Glutaric aciduria type I: outcome of patients with early- versus late-diagnosis

Evaluation of the first 5 years of a glutaric aciduria type I neonatal screening programme in Asturias

INTRODUCTION

. Neonatal screening of glutaric aciduria type 1 (GA-1) has brought radical changes in the course and outcomes of this disease. This study analyses the outcomes of the first 5 years (2015-2019) of the AGA1 neonatal screening programme in our autonomous community.

MATERIAL

. We conducted an observational, descriptive and retrospective study. All neonates born between January 1, 2015 and December 31, 2019 that participated in the neonatal screening programme were included in the study. The glutarylcarnitine (C5DC) concentration in dry blood spot samples was measured by means of tandem mass spectrometry applying a cut-off point of 0.25 µmol/L.

RESULTS

. A total of 30 120 newborns underwent screening. We found differences in the C5DC concentration based on gestational age, type of feeding and hours of life at sample collection. These differences were not relevant for screening purposes. There were no differences between neonates with weights smaller and greater than 1500 g. Screening identified 2 affected patients and there were 3 false positives. There were no false negatives. The diagnosis was confirmed by genetic testing. Patients have been in treatment since diagnosis and have not developed encephalopathic crises in the first 4 years of life.

CONCLUSIONS

. Screening allowed early diagnosis of two cases of GA-1 in the first 5 years since its introduction in our autonomous community. Although there were differences in C5DC levels based on gestational age, type of feeding and hours of life at blood extraction, they were not relevant for screening.

Modeling Glutaric Aciduria Type I in human neuroblastoma cells recapitulates neuronal damage that can be rescued by gene replacement

Glutaric Aciduria type I (GA1) is a rare neurometabolic disorder caused by mutations in the GDCH gene encoding for glutaryl-CoA dehydrogenase (GCDH) in the catabolic pathway of lysine, hydroxylysine and tryptophan. GCDH deficiency leads to increased concentrations of glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body fluids and tissues. These metabolites are the main triggers of brain damage. Mechanistic studies supporting neurotoxicity in mouse models have been conducted. However, the different vulnerability to some stressors between mouse and human brain cells reveals the need to have a reliable human neuronal model to study GA1 pathogenesis. In the present work we generated a GCDH knockout (KO) in the human neuroblastoma cell line SH-SY5Y by CRISPR/Cas9 technology. SH-SY5Y-GCDH KO cells accumulate GA, 3-OHGA, and glutarylcarnitine when exposed to lysine overload. GA or lysine treatment triggered neuronal damage in GCDH deficient cells. SH-SY5Y-GCDH KO cells also displayed features of GA1 pathogenesis such as increased oxidative stress vulnerability. Restoration of the GCDH activity by gene replacement rescued neuronal alterations. Thus, our findings provide a human neuronal cellular model of GA1 to study this disease and show the potential of gene therapy to rescue GCDH deficiency.

Update current understanding of neurometabolic disorders related to lysine metabolism

Lysine, as an essential amino acid, predominantly undergoes metabolic processes through the saccharopine pathway, whereas a smaller fraction follows the pipecolic acid pathway. Although the liver is considered the primary organ for lysine metabolism, it is worth noting that lysine catabolism also takes place in other tissues and organs throughout the body, including the brain. Enzyme deficiency caused by pathogenic variants in its metabolic pathway may lead to a series of neurometabolic diseases, among which glutaric aciduria type 1 and pyridoxine-dependent epilepsy have the most significant clinical manifestations. At present, through research, we have a deeper understanding of the multiple pathophysiological mechanisms related to these diseases, including intracerebral accumulation of neurotoxic metabolites, imbalance between GABAergic and glutamatergic neurotransmission, energy deprivation due to metabolites, and the dysfunction of antiquitin. Because of the complexity of these diseases, their clinical manifestations are also diverse. The early implementation of lysine-restricted diets and supplementation with arginine and carnitine has reported positive impacts on the neurodevelopmental outcomes of patients. Presently, there is more robust evidence supporting the effectiveness of these treatments in glutaric aciduria type 1 compared with pyridoxine-dependent epilepsy.

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.

