Age at symptom onset predicts severity of motor impairment and clinical outcome of glutaric acidemia type 1

[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.

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.

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.

Does glutaric aciduria type 1 affect hearing function?

This study aimed to evaluate audiological findings among patients with glutaric aciduria type 1 (GA-1). We used a large test battery for the audiological evaluation of 17 individuals with GA-1 (the study group) and 20 healthy individuals (the control group). Conventional audiometry (0.125-8 kHz), distortion product otoacoustic emissions (DPOAEs) (1, 1.5, 2, 3, 4, 6, and 8 kHz), contralateral suppression of otoacoustic emissions, and auditory brainstem response (ABR) ( 30, 50, 70 and 90 dB nHL) were measured for all participants (n = 37). Mild sensorineural hearing loss was found in 77.47% (n = 13) of the patients with GA-1, and normal hearing thresholds were seen in 23.53% (n = 4). There were three asymptomatic patients at the time of diagnosis [two developed mild mental motor retardation (MMR) and one developed severe MMR during the follow-up], one with a normal hearing threshold and two with mild hearing loss), and 14 symptomatic patients (three with normal hearing thresholds and 11 with mild hearing loss). Seven of the symptomatic patients diagnosed following an encephalopathic crisis required intensive care and showed significantly worse hearing thresholds than those without symptoms [20.86 ± 4.47 vs. 15.44 ± 3.96 decibel hearing level (dB HL), p = 0.039*], while five had mild-to-moderate hearing loss. Acute encephalopathic crisis had a negative effect on hearing function in the symptomatic patients. The emission and contralateral suppression amplitude values of the study group were significantly lower compared to the control group (p < 0.05). The I-V interpeak latency and absolute latencies of ABR waves I, III, and V of the study group were observed to be significantly prolonged and morphologically distorted compared to those of the control group (p < 0.05). Five patients had MMR, and three had moderate MMR; all eight had mild-to-moderate hearing loss. In addition, of the eight patients with mild MMR, four had mild hearing loss. In particular, the morphological findings of ABR waves were significantly worse in the patients with severe and moderate MMR (p < 0.05). There was a significant correlation between a macrocephaly history (12 patients) and hearing loss (p = 0.041*). Magnetic resonance imaging findings were evaluated in all the 17 patients with GA-1, and typical fronto-temporal atrophy and sylvian fissure enlargement were observed. Our findings support that GA-1 is associated with auditory impairment, primarily in symptomatic patients. Adequate audiological test battery evaluation is essential in this context, particularly for symptomatic patients with a history of encephalopathic crises.

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.

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.

Evaluation of the Clinical, Biochemical, Neurological, and Genetic Presentations of Glutaric Aciduria Type 1 in Patients From China

Purpose

To characterize the phenotypic and genotypic variations associated with Glutaric aciduria type 1 (GA1) in Chinese patients.

Methods

We analyzed the clinical, neuroradiological, biochemical, and genetic information from 101 GA1 patients in mainland China.

Results

20 patients were diagnosed by newborn screening and the remaining 81 cases were identified following clinical intervention. Macrocephaly was the most common presentation, followed by movement disorders and seizures. A total of 59 patients were evaluated by brain MRI and 58 patients presented with abnormalities, with widening of the sylvian fissures being the most common symptom. The concentration of glutarylcarnitine in the blood, glutarylcarnitine/capryloylcarnitine ratio, and urine levels of glutaric acid were increased in GA1 patients and were shown to decrease following intervention. A total of 88 patient samples were available for genotyping and 74 variants within the GCDH gene, including 23 novel variants, were identified. The most common variant was c.1244-2A > C (18.4%) and there were no significant differences in the biochemical or clinical phenotypes described for patients with the four most common variants: c.1244-2A > C, c.1064G > A, c.533G > A, and c.1147C > T. Patients identified by newborn screening had better outcomes than clinical patients.

Conclusion

Our findings expand the spectrum of phenotypes and genotypes for GA1 in Chinese populations and suggest that an expanded newborn screening program using tandem mass spectrometry may facilitate the early diagnosis and treatment of this disease, improving clinical outcomes for patients in China.

