pearson's correlation were applied to draw a relationship between various biochemical parameters. Further confirmation of low excretors by DNA mutation analysis in the glutaryl CoA dehydrogenase (GCDH) gene was performed by polymerase chain reaction and Sangers sequencing.

RESULTS

Among 10 GA-I patients, 7 patients were found to have high excretor, and 3 were found to have low excretor phenotype. The low excretors were found to have GCDH gene mutations. The mean C5DC levels in high and low excretors were 2.61 ± 2.02 μmol/L and 2.31 ± 1.00 μmol/L, respectively. In high excretors, C5DC levels correlated with GA (r = 0.95). In low excretors, C5DC levels correlated with 3-OH-GA (r = 0.99). No significant difference was found between C5DC levels of high and low excretors (p = 0.82).

CONCLUSIONS

The MS/MS, C5DC screening is a sensitive technique and detected 10 GA-I patients. Irrespective of the urine organic acid levels, Indian GA-I patients including low excretors seem to have a significantly elevated C5DC level and well above the stipulated cut-off values and therefore, expanded newborn screening is probably adequate to diagnose them.

What are the information needs of parents caring for a child with Glutaric aciduria type 1?

Background

Newborn screening has enabled the early diagnosis of Glutaric aciduria type 1, with the possibility of improving neurological outcomes in affected children. Achieving those outcomes requires parents to effectively manage their child’s condition by adherence to a strict dietary regime and responding to situations that may trigger decompensation. The specific information and support needs of this group of parents are unknown.

Methods

A focus group with five parents was conducted to gain insights into the information that parents needed and the ways in which they accessed and used information to manage their child’s condition. A topic guide was used to direct the discussion which was recorded and fully transcribed. All participants gave informed consent. Data were analysed using thematic analysis, a structured approach that contributes to transparency and validity of results while allowing the integration of predetermined and emerging themes. To ensure rigour, two researchers were involved in initial coding of data and key analytic decisions.

Results

Two main themes were identified. ‘Understanding the condition’ explored parent’s needs to understand the scientific complexity of the condition and to be aware of the worst case scenario associated with loss of metabolic control. ‘Managing the condition’ explained how parents co-ordinated and controlled the involvement of other carers and parents’ need to be active partners in medical management to feel in control of the situation.

Conclusions

The study highlights the importance of addressing parents’ initial and ongoing informational needs so they can fulfil their role and protect their child from metabolic harm.

Clinical, biochemical, neuroradiological and molecular characterization of Egyptian patients with glutaric acidemia type 1

Glutaric acidemia type 1 (GA1) is an inherited metabolic autosomal recessive disorder that is caused by a deficiency in glutaryl-CoA dehydrogenase (GCDH). Untreated patients suffer primarily from severe striatal damage. More than 250 variants in the GCDH gene have been reported with a variable frequency among different ethnic groups. In this study, we aimed to characterize 89 Egyptian patients with GA1 and identify the variants in the 41 patients who were available for genotyping. All of our patients demonstrated clinical, neuroradiological, and biochemical characteristics that are consistent with a diagnosis of GA1. All patients presented with variable degrees of developmental delay ranging from mild to severe. Most of the 89 patients presented with acute onset type (71.9%), followed by insidious (19%) and asymptomatic (9%). A delay in diagnosis was inversely associated with macrocephaly. The prevalence rate ratio (PR) for macrocephaly that was associated with each 6-month delay was 0.95 (95%CI 0.91-0.99). However, high body weight was associated with a higher likelihood of having macrocephaly (PR 1.16, 95%CI 1.06-1.26 per 1 SD increment of Z score weight). However, body weight was inversely associated with the morbidity score. Consanguinity level was 64% among our patient's cohort and was positively associated with the C5DC level (β (95%CI) 1.06 (0.12-1.99)). Forty-one patients were available for genotyping and were sequenced for the GCDH gene. We identified a total of 25 variants, of which the following six novel variants were identified: three missense variants, c.320G > T (p.Gly107Val), c.481C > T (p.Arg161Trp) and c.572 T > G (p.Met191Arg); two deletions, c.78delG (p.Ala27Argfs34) and c.1035delG (p.Gly346Alafs*11); and one indel, c.272_331del (p.Val91_Lys111delinsGlu). All of the novel variants were absent in the 300 normal chromosomes. The most common variant, c.*165A > G, was detected in 42 alleles, and the most commonly detected missense variant, c.1204C > T (p.Arg402Trp), was identified in 29 mutated alleles in 15/41 (34.2%) of patients. Our findings suggest that GA1 is not uncommon organic acidemia disease in Egypt; therefore, there is a need for supporting neonatal screening programs in Egypt.

l-Carnitine prevents oxidative stress in striatum of glutaryl-CoA dehydrogenase deficient mice submitted to lysine overload