2-Methylglutaconic acid as a biomarker in routine urine organic acids leading to the diagnosis of glutaric acidemia type I in a low excretor

GA1 (OMIM# 231670) is an organic aciduria caused by defective Glutaryl-CoA dehydrogenase (GCDH), encoded by GCDH. Early detection of GA1 is crucial to prevent patients from developing acute encephalopathic crisis and subsequent neurologic sequelae. Diagnosis of GA1 relies on elevated glutarylcarnitine (C5DC) in plasma acylcarnitine analysis and hyperexcretion of glutaric acid (GA) and 3-hydroxyglutaric acid (3HG) in urine organic acid (UOA) analysis. Low excretors (LE), however, exhibit subtly elevated or even normal plasma C5DC and urinary GA levels, leading to screening and diagnostic challenges. The measurement of 3HG in UOA is thus often used as the 1st tier test for GA1. We described a case of LE detected via newborn screen with normal excretion of GA, absent of 3HG and increased 2-methylglutaconic acid (2MGA), which was detected at 3 mg/g creatinine (reference interval <1 mg/g creatinine) without appreciable ketones. We retrospectively examined UOA of 8 other GA1 patients and the 2MGA level ranged from 2.5 to 27.39 mg/g creatinine, which is significantly higher than normal controls (0.05-1.61 mg/g creatinine). Although the underlying mechanism of 2MGA formation in GA1 is unclear, our study suggests 2MGA is a biomarker for GA1 and should be monitored by routine UOA to evaluate its diagnostic and prognostic value.

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.

Identification of novel pathogenic variants in the GCDH gene and assessment of neurodevelopmental outcomes in 24 children with glutaric aciduria type 1

AIM

To evaluate the pathogenic variants in GCDH gene and to assess the neurodevelopmental outcomes in children with Glutaric aciduria type 1 (GA-1).

METHOD

Cross-sectional observational study between January 2019 and June 2020 in consecutive North Indian children with a clinical and biochemical suspicion of GA-1. Variants in the coding regions of GCDH gene were identified through Sanger sequencing. Neurodevelopmental and quality of life assessment was done using standardized scales.

RESULTS

24 children with GA-1 were identified. The median age at diagnosis was 12 months and the median delay in diagnosis was 3 months. Genetic analysis was done in 14 cases. It revealed 12 variants (11 missense and one nonsense) from 13 patients. Most of the pathogenic variants were in exon 9 and exon 5. Three novel variants were identified in three patients: two missense variants c.169G > A (p.Glu57Lys), c.1048T > C (p.Cys350Arg) and one nonsense variant c.331C > T (p.Lys111Ter). On neurodevelopmental assessment, majority of children with GA-1 were non ambulatory (62.5%), had limited hand skills (58.3%) and impaired communication (58.3%). Overall, poor global development was noted in 43.7%. A pre-existing developmental delay was significantly associated with impaired communication skills (p = 0.03), and the number of episodes of encephalopathy were significantly associated with impaired gross motor skill (p = 0.02). Presence of encephalopathy was significantly associated with poor performance in social emotional (p = 0.01) and cognitive (p = 0.03) domains of Developmental Profile-III scale and development of severe dystonia (p = 0.01).

CONCLUSION

Our findings highlight the clinical, biochemical, radiological and genetic spectrum of GA-1 in children in North India and report the presence of novel pathogenic variations.

Diagnosis of inborn errors of metabolism within the expanded newborn screening in the Madrid region

We present the results of our experience in the diagnosis of inborn errors of metabolism (IEM) since the Expanded Newborn Screening was implemented in our Region. Dried blood samples were collected 48 h after birth. Amino acids and acylcarnitines were quantitated by mass spectrometry (MS)/MS. Newborns with alterations were referred to the clinical centers for follow-up. Biochemical and molecular genetic studies for confirmation of a disease were performed. In the period 2011 to 2019, 592 822 children were screened: 902 of them were referred for abnormal results. An IEM was confirmed in 222 (1/2670): aminoacidopathies: 89 hyperphenylalaninemia (HPA) (51 benign HPA, 32 phenylketonuria, 4 DNAJC12 defect, and 2 primapterinuria), 6 hypermethioninemia, 3 tyrosinemia type 1 (TYR-1), 1 TYR-3, 4 maple syrup urine disease (MSUD), 2 branched-chain amino acid transferase 2 deficiency, 2 homocystinuria, 1 cystinuria, 2 ornithine transcarbamylase (OTC) deficiency, 2 citrullinemia type I (CTLN1); FAO defects: 43 medium-chain acyl-CoA dehydrogenase deficiency (MCADD), 13 very long-chain acyl-CoA dehydrogenase deficiency, 2 long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD), 1 multiple acyl-coA dehydrogenation deficiency, 11 systemic primary carnitine deficiency, 2 carnitine palmitoyltransferase type 2 (CPT-II) deficiency, 1 CPT-I deficiency; organic acidurias: 12 glutaric aciduria type 1 (GA-1), 4 methylmalonic acidemia (MMA), 7 MMA including combined cases with homocystinuria (MMAHC), 6 propionic acidemia (PA), 7 3-methylcrotonyl-CoA carboxylase, 1 3-hydroxy-3-methylglutaryl-CoA lyase deficiency lyase deficiency. Only 19 infants (8.5%) were symptomatic at newborn screening result (1 LCHADD, 5 PA, 1 CPT-II deficiency, 1 MMA, 3 MMAHC, 2 MSUD, 2 OTC deficiency, 1 CTLN1, 1 MCADD, 2 TYR-1). No false negative cases were identified. Genetic diagnosis was conclusive in all biochemically confirmed cases, except for two infants with HPA, identifying pathogenic variants in 32 different genes. The conditions with the highest incidence were HPA (1/6661) and MCAD deficiencies (1/13 787).