Orthopaedic Problems in 35 Patients With Organic Acid Disorders

INTRODUCTION

Organic acid disorders (OADs) are a subset of inborn errors of metabolism that result in a toxic accumulation of organic acids in the body, which can lead to metabolic derangements and encephalopathy. Patients with these disorders are managed by a team of biochemical geneticists and metabolic nutritionists. However, subspecialists such as neurologists and orthopaedic surgeons are often needed to help manage the sequelae of the metabolic derangements. The breadth of orthopaedic sequelae of these disease states is poorly understood. Herein, we describe orthopaedic problems associated with 5 types of OAD most commonly seen at our institution: maple syrup urine disease, methylmalonic aciduria, propionic aciduria, pyruvate dehydrogenase deficiency, and glutaric aciduria type 1.

METHODS

We retrospectively reviewed medical records of 35 patients with an OAD who were seen at our academic tertiary care center from May 1999 to May 2020. Patients were grouped into cohorts according to OAD type and analyzed for orthopaedic presentations of hip, knee, or foot disorders, presence and severity of scoliosis, history of fracture, movement disorders, and osteopenia/osteoporosis.

RESULTS

Of the 35 patients, 13 had maple syrup urine disease, 12 had methylmalonic aciduria, 4 had propionic aciduria, 4 had pyruvate dehydrogenase deficiency, and 2 had glutaric aciduria type 1. Associated orthopaedic problems included spasticity causing neuromuscular scoliosis and/or hip subluxation or dislocation (10 patients), fractures (7 patients), and osteopenia/osteoporosis (7 patients). Overall, 22 of 35 patients had some orthopaedic condition.

CONCLUSIONS

Most in this cohort of patients with OAD also had an orthopaedic abnormality. It is important for physicians treating these patients to understand their propensity for musculoskeletal problems. When treating patients with OAD, it is important to initiate and maintain communication with specialists in several disciplines and to develop collaborative treatments for this unique population.

LEVEL OF EVIDENCE

Level IV-prognostic study.

Bilateral subdural hematomas and retinal hemorrhages mimicking nonaccidental trauma in a patient with D-2-hydroxyglutaric aciduria

INTRODUCTION

Nonaccidental trauma (NAT) is considered when pediatric patients present with intracranial injuries and a negative history of an accidental injury or concomitant medical diagnosis. The evaluation of NAT should include the consideration of possible medical causes including coagulation, hematologic, metabolic and other genetic disorders, as well as witnessed and unwitnessed accidental injuries.

CASE PRESENTATION

We present a 7-month-old male with spells and incidental findings of bilateral subdural hematomas, retinal hemorrhages, and secondary macrocephaly, leading to investigation for NAT. Biochemical analysis showed excretion of a large amount of D-2-hydroxyglutaric in urine consistent with a biochemical diagnosis of D-2-hydroxyglutaric aciduria, a rare neurometabolic disorder characterized by developmental delay, epilepsy, hypotonia, and psychomotor retardation. None of these symptoms were present in our patient at the time of diagnosis. Molecular genetic testing revealed a pathogenic splice site variant (c.685-2A>G) and a variant of uncertain significance (c.1256G>T) with evidence of pathogenicity in the D2HGDH gene, consistent with a molecular diagnosis of D-2-hydroxyglutaric aciduria type I (OMIM #600721).

CONCLUSION

Since several metabolic disorders, including D-2-hydroxyglutaric aciduria type I, can present solely with symptoms suggestive of NAT (subdural and retinal hemorrhages), an early metabolic evaluation by urine organic acid analysis should be included in clinical protocols evaluating NAT. A methodical and nonjudgmental approach coordinated between pediatricians and metabolic specialists is also necessary to ensure that rare genetic conditions are not overlooked to prevent devastating social, legal, and financial consequences of suspected child abuse.

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.

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.

Inborn Errors of Metabolism in the Emergency Department (Undiagnosed and Management of the Known)

An inborn error of metabolism should be considered in any neonate who presents to the emergency department in extremis and in any young child who presents with altered mental status and vomiting. In children with unknown diagnoses, it is crucial to draw the appropriate laboratory studies before the institution of therapy, although treatment needs rapid institution to mitigate neurologic damage and avoid worsening metabolic crisis. Although there are hundreds of individual genetic disorders, they are roughly placed into groups that present similarly. This article reviews the approach to the patient with unknown metabolic diagnosis and up-to-date management pearls for children with known disorders.