The deficiency of the enzyme glutaryl-CoA dehydrogenase leads to predominant accumulation of glutaric acid (GA) in the organism and is known as glutaric acidemia type I (GA1). Despite the mechanisms of brain damage involved in GA1 are not fully understood, oxidative stress may be involved in this process. Treatment is based on protein/lysine (Lys) restriction and l-carnitine (L-car) supplementation. L-car was recently shown to have an important antioxidant role. A knockout mice model (Gcdh^-/-) submitted to a dietary overload of Lys was developed to better understand the GA1 pathogenesis. In this study, we evaluated L-car and glutarylcarnitine levels, the lipid and protein damage, reactive oxygen species (ROS) production and antioxidant enzymes activities in striatum of Gcdh^-/- and wild-type (WT) mice. We also determined the effect of the L-car treatment on these parameters. Thirty-day-old Gcdh^-/- and WT mice were fed a normal chow (0.9% Lys) or submitted to a high Lys diet (4.7%) for 72 h. Additionally, these animals were administered with three intraperitoneal injections of saline or L-car in different times. Gcdh^-/- mice were deficient in L-car and presented a higher glutarylcarnitine levels. They also presented lipid and protein damage, an increased ROS production and altered antioxidant enzymes compared to WT mice. Additionally, mice exposed to Lys overload presented higher alterations in these parameters than mice under normal diet, which were significantly decreased or normalized in those receiving L-car. Thus, we demonstrated a new beneficial effect of the L-car treatment attenuating or abolishing the oxidative stress process in Gcdh^-/- mice.

Ammonium accumulation and chemokine decrease in culture media of Gcdh-/- 3D reaggregated brain cell cultures

Glutaric Aciduria type I (GA-I) is caused by mutations in the GCDH gene. Its deficiency results in accumulation of the key metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body tissues and fluids. Present knowledge on the neuropathogenesis of GA-I suggests that GA and 3-OHGA have toxic properties on the developing brain. We analyzed morphological and biochemical features of 3D brain cell aggregates issued from Gcdh^-/- mice at two different developmental stages, day-in-vitro (DIV) 8 and 14, corresponding to the neonatal period and early childhood. We also induced a metabolic stress by exposing the aggregates to 10 mM l-lysine (Lys). Significant amounts of GA and 3-OHGA were detected in Gcdh^-/- aggregates and their culture media. Ammonium was significantly increased in culture media of Gcdh^-/- aggregates at the early developmental stage. Concentrations of GA, 3-OHGA and ammonium increased significantly after exposure to Lys. Gcdh^-/- aggregates manifested morphological alterations of all brain cell types at DIV 8 while at DIV 14 they were only visible after exposure to Lys. Several chemokine levels were significantly decreased in culture media of Gcdh^-/- aggregates at DIV 14 and after exposure to Lys at DIV 8. This new in vitro model for brain damage in GA-I mimics well in vivo conditions. As seen previously in WT aggregates exposed to 3-OHGA, we confirmed a significant ammonium production by immature Gcdh^-/- brain cells. We described for the first time a decrease of chemokines in Gcdh^-/- culture media which might contribute to brain cell injury in GA-I.

Anandamide Reduces the Toxic Synergism Exerted by Quinolinic Acid and Glutaric Acid in Rat Brain Neuronal Cells

The endocannabinoid system (ECS) regulates several physiological processes in the Central Nervous System, including the modulation of neuronal excitability via activation of cannabinoid receptors (CBr). Both glutaric acid (GA) and quinolinic acid (QUIN) are endogenous metabolites that, under pathological conditions, recruit common toxic mechanisms. A synergistic effect between them has already been demonstrated, supporting potential implications for glutaric acidemia type I (GA I). Here we investigated the possible involvement of a cannabinoid component in the toxic model exerted by QUIN + GA in rat cortical slices and primary neuronal cell cultures. The effects of the CB1 receptor agonist anandamide (AEA), and the fatty acid amide hydrolase inhibitor URB597, were tested on cell viability in cortical brain slices and primary neuronal cultures exposed to QUIN, GA, or QUIN + GA. As a pre-treatment to the QUIN + GA condition, AEA prevented the loss of cell viability in both preparations. URB597 only protected in a moderate manner the cultured neuronal cells against the QUIN + GA-induced damage. The use of the CB1 receptor reverse agonist AM251 in both biological preparations prevented partially the protective effects exerted by AEA, thus suggesting a partial role of CB1 receptors in this toxic model. AEA also prevented the cell damage and apoptotic death induced by the synergic model in cell cultures. Altogether, these findings demonstrate a modulatory role of the ECS on the synergic toxic actions exerted by QUIN + GA, thus providing key information for the understanding of the pathophysiological events occurring in GA I.