A knock-in rat model unravels acute and chronic renal toxicity in glutaric aciduria type I

Glutaric aciduria type I (GA-I, OMIM # 231670) is an autosomal recessive inborn error of metabolism caused by deficiency of the mitochondrial enzyme glutaryl-CoA dehydrogenase (GCDH). The principal clinical manifestation in GA-I patients is striatal injury most often triggered by catabolic stress. Early diagnosis by newborn screening programs improved survival and reduced striatal damage in GA-I patients. However, the clinical phenotype is still evolving in the aging patient population. Evaluation of long-term outcome in GA-I patients recently identified glomerular filtration rate (GFR) decline with increasing age. We recently created the first knock-in rat model for GA-I harboring the mutation p.R411W (c.1231 C>T), corresponding to the most frequent GCDH human mutation p.R402W. In this study, we evaluated the effect of an acute metabolic stress in form of high lysine diet (HLD) on young Gcdh^ki/ki rats. We further studied the chronic effect of GCDH deficiency on kidney function in a longitudinal study on a cohort of Gcdh^ki/ki rats by repetitive ⁶⁸Ga-EDTA positron emission tomography (PET) renography, biochemical and histological analyses. In young Gcdh^ki/ki rats exposed to HLD, we observed a GFR decline and biochemical signs of a tubulopathy. Histological analyses revealed lipophilic vacuoles, thinning of apical brush border membranes and increased numbers of mitochondria in proximal tubular (PT) cells. HLD also altered OXPHOS activities and proteome in kidneys of Gcdh^ki/ki rats. In the longitudinal cohort, we showed a progressive GFR decline in Gcdh^ki/ki rats starting at young adult age and a decline of renal clearance. Histopathological analyses in aged Gcdh^ki/ki rats revealed tubular dilatation, protein accumulation in PT cells and mononuclear infiltrations. These observations confirm that GA-I leads to acute and chronic renal damage. This raises questions on indication for follow-up on kidney function in GA-I patients and possible therapeutic interventions to avoid renal damage.

Clinical, Biochemical, and Genetic Heterogeneity in Glutaric Aciduria Type II Patients

The variants of electron transfer flavoprotein (ETFA, ETFB) and ETF dehydrogenase (ETFDH) are the leading cause of glutaric aciduria type II (GA-II). In this study, we identified 13 patients harboring six variants of two genes associated with GA-II. Out of the six variants, four were missense, and two were frameshift mutations. A missense variant (ETFDH:p.Gln269His) was observed in a homozygous state in nine patients. Among nine patients, three had experienced metabolic crises with recurrent vomiting, abdominal pain, and nausea. In one patient with persistent metabolic acidosis, hypoglycemia, and a high anion gap, the ETFDH:p.Gly472Arg, and ETFB:p.Pro94Thrfs*8 variants were identified in a homozygous, and heterozygous state, respectively. A missense variant ETFDH:p.Ser442Leu was detected in a homozygous state in one patient with metabolic acidosis, hypoglycemia, hyperammonemia and liver dysfunction. The ETFDH:p.Arg41Leu, and ETFB:p.Ile346Phefs*19 variants were observed in a homozygous state in one patient each. Both these variants have not been reported so far. In silico approaches were used to evaluate the pathogenicity and structural changes linked with these six variants. Overall, the results indicate the importance of a newborn screening program and genetic investigations for patients with GA-II. Moreover, careful interpretation and correlation of variants of uncertain significance with clinical and biochemical findings are needed to confirm the pathogenicity of such variants.

Biochemical and molecular features of Chinese patients with glutaric acidemia type 1 detected through newborn screening

Background

Glutaric acidemia type 1 (GA1) is a treatable disorder affecting cerebral organic acid metabolism caused by a defective glutaryl-CoA dehydrogenase (GCDH) gene. GA1 diagnosis reports following newborn screening (NBS) are scarce in the Chinese population. This study aimed to assess the acylcarnitine profiles and genetic characteristics of patients with GA1 identified through NBS.