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.

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.

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.

Excessive homozygosity identified by chromosomal microarray at a known GCDH mutation locus correlates with brain MRI abnormalities in an infant with glutaric aciduria

Herein, we report a conceptually novel clinical case highlighting the diagnostic implications of excessive homozygosity and its correlation with brain MRI abnormalities in an infant with GA1. The case also points a need for an extra amount of caution to be exercised when evaluating patients with “negative exomes.”

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.

In Vivo NMR Studies of the Brain with Hereditary or Acquired Metabolic Disorders

Metabolic disorders, whether hereditary or acquired, affect the brain, and abnormalities of the brain are related to cellular integrity; particularly in regard to neurons and astrocytes as well as interactions between them. Metabolic disturbances lead to alterations in cellular function as well as microscopic and macroscopic structural changes in the brain with diabetes, the most typical example of metabolic disorders, and a number of hereditary metabolic disorders. Alternatively, cellular dysfunction and degeneration of the brain lead to metabolic disturbances in hereditary neurological disorders with neurodegeneration. Nuclear magnetic resonance (NMR) techniques allow us to assess a range of pathophysiological changes of the brain in vivo. For example, magnetic resonance spectroscopy detects alterations in brain metabolism and energetics. Physiological magnetic resonance imaging (MRI) detects accompanying changes in cerebral blood flow related to neurovascular coupling. Diffusion and T1/T2-weighted MRI detect microscopic and macroscopic changes of the brain structure. This review summarizes current NMR findings of functional, physiological and biochemical alterations within a number of hereditary and acquired metabolic disorders in both animal models and humans. The global view of the impact of these metabolic disorders on the brain may be useful in identifying the unique and/or general patterns of abnormalities in the living brain related to the pathophysiology of the diseases, and identifying future fields of inquiry.

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.

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.

Rare Late-Onset Presentation of Glutaric Aciduria Type I in a 16-Year-Old Woman with a Novel GCDH Mutation

Glutaric acidemia type I (GA-I) is a treatable autosomal recessive disorder of lysine, hydroxylysine, and tryptophan metabolism caused by glutaryl-CoA dehydrogenase (GCDH) deficiency. Presentation and progression of disease are variable ranging from asymptomatic carrier state to catastrophic encephalopathy. GA-I usually presents before age 18 months, usually triggered by childhood infection, with mild or severe acute encephalopathy, striatal degeneration, and movement disorder, most often acute dystonia. At a presymptomatic stage diagnosis is suggested clinically by macrocephaly, radiologically by widened Sylvian fissures and biochemically by the presence of excess 3-hydroxyglutaric acid and glutaric acid in urine. Treatment consists of lysine-restricted diet and carnitine supplementation, specific diet restrictions, as well as symptomatic and anticatabolic treatment of intercurrent illness. Presymptomatic diagnosis and treatment are essential to prognosis. We report the case of 16-year-old macrocephalic female with late-onset GA-I and unusual paucisymptomatic presentation with fainting after exercise and widespread white matter signal changes at MRI. She was compound heterozygote for a novel mutation (IVS10-2A>G) affecting splicing at GCDH and a common missense mutation (c. 1240C>T; p.Arg402Trp, R402W). Interestingly, the site of the novel mutation is the nucleotide position of a common mutation found almost exclusively in patients of Chinese/Taiwanese origin (IVS10-2A>C).