Patterns, evolution, and severity of striatal injury in insidious- vs acute-onset glutaric aciduria type 1

BACKGROUND

Striatal injury in patients with glutaric aciduria type 1 (GA1) results in a complex, predominantly dystonic, movement disorder. Onset may be acute following acute encephalopathic crisis (AEC) or insidious without apparent acute event.

METHODS

We analyzed clinical and striatal magnetic resonance imaging (MRI) findings in 21 symptomatic GA1 patients to investigate if insidious- and acute-onset patients differed in timing, pattern of striatal injury, and outcome.

RESULTS

Eleven patients had acute and ten had insidious onset, two with later AEC (acute-on-insidious). The median onset of dystonia was 10 months in both groups, and severity was greater in patients after AEC (n = 8 severe, n = 5 moderate) than in insidious onset (n = 4 mild, n = 3 moderate, n = 1 severe). Deviations from guideline-recommended basic metabolic treatment were identified in six insidious-onset patients. Striatal lesions were extensive in all acute-onset patients and restricted to the dorsolateral putamen in eight of ten insidious-onset patients. After AEC, the two acute-on-insidious patients had extensive striatal changes superimposed on pre-existing dorsolateral putaminal lesions. Two insidious-onset patients with progressive dystonia without overt AEC also had extensive striatal changes, one with sequential striatal injury revealed by diffusion-weighted imaging. Insidious-onset patients had a latency phase of 3.5 months to 6.5 years between detection and clinical manifestation of dorsolateral putaminal lesions.

CONCLUSIONS

Insidious-onset type GA1 is characterized by dorsolateral putaminal lesions, less severe dystonia, and an asymptomatic latency phase, despite already existing lesions. Initially normal MRI during the first months and deviations from guideline-recommended treatment in a large proportion of insidious-onset patients substantiate the protective effect of neonatally initiated treatment.

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.

Oxidative damage in glutaric aciduria type I patients and the protective effects of l-carnitine treatment

The deficiency of the enzyme glutaryl-CoA dehydrogenase, known as glutaric acidemia type I (GA-I), leads to the accumulation of glutaric acid (GA) and glutarilcarnitine (C5DC) in the tissues and body fluids, unleashing important neurotoxic effects. l-carnitine (l-car) is recommended for the treatment of GA-I, aiming to induce the excretion of toxic metabolites. l-car has also demonstrated an important role as antioxidant and anti-inflammatory in some neurometabolic diseases. This study evaluated GA-I patients at diagnosis moment and treated the oxidative damage to lipids, proteins, and the inflammatory profile, as well as in vivo and in vitro DNA damage, reactive nitrogen species (RNS), and antioxidant capacity, verifying if the actual treatment with l-car (100 mg kg^-1  day^-1 ) is able to protect the organism against these processes. Significant increases of GA and C5DC were observed in GA-I patients. A deficiency of carnitine in patients before the supplementation was found. GA-I patients presented significantly increased levels of isoprostanes, di-tyrosine, urinary oxidized guanine species, and the RNS, as well as a reduced antioxidant capacity. The l-car supplementation induced beneficial effects reducing these biomarkers levels and increasing the antioxidant capacity. GA, in three different concentrations, significantly induced DNA damage in vitro, and the l-car was able to prevent this damage. Significant increases of pro-inflammatory cytokines IL-6, IL-8, GM-CSF, and TNF-α were shown in patients. Thus, the beneficial effects of l-car presented in the treatment of GA-I are due not only by increasing the excretion of accumulated toxic metabolites, but also by preventing oxidative damage.

Patterns, evolution, and severity of striatal injury in insidious- versus acute-onset glutaric aciduria type 1

BACKGROUND

Striatal injury in patients with glutaric aciduria type 1 (GA1) results in a complex, predominantly dystonic, movement disorder. Onset may be acute following acute encephalopathic crisis (AEC) or insidious without apparent acute event.

METHODS

We analyzed clinical and striatal magnetic resonance imaging (MRI) findings in 21 symptomatic GA1 patients to investigate if insidious- and acute-onset patients differed in timing, pattern of striatal injury, and outcome.

RESULTS

Eleven patients had acute and ten had insidious onset, two with later AEC (acute-on-insidious). The median onset of dystonia was 10 months in both groups, and severity was greater in patients after AEC (n = 8 severe, n = 5 moderate) than in insidious onset (n = 4 mild, n = 3 moderate, n = 1 severe). Deviations from guideline-recommended basic metabolic treatment were identified in six insidious-onset patients. Striatal lesions were extensive in all acute-onset patients and restricted to the dorsolateral putamen in eight of ten insidious-onset patients. After AEC, the two acute-on-insidious patients had extensive striatal changes superimposed on pre-existing dorsolateral putaminal lesions. Two insidious-onset patients with progressive dystonia without overt AEC also had extensive striatal changes, one with sequential striatal injury revealed by diffusion-weighted imaging. Insidious-onset patients had a latency phase of 3.5 months to 6.5 years between detection and clinical manifestation of dorsolateral putaminal lesions.