Results

From January 2014 to September 2020, 517,484 newborns were screened by tandem mass spectrometry, 102 newborns with elevated glutarylcarnitine (C5DC) levels were called back. Thirteen patients were diagnosed with GA1, including 11 neonatal GA1 and two maternal GA1 patients. The incidence of GA1 in the Quanzhou region was estimated at 1 in 47,044 newborns. The initial NBS results showed that all but one of the patients had moderate to markedly increased C5DC levels. Notably, one neonatal patient with low free carnitine (C0) level suggest primary carnitine deficiency (PCD) but was ultimately diagnosed as GA1. Nine neonatal GA1 patients underwent urinary organic acid analyses: eight had elevated GA and 3HGA levels, and one was reported to be within the normal range. Ten distinct GCDH variants were identified. Eight were previously reported, and two were newly identified. In silico prediction tools and protein modeling analyses suggested that the newly identified variants were potentially pathogenic. The most common variant was c.1244-2 A>C, which had an allelic frequency of 54.55% (12/22), followed by c.1261G>A (p.Ala421Thr) at 9.09% (2/22).

Conclusions

Neonatal GA1 patients with increased C5DC levels can be identified through NBS. Maternal GA1 patients can also be detected using NBS due to the low C0 levels in their infants. Few neonatal GA1 patients may have atypical acylcarnitine profiles that are easy to miss during NBS; therefore, multigene panel testing should be performed in newborns with low C0 levels. This study indicates that the GCDH variant spectra were heterogeneous in this southern Chinese cohort.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01964-5.

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.

Outcome of the glutaric aciduria type 1 (GA1) newborn screening program in Manitoba: 1980–2020

Glutaric aciduria type 1 (GA1) is a severe inherited neurometabolic disorder whose clinical outcome has improved after implementation of newborn screening (NBS) programs and prompt beginning of guideline-directed presymptomatic metabolic treatment. We report the outcome of our 40-year experience with the diagnosis and management of GA1 which has improved but remains suboptimal.

Glutaric Aciduria Type 1: A Case Report and Review of Literature

An 8-month-old male infant patient was referred to our institution (from elsewhere) with a history of fever, convulsions, dystonic posturing, altered sensorium, and loss of motor and mental milestones since past 1 month. Upon admission to our institution, a neuroimaging (magnetic resonance imaging of the brain) revealed frontoparietal atrophy, "bat-wing appearance," and basal ganglia changes. Carnitine and acylcarnitine profile revealed low total carnitine, very low free carnitine, and low free/acylcarnitine ratio, with normal levels of plasma amino acids. Urine gas chromatography mass spectrometry showed an elevated level of ketones (3-hydroxybutyric acid and acetoacetate) and glutaric acid with the presence of 3-hydroxyglutaric acid, suggestive of glutaric aciduria type 1. Diet modification and pharmacotherapy with riboflavin and carnitine arrested the neurological deterioration in the patient.

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.

Mild phenotype of glutaric aciduria type 1 in polish patients - novel data from a group of 13 cases

Glutaric aciduria type 1 is a neurometabolic disorder, caused by riboflavin-dependent glutaryl-CoA dehydrogenase deficiency. As its consequence, accumulation of the putatively neurotoxic metabolites (glutaric and 3-hydroxyglutaric acids) in body tissues, but especially within the brain, is observed. Estimated incidence of the disease is 1 in 110,000 newborns, The prevalence however may be higher, depending on a specific ethnic group, and result in phenotypic variation as well. In this paper we present clinical data of 13 patients of Polish nationality. They all present a mild phenotype and clinical course of glutaric aciduria type 1. Based on their clinical data, presented herein, we like to pay attention to the phenotypic and neuroimaging features important for the diagnosis of mild form of this disease. Moreover, we present novel molecular data, which may correlate with such a manifestation.

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.

Fatal pitfalls in newborn screening for mitochondrial trifunctional protein (MTP)/long-chain 3-Hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

Background

Mitochondrial trifunctional protein (MTP) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency are long-chain fatty acid oxidation disorders with particularly high morbidity and mortality. Outcome can be favorable if diagnosed in time, prompting the implementation in newborn screening programs. Sporadic cases missed by the initial screening sample have been reported. However, little is known on pitfalls during confirmatory testing resulting in fatal misconception of the diagnosis.

Results

We report a series of three patients with MTP and LCHAD deficiency, in whom diagnosis was missed by newborn screening, resulting in life-threatening metabolic decompensations within the first half year of life. Two of the patients showed elevated concentrations of primary markers C16-OH and C18:1-OH but were missed by confirmatory testing performed by the maternity clinic. A metabolic center was not consulted. Confirmatory testing consisted of analyses of acylcarnitines in blood and organic acids in urine, the finding of normal excretion of organic acids led to rejection and underestimation of the diagnosis, respectively. The third patient, a preterm infant, was not identified in the initial screening sample due to only moderate elevations of C16-OH and C18:1-OH and normal secondary markers and analyte ratios.

Conclusion

Our observations highlight limitations of newborn screening for MTP/LCHAD deficiency. They confirm that analyses of acylcarnitines in blood and organic acids in urine alone are not suitable for confirmatory testing and molecular or functional analysis is crucial in diagnosing MTP/LCHAD deficiency. Mild elevations of primary biomarkers in premature infants need to trigger confirmatory testing. Our report underscores the essential role of specialized centers in confirming or ruling out diagnoses in suspicious screening results.