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

Patients with Glutaric aciduria type 1 (GA-1) can be identified by newborn screening using tandem mass spectrometry. The clinical evolution of screened patients seems to be more favourable compared with those diagnosed later, although long-term evolution is still doubtful. We have evaluated the outcome in nine GA-1 patients diagnosed in our region during 12 years. Six were detected by newborn screening and 3 clinically. The birth prevalence was 1:35,027. High blood C5DC concentration, in 8/9 patients, was found, whereas all patients exhibited high concentration of this metabolite in urine. Therefore, urine C5DC was a good marker for the detection of this disease. Eight different mutations in the GCDH gene were identified, four of them were novel (p.R88H, p.Y398C, p.R372K, p.D220N); being p.R227P the mostcommon. Macrocephaly with enlarged frontotemporal subarachnoid space was present in 4/6 patients diagnosed by newborn screening, all these patients required high energy intake, and in two cases, enteral feeding during the first year of life was needed. One child had an intercurrent episode of feeding refuse with hypoglycemia at two years of age. The mean follow-up time of screened patients was 56 months, and patients still remain asymptomatic. However, after a mean follow-up of 97 months treatment efficacy was poor in unscreened patients, two of them showing a severe spastic tetraparesis. Plasma levels of lysine, tryptophan and carnitine, were the most useful biomarkers for the follow-up. Our data support that, early diagnosis and treatment strategies are essential measures for the good clinical evolution of GA-1 patients.

Low lysine diet in glutaric aciduria type I--effect on anthropometric and biochemical follow-up parameters

BACKGROUND

Metabolic treatment in glutaric aciduria type I (GA-I) including a low lysine diet with lysine-free, tryptophan-reduced amino acid supplements (AAS), carnitine supplementation and early start of emergency treatment during putatively threatening episodes of intermittent febrile illness dramatically improves the outcome and thus has been recommended by an international guideline group (Kölker et al, J Inherit Metab Dis 30:5-22, 2007). However, possible affection of linear growth, weight gain and biochemical follow-up monitoring has not been studied systematically.

METHODS

Thirty-three patients (n = 29 asymptomatic, n = 4 dystonic) with GA-I who have been identified by newborn screening in Germany from 1999 to 2009 were followed prospectively during the first six years of life. Dietary treatment protocols, anthropometrical and biochemical parameters were longitudinally evaluated.

RESULTS

Mean daily intake as percentage of guideline recommendations was excellent for lysine (asymptomatic patients: 101 %; dystonic patients: 103 %), lysine-free, tryptophan-reduced AAS (108 %; 104 %), energy (106 %; 110 %), and carnitine (92 %; 102 %). Low lysine diet did not affect weight gain (mean SDS 0.05) but mildly impaired linear growth in asymptomatic patients (mean SDS -0.38), while dystonic patients showed significantly reduced weight gain (mean SDS -1.32) and a tendency towards linear growth retardation (mean SDS -1.03). Patients treated in accordance with recent recommendations did not show relevant abnormalities of routine biochemical follow-up parameters.

INTERPRETATION

Low lysine diet promotes sufficient intake of essential nutrients and anthropometric development in asymptomatic children up to age 6 year, whereas individualized nutritional concepts are required for dystonic patients. Revised recommendations for biochemical monitoring might be required for asymptomatic patients.

The peripartum management of a patient with glutaric aciduria type 1

The management of cesarean delivery for a parturient with placenta previa at 36 weeks' gestation and glutaric aciduria type 1 is presented. The management goal was to prevent encephalopathic crisis by ensuring adequate caloric intake with dextrose infusion and to provide carnitine supplementation and adequate anesthesia.

Glutaric aciduria type I: A treatable neurometabolic disorder

Background and Objectives:

Glutaric aciduria Type-I (GA-I) has characteristic clinical and neuroimaging features, which clinches the diagnosis in a majority of patients. However, there have been few case reports on GA-I from India. This study was undertaken to study the clinical presentations, metabolic profile, neuroimaging findings and outcome of patients with GA-I.

Study Design:

The present study was a retrospective study.

Materials and Methods:

Retrospective review of charts of patients with a diagnosis of GA-I was carried out from March 2008 to April 2010. The clinical, laboratory and neuroimaging findings were extracted in a predesigned proforma and the data was analyzed.

Results:

Eleven cases were found to have GA-1. Clinical presentation was quite varied. Follow-up of patients revealed that one patient with macrocephaly as the only clinical finding was developmentally normal. One patient with encephalitis-like illness steadily improved and started walking at 2 years. Two patients were bed ridden and had severe dystonia. One patient died during follow-up. The remaining six patients had dystonia and other abnormal movements, but had attained sitting without support and were not ambulatory.