CONCLUSIONS

Insidious-onset type GA1 is characterized by dorsolateral putaminal lesions, less severe dystonia, and an asymptomatic latency phase, despite already existing lesions. Initially normal MRI during the first months and deviations from guideline-recommended treatment in a large proportion of insidious-onset patients substantiate the protective effect of neonatally initiated treatment.

Favourable outcome in a child with symptomatic diagnosis of Glutaric aciduria type 1 despite vertical HIV infection and minor head trauma

The first case of Glutaric aciduria Type 1(GA1) in an African child was reported in 2001. GA1 has a prevalence of 1:5000 in black South Africans. Although early diagnosis is essential for a favourable outcome, newborn screening is not routine in South Africa where an estimated 320,000 children have HIV infection. Neurodevelopmental delay and encephalopathy are complications of both HIV and GA1. In such a setting it is important to recognise that HIV and GA1 can occur simultaneously. We present an HIV-infected South African male child of Xhosa descent with macrocephaly who commenced combination antiretroviral therapy (ART) at 8 weeks of age in a clinical trial which included a neurodevelopmental sub-study. He developed short-lived focal seizures at 16 months after minor head trauma. Neurological examination was normal. Neuroimaging showed temporal lobe atrophy, subtle hyperintense signal change in the globus pallidus, and focal haemosiderosis in the right Sylvian fissure region. As findings were not in keeping with HIV encephalopathy, a urine metabolic screen was undertaken which suggested GA1. Genetic testing confirmed Arg293Trp mutation. He began L-carnitine and a low protein diet as a restricted diet was not practicable. At 21 months he developed pulmonary tuberculosis, requiring 6 months treatment. He did not develop any neurologic motor symptoms. Serial neurodevelopmental and neuropsychological test scores until 9 years were similar to healthy neighbourhood controls, except for mild language delay at 3½ years. Detection of GA1, probably facilitated through participation in a clinical trial, was pivotal for a favourable outcome. The concomitant use of ART and anti-tuberculous therapy in a child with GA1 appears safe.

Glutaric Aciduria Type 1 with Microcephaly: Masquerading as Spastic Cerebral Palsy

Glutaric aciduria type 1 (GA-1) is an autosomal-recessive disorder caused by the deficiency of the mitochondrial enzyme glutaryl-CoA dehydrogenase. A 13-month-old boy presented with microcephaly, developmental delay, and progressive spasticity and was being treated as spastic cerebral palsy, later on had loss of developmental milestones after acute episode of illness at 12 months of age. The magnetic resonance imaging of brain revealed widened Sylvian fissure, hyperintensities in bilateral globus pallidus, and bilateral frontoparietal atrophy along with white matter loss. The urine examination by gas chromatography–mass spectroscopy revealed a marked excretion of glutaric acid and 3-hydroxyglutaric acid. The diagnosis of GA-1 was confirmed on the basis of characteristic neuroimaging, biochemical, and mutation studies. There are rare reports in the literature about association of GA-1 with microcephaly. The child was started on trihexyphenidyl, l -carnitine, and high-dose riboflavin, and dietary therapy in the form of low-protein diet was advised.

Impairment of astrocytic glutaminolysis in glutaric aciduria type I

Glutaric aciduria type I is a rare, autosomal recessive, inherited defect of glutaryl-CoA dehydrogenase. Deficiency of this protein in L-lysine degradation leads to the characteristic accumulation of nontoxic glutarylcarnitine and neurotoxic glutaric acid (GA), glutaryl-CoA, and 3-hydroxyglutaric acid. Untreated patients develop bilateral lesions of basal ganglia resulting in a complex movement disorder with predominant dystonia in infancy and early childhood. The current pathomechanistic concept strongly focuses on imbalanced neuronal energy metabolism due to accumulating metabolites, whereas little is known about the pathomechanistic role of astrocytes, which are thought to be in constant metabolic crosstalk with neurons. We found that glutaric acid (GA) causes astrocytic cell death under starvation cell culture conditions, i.e. low glucose, without glutamine and fetal calf serum. Glutamine completely abolished GA-induced toxicity, suggesting involvement of glutaminolysis. Increasing dependence on glutaminolysis by chemical induction of hypoxia signaling-potentiated GA-induced toxicity. We further show that GA disturbs glutamine degradation by specifically inhibiting glutamate dehydrogenase. Summarizing our study shows that pathologically relevant concentrations of GA block an important step in the metabolic crosstalk between neurons and astrocytes, ultimately leading to astrocytic cell death.