Early neonatal Glutaric aciduria type I hidden by perinatal asphyxia: a case report

Background

Perinatal asphyxia (PA) occurs in about 2 to 10 per 1000 live full-term births. Although neonatal epileptic seizures are observed in up to 60% of cases, PA may mimic or subtend other conditions. Hypoxia related brain injury is particularly relevant, as it may have permanent effects on neuropsychomotor development. Antepartum obstetric conditions, may, in turn, lead to hypoxic-ischemic damage to the fetus and the newborn, often underlying PA. Herein, a case of PA that hid and triggered signs and symptoms of Glutaric Aciduria type I (GA-I), is reported.

Case presentation

R.F. was born at term after prolonged labour, by induced vaginal delivery with the Kristeller manoeuvre. He presented with severe asphyxia and asystoly. Immediate cardiopulmonary resuscitation promptly restored cardiorespiratory parameters, allowing for early extubation 30 min after. During the following hours, severe axial muscle hypotonia with an increased tone of the limb extensor muscles became evident. The absence of crying and archaic reflexes persisted and there was an onset of generalized tonic or clonic seizure. First level metabolic and inflammatory markers were within the normal range. An inherited metabolic disease was then suspected, due to the persistent clinical signs of severe neurological damage without any detectable septic parameter. GA-I was assessed and specific treatment started without any clinical improvement, although ensuring adequate growth and metabolic control. Thereafter, the baby developed a severe encephalopathy with drug resistant epileptic seizures. The progression of the neurological damage and a CVC-related sepsis led him to exitus at 2 years.

Conclusions

To the best of our knowledge, this is the first case of early post-natal onset of GA-I reported in literature to date, in the absence of expanded newborn screening (NBS) programme. As expanded NBS programmes for inborn errors of metabolism have not yet been internationally adopted, we are of the opinion that such diseases may well be hidden by misleading signs and symptoms imputable to other more frequent harmful clinical conditions. Moreover, it would be advisable that neonatologists be trained to include GA-I in the differential diagnosis of neurological damage secondary to PA.

Proposed recommendations for diagnosing and managing individuals with glutaric aciduria type I: second revision

Glutaric aciduria type I (GA-I; synonym, glutaric acidemia type I) is a rare inherited metabolic disease caused by deficiency of glutaryl-CoA dehydrogenase located in the catabolic pathways of L-lysine, L-hydroxylysine, and L-tryptophan. The enzymatic defect results in elevated concentrations of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid, and glutaryl carnitine in body tissues, which can be reliably detected by gas chromatography/mass spectrometry (organic acids) and tandem mass spectrometry (acylcarnitines). Most untreated individuals with GA-I experience acute encephalopathic crises during the first 6 years of life that are triggered by infectious diseases, febrile reaction to vaccinations, and surgery. These crises result in striatal injury and consequent dystonic movement disorder; thus, significant mortality and morbidity results. In some patients, neurologic disease may also develop without clinically apparent crises at any age. Neonatal screening for GA-I us being used in a growing number of countries worldwide and is cost effective. Metabolic treatment, consisting of low lysine diet, carnitine supplementation, and intensified emergency treatment during catabolism, is effective treatment and improves neurologic outcome in those individuals diagnosed early; treatment after symptom onset, however, is less effective. Dietary treatment is relaxed after age 6 years and should be supervised by specialized metabolic centers. The major aim of this second revision of proposed recommendations is to re-evaluate the previous recommendations (Kölker et al. J Inherit Metab Dis 30:5-22, 2007b; J Inherit Metab Dis 34:677-694, 2011) and add new research findings, relevant clinical aspects, and the perspective of affected individuals.

Clinical and laboratory analysis of late-onset glutaric aciduria type I (GA-I) in Uighur: A report of two cases

The aim of the present study was to investigate the clinical, biochemical and genetic mutation characteristics of two cases of late-onset glutaric aciduria type I (GA-I) in Uighur. The clinical data and glutaryl-CoA dehydrogenase (GCDH) genetic test results of two cases of late-onset GA-I in Uighur were collected and analyzed, and reviewed with relevant literature. One patient with late-onset GA-I primarily exhibited clinical intermittent headache, while the other patient was asymptomatic. The urinary organic acid analysis detected a large number of glutaric acid and 3-hydroxy glutaric acid, 3-hydroxy-propionic acid. One patient exhibited white matter degeneration in cranial magnetic resonance imaging (MRI) and the other patient showed no abnormality. The two patients both exhibited c. 1204C >T, p.R402W, heterozygous mutation, and c. 532G >A, p.G178R, heterozygous mutation. Besides central nervous system infectious diseases, patients with clinical headache, cranial MRI-suggested bilateral temporal lobe arachnoid cyst and abnormal signals in the basal ganglia should be highly suspected as late-onset GA-I. Early diagnosis and correct treatment are key to improve its prognosis.