Conclusion:

GA-I is not an uncommon disorder and diagnosis can be made easily based on clinical, laboratory investigations and neuroimaging findings. It is one of the treatable metabolic disorders and, if managed appropriately, favorable prognosis can be given.

Carnitine supplementation for inborn errors of metabolism

BACKGROUND

Inborn errors of metabolism are genetic conditions which can lead to abnormalities in the synthesis and metabolism of proteins, carbohydrates, or fats. It has been proposed that in some instances carnitine supplementation should be provided to infants with a suspected metabolic disease as an interim measure, particularly whilst awaiting test results. Carnitine supplementation is used in the treatment of primary carnitine deficiency, and also where the deficiency is a secondary complication of several inborn errors of metabolism, such as organic acidaemias and fatty acid oxidation defects in children and adults.

OBJECTIVES

To assess the effectiveness and safety of carnitine supplementation in the treatment of inborn errors of metabolism.

SEARCH METHODS

We searched the Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register, the Cochrane Central Register of Controlled Trials (The Cochrane Library 2007, Issue 4) and MEDLINE via Ovid (1950 to July week 4 2007), LILACS (15/05/2008) and Iranmedex (15/05/2008) and also the reference lists of retrieved articles.Date of most recent search of the Group's Inborn Errors of Metabolism Register: 27 October 2011.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing carnitine supplementation (in different dose, frequency, or duration) versus placebo in children and adults diagnosed with an inborn error of metabolism.

DATA COLLECTION AND ANALYSIS

Two authors independently screened and assessed the eligibility of the identified trials.

MAIN RESULTS

No trials were included in the review.

AUTHORS' CONCLUSIONS

There are no published or ongoing randomised controlled clinical trials relevant to this review question. Therefore, in the absence of any high level evidence, clinicians should base their decisions on clinical experience and in conjunction with preferences of the individual where appropriate. This does not mean that carnitine is ineffective or should not be used in any inborn error of metabolism. However, given the lack of evidence both on the effectiveness and safety of carnitine and on the necessary dose and frequency to be prescribed, the current prescribing practice should continue to be observed and monitored with care until further evidence is available. Methodologically sound trials, reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement, are required. It should be considered whether placebo-controlled trials in potentially lethal diseases, e.g. carnitine transporter disorder or glutaric aciduria type I, are ethical.

Diagnosis, treatment and outcome of glutaric aciduria type I in Zhejiang Province, China

Background

Glutaric aciduria type I (GA I; MIM 231670) is a rare autosomal recessive disorder resulting from glutaryl-CoA dehydrogenase deficiency. This article reports our experience in the diagnosis, treatment and outcome of GA I patients in Zhejiang Province, China.

Material/Methods

A total of 129,415 newborns (accounting for approximately one-tenth of the annual births in Zhejiang Province) and 9640 high-risk infants were screened for inborn errors of metabolism in the Neonatal Screening Center of Zhejiang Province during a 3-year period. Tandem mass spectrometry and gas chromatography-mass spectrometry were used for diagnosis of the patients. Dietary modification, carnitine supplementation and aggressive treatment of intercurrent illnesses were adapted for GA I patients.

Results

Three infants were diagnosed with GA I by high-risk screening (detection rate: 1/3,213) and 2 were diagnosed by newborn screening (incidence: 1/64,708). Four patients (3 by high-risk screening and 1 by neonatal screening) undergoing MRI examination showed remarkable changes on T2-weighted image. Four patients accepted timely treatment, and in the patient diagnosed by neonatal screening, treatment was delayed until hypotonia appeared 3 months later. Neuropsychological assessment showed mental and motor retardation in 3 patients after treatment, including the patient diagnosed by neonatal screening.

Conclusions

Individualized timely treatment and close monitoring of GA I patients needs to be optimized in China. Appropriate communication with parents may help to achieve successful management of GA I patients.