Neonatal Screening for Inherited Metabolic Diseases in 2016

The scope of newborn screening (NBS) programs is continuously expanding. NBS programs are secondary prevention interventions widely recognized internationally in the "field of Public Health." These interventions are aimed at early detection of asymptomatic children affected by certain diseases, with the objective to establish a definitive diagnosis and apply the proper treatment to prevent further complications and sequelae and ensure a better quality of life. The most significant event in the history of neonatal screening was the discovery of phenylketonuria in 1934. This disease has been the paradigm of inherited metabolic diseases. The next paradigm was the introduction of tandem mass spectrometry in the NBS programs that make possible the simultaneous measurement of several metabolites and consequently, the detection of several diseases in one blood spot and in an unique analysis. We aim to review the current situation of neonatal screening in 2016 worldwide and show scientific evidence of the benefits for some diseases. We will also discuss future challenges. It should be taken into account that any consideration to expand an NBS panel should involve a rigorous process of decision-making that balances benefits against the risks of harm.

Recurrent rhabdomyolysis and glutaric aciduria type I: a case report and literature review

BACKGROUND

Glutaric acidemia type I (GA-I) is a rare metabolic disorder caused by mutation of the glutaryl- CoA dehydrogenase (GCDH) gene. The occurrence of rhabdomyolysis with GA-I is extremely rare.

METHODS

We reported a child with recurrent rhabdomyolysis and undiagnosed glutaric acidemia type I (GA-I). And a literature review was performed.

RESULTS

A 4.5-year-old girl was admitted to our hospital due to recurrent rhabdomyolysis for 3 times within three years. At the third admission, she was diagnosed with GA-I by biochemical testing and mutation analysis. The girl was found to have a serine to leucine replacement mutation of the GCDH gene in exon 8 at position 764. Other three patients with rhabdomyolysis and GA-I were discovered by literature searching.

CONCLUSIONS

This report highlights that patients with GA-I may have an increased risk of rhabdomyolysis.

Metabolic, endocrine, and other genetic disorders

Metabolic, endocrine, and genetic diseases of the brain include a very large array of disorders caused by a wide range of underlying abnormalities and involving a variety of brain structures. Often these disorders manifest as recognizable, though sometimes overlapping, patterns on neuroimaging studies that may enable a diagnosis based on imaging or may alternatively provide enough clues to direct further diagnostic evaluation. The diagnostic workup can include various biochemical laboratory or genetic studies. In this chapter, after a brief review of normal white-matter development, we will describe a variety of leukodystrophies resulting from metabolic disorders involving the brain, including mitochondrial and respiratory chain diseases. We will then describe various acidurias, urea cycle disorders, disorders related to copper and iron metabolism, and disorders of ganglioside and mucopolysaccharide metabolism. Lastly, various other hypomyelinating and dysmyelinating leukodystrophies, including vanishing white-matter disease, megalencephalic leukoencephalopathy with subcortical cysts, and oculocerebrorenal syndrome will be presented. In the following section on endocrine disorders, we will examine various disorders of the hypothalamic-pituitary axis, including developmental, inflammatory, and neoplastic diseases. Neonatal hypoglycemia will also be briefly reviewed. In the final section, we will review a few of the common genetic phakomatoses. Throughout the text, both imaging and brief clinical features of the various disorders will be discussed.

Detection of glutaric acidemia type 1 in infants through tandem mass spectrometry

Glutaric acidemia type 1 (GA1) is a rare inherited metabolic disorder which goes underdiagnosed due to its latency period and subtle presentation. A pilot clinical study was conducted to assess the usefulness, specificity and sensitivity of the tandem mass (MS/MS) spectrometer, specifically the Abbott (AB) Sciex 3200, in the screening for GA1 using dried blood spots. A total of 17,100 specimens, comprising pediatric patients and healthy newborns, were screened from June 2012 to June 2014. A selection criterion was applied to increase the range of samples tested. 14 of the total specimens tested presumptive positive for GA1, of whom all were symptomatic. The diagnosis was confirmed in 4 of the 14 cases and they were started on treatment. 4 cases expired before confirmation. The remaining cases were empirically started on treatment. Most of the patients responded favorably to the dietary management. One important observation was that the older symptomatic children diagnosed with GA1 had poorer outcomes in terms of recovery of delayed milestones and mental deterioration, further emphasizing the need for early diagnosis of organic acidemias along with the other biochemical defects. Tandem mass spectrometry was found to be more than 93.33% sensitive and more than 99.42% specific. The screening test proved to be very simple and economical.

Multifactorial modulation of susceptibility to l-lysine in an animal model of glutaric aciduria type I

Glutaric aciduria type I is an inherited defect in L-lysine, L-hydroxylysine and L-tryptophan degradation caused by deficiency of glutaryl-CoA dehydrogenase (GCDH). The majority of untreated patients presents with accumulation of neurotoxic metabolites - glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) - and striatal injury. Gcdh(-/-) mice display elevated levels of GA and 3-OH-GA but do not spontaneously develop striatal lesions. L-lysine-enriched diets (appr. 235 mg/d) were suggested to induce a neurological phenotype similar to affected patients. In our hands 93% of mice stressed according to the published protocol remained asymptomatic. To understand the underlying mechanism, we modified their genetic background (F1 C57BL6/Jx129/SvCrl) and increased the daily oral L-lysine supply (235-433 mg). We identified three modulating factors, (1) gender, (2) genetic background, and (3) amount of L-lysine. Male mice displayed higher vulnerability and inbreeding for more than two generations as well as elevating L-lysine supply increased the diet-induced mortality rate (up to 89%). Onset of first symptoms leads to strongly reduced intake of food and, thus, L-lysine suggesting a threshold for toxic metabolite production to induce neurological disease. GA and 3-OH-GA tissue concentrations did not correlate with dietary L-lysine supply but differed between symptomatic and asymptomatic mice. Cerebral activities of glyceraldehyde 3-phosphate dehydrogenase, 2-oxoglutarate dehydrogenase complex, and aconitase were decreased. Symptomatic mice did not develop striatal lesions or intracerebral hemorrhages. We found severe spongiosis in the hippocampus of Gcdh(-/-) mice which was independent of dietary L-lysine supply. In conclusion, the L-lysine-induced pathology in Gcdh(-/-) mice depends on genetic and dietary parameters.

Neurodevelopmental profiles of children with glutaric aciduria type I diagnosed by newborn screening: a follow-up case series

Glutaric aciduria type I (GA-I) is an inherited metabolic disorder that may lead to severe motor disorder and cognitive impairment. GA-I is now included in the newborn screening programme in many countries as early detection allows for prompt treatment and effectively reduces the risk of poor developmental outcome. Information regarding the long-term neurodevelopmental outcome of children with GA-I treated early is sparse.We recruited children with a confirmed diagnosis of GA-I diagnosed via newborn screening, treated in our centre and >3 years of age (n = 6). Children were assessed at two time points using a comprehensive neuropsychological test battery. Four of these had been the subject of a previous report. All participants were male, 3-6 years at the initial assessment and 6-12 years of age at the follow-up assessment.Fine motor skills were below average in all patients. Speech, which was affected in all four patients reported previously, improved following speech therapy. IQ scores remained generally stable within the normal range. Executive functioning was average to high average in four patients. Behaviour, as assessed through parental questionnaires, was problematic in two patients. Compounding factors included child neglect, family history of autism and multiple admissions to hospital (n = 1 in each).GA-I affects fine motor skills and speech, regardless of early treatment, but not IQ scores. Patients with GA-I should be referred for assessment and appropriate early intervention. Further research is needed to correlate specific neuropsychological deficits with neuroimaging.

Clinical and mutational spectra of 23 Chinese patients with glutaric aciduria type 1

OBJECTIVE

Glutaric aciduria type 1 (GA1) is a rare neurometabolic disorder caused by glutaryl-CoA dehydrogenase deficiency due to GCDH gene mutations. In this study, the clinical presentation and molecular aspects of 23 Chinese patients (11 males and 12 females) were investigated.

METHODS

All patients were diagnosed by elevated urinary glutaric acid and GCDH gene analysis. Protein-restricted diet supplemented with special formula, l-carnitine and GABA analog were initialed after diagnosis. The clinical and biochemical features were analyzed. Mutational analysis of GCDH was conducted.

RESULTS

Clinical manifestations of 23 patients varied from asymptomatic to severe encephalopathy, with notable phenotypic differences between siblings with the same mutations. One case was detected by newborn screening, while 22 Cases were diagnosed between the ages of 5 months and 51 years. 29 mutations in GCDH were identified. Among them, 11 were novel, including seven missense mutations (c.406G > T, C.416C > G, c.442G > A, c.640A > G, c.901G > A, c.979G > A, and c.1207C > T), three frameshift mutations (c.873delC, c.1172-1173insT and c.1282-1285ins71) and one nonsense mutation (c.411C > G). In exon 5, c.553G > A and c.148T > C were found in four alleles (8.7%) and three alleles (6.5%) of the patients, respectively.

CONCLUSIONS

In 23 Chinese patients with GA1, 11 novel GCDH mutations were identified. This may indicate that the genetic profiles of Chinese patients are different from those of other populations.

SYNOPSIS

23 Chinese GA1 patients with varied clinical manifestations have been reported. 11 novel mutations in their GCDH gene were identified, indicating that the genetic profiles of Chinese GA1 patients differ from those of other populations.

Unravelling the complex MRI pattern in glutaric aciduria type I using statistical models-a cohort study in 180 patients

BACKGROUND

Glutaric aciduria type I (GA-I) is a cerebral organic aciduria caused by inherited deficiency of glutaryl-CoA dehydrogenase and is characterized biochemically by an accumulation of putatively neurotoxic dicarboxylic metabolites. The majority of untreated patients develops a complex movement disorder with predominant dystonia during age 3-36 months. Magnetic resonance imaging (MRI) studies have demonstrated striatal and extrastriatal abnormalities.

AIMS/METHODS

The major aim of this study was to elucidate the complex neuroradiological pattern of patients with GA-I and to associate the MRI findings with the severity of predominant neurological symptoms. In 180 patients, detailed information about the neurological presentation and brain region-specific MRI abnormalities were obtained via a standardized questionnaire.

RESULTS

Patients with a movement disorder had more often MRI abnormalities in putamen, caudate, cortex, ventricles and external CSF spaces than patients without or with minor neurological symptoms. Putaminal MRI changes and strongly dilated ventricles were identified as the most reliable predictors of a movement disorder. In contrast, abnormalities in globus pallidus were not clearly associated with a movement disorder. Caudate and putamen as well as cortex, ventricles and external CSF spaces clearly collocalized on a two-dimensional map demonstrating statistical similarity and suggesting the same underlying pathomechanism.

CONCLUSIONS

This study demonstrates that complex statistical methods are useful to decipher the age-dependent and region-specific MRI patterns of rare neurometabolic diseases and that these methods are helpful to elucidate the clinical relevance of specific MRI findings.

Identification of the plasma metabolomics as early diagnostic markers between biliary atresia and neonatal hepatitis syndrome

Early detection is the most effective way to improve the clinical outcome of biliary atresia (BA). Emerging metabolomics provides a powerful platform for discovering novel biomarkers and biochemical pathways to improve early diagnosis. The aim of this study is to find the potential biomarkers to distinguish BA from neonatal hepatitis syndrome (NHS) by using a metabolomics method. We comprehensively analyzed the serum metabolites in a total of 124 blood samples from patients with BA or neonatal hepatitis syndrome (NHS) and from normal individuals using advanced metabolomic approaches, and found that the levels of glutarylcarnitine (C5DC) significantly increased in the BA group while the levels of threonine (Thr) significantly rose in the NHS group comparing with the other groups. The levels of glutamic acid (Glu) in the BA group were significantly elevated compared to those in the NHS group, but still lower than the hyperbilirubinemia and normal controls. The levels of propionyl carnitine (C3), isovaleryl carnitine (C5) and glutamine (Gln) were reduced in the BA group compared to those in the NHS group, but still higher than the hyperbilirubinemia and normal controls. This study demonstrates the possibility of metabolomics as non-invasive biomarkers for the early detection of BA and also provides new insight into pathophysiologic mechanisms for BA.

Newborn screening by tandem mass spectrometry for glutaric aciduria type 1: a cost-effectiveness analysis

BACKGROUND

Glutaric aciduria type I (GA-I) is a rare metabolic disorder caused by inherited deficiency of glutaryl-CoA dehydrogenase. Despite high prognostic relevance of early diagnosis and start of metabolic treatment as well as an additional cost saving potential later in life, only a limited number of countries recommend newborn screening for GA-I. So far only limited data is available enabling health care decision makers to evaluate whether investing into GA-I screening represents value for money. The aim of our study was therefore to assess the cost-effectiveness of newborn screening for GA-I by tandem mass spectrometry (MS/MS) compared to a scenario where GA-I is not included in the MS/MS screening panel.

METHODS

We assessed the cost-effectiveness of newborn screening for GA-I against the alternative of not including GA-I in MS/MS screening. A Markov model was developed simulating the clinical course of screened and unscreened newborns within different time horizons of 20 and 70 years. Monte Carlo simulation based probabilistic sensitivity analysis was used to determine the probability of GA-I screening representing a cost-effective therapeutic strategy.

RESULTS

Within a 20 year time horizon, GA-I screening averts approximately 3.7 DALYs (95% CI 2.9 - 4.5) and about one life year is gained (95% CI 0.7 - 1.4) per 100,000 neonates screened initially . Moreover, the screening programme saves a total of around 30,682 Euro (95% CI 14,343 to 49,176 Euro) per 100,000 screened neonates over a 20 year time horizon.

CONCLUSION

Within the limitations of the present study, extending pre-existing MS/MS newborn screening programmes by GA-I represents a highly cost-effective diagnostic strategy when assessed under conditions comparable to the German health care system.