Diagnosis and management of glutaric aciduria type I--revised recommendations

Glutaric aciduria type I (synonym, glutaric acidemia type I) is a rare organic aciduria. Untreated patients characteristically develop dystonia during infancy resulting in a high morbidity and mortality. The neuropathological correlate is striatal injury which results from encephalopathic crises precipitated by infectious diseases, immunizations and surgery during a finite period of brain development, or develops insidiously without clinically apparent crises. Glutaric aciduria type I is caused by inherited deficiency of glutaryl-CoA dehydrogenase which is involved in the catabolic pathways of L-lysine, L-hydroxylysine and L-tryptophan. This defect gives rise to elevated glutaric acid, 3-hydroxyglutaric acid, glutaconic acid, and glutarylcarnitine which can be detected by gas chromatography/mass spectrometry (organic acids) or tandem mass spectrometry (acylcarnitines). Glutaric aciduria type I is included in the panel of diseases that are identified by expanded newborn screening in some countries. It has been shown that in the majority of neonatally diagnosed patients striatal injury can be prevented by combined metabolic treatment. Metabolic treatment that includes a low lysine diet, carnitine supplementation and intensified emergency treatment during acute episodes of intercurrent illness should be introduced and monitored by an experienced interdisciplinary team. However, initiation of treatment after the onset of symptoms is generally not effective in preventing permanent damage. Secondary dystonia is often difficult to treat, and the efficacy of available drugs cannot be predicted precisely in individual patients. The major aim of this revision is to re-evaluate the previous diagnostic and therapeutic recommendations for patients with this disease and incorporate new research findings into the guideline.

Clinical and molecular investigation of 19 Japanese cases of glutaric acidemia type 1

Glutaric acidemia type 1 (GA1) is a metabolic disease caused by a deficiency of glutaryl-CoA dehydrogenase (GCDH). Untreated patients mostly develop severe striatal degeneration. More than 200 mutations have been reported in the GCDH gene, and common R402W and IVS10-2A>C were found in Caucasian and Chinese/Taiwanese, respectively. However, in Japan, genetic mutations have only been reported in a few cases. Herein, we report the clinical and molecular basis of GA1 in 19 Japanese patients, including six previously reported patients. All cases showed high urinary glutaric acid excretion. Eleven patients were severely impaired (three patients died), three had mild impairment, and five showed normal development. Four of 5 patients that developed normally were detected in the presymptomatic stage by neonatal or sibling screening. Nineteen mutations in 26 alleles were identified, and eight of them (89 or 90delC, Y155C, IVS4+2T＞C, G244S, Q352X, G354A, K361E, and 1144-1145delGC) were novel. S305L (12.1%, 4/34 alleles) was found in several cases, suggesting that this mutation is a common mutation. In contrast, R402W was not identified and IVS10-2A>C was only found in one allele, suggesting that Japanese patients with GA1 show allelic heterogeneity and have a different genetic background to patients from other countries. One of a pair of sisters with the same mutations (M339V/S305L) lacking residual activity was severely retarded, whereas the older girl remains asymptomatic at 22 years of age, indicating that genotype does not necessarily predict GA1 phenotype. We consistently found that there was no association between genotype and phenotype. However, children with mild impairment were diagnosed and treated earlier than severely impaired cases {4.7±2.5 months (range: 2-8 months) vs. 11.6±12.7 months (range: 4-51 months)}. Our results suggest that early detection and treatment but not genotype are associated with better patient outcome, reinforcing the importance of neonatal screening.

Enzymatic evaluation of glutaric acidemia type 1 by an in vitro probe assay of acylcarnitine profiling using fibroblasts and electrospray ionization/tandem mass spectrometry (MS/MS)

Glutaric acidemia type 1 (GA1) is usually diagnosed with an accumulation of glutaric acid (GA) or 3-hydroxyglutaric acid by GC/MS. In some cases, however, excretion of GA is low. We investigated enzymatic evaluation of GA1 using fibroblasts and MS/MS. After loading substrates, lysine, 2-aminoadipate (2AA), or GA, in fibroblasts, and incubating for 96 h, glutarylcarnitine (C5DC) levels in the media were measured. A significant increase of C5DC was observed in GA1 patients, irrespective of substrates added. 2AA showed the largest difference between patients and controls (p = 0.0004). Results suggested enzymatic evaluation of GA1 is useful under appropriate culture conditions.

Carnitine supplementation for inborn errors of metabolism

BACKGROUND

Inborn errors of metabolism are genetic conditions which can lead to abnormalities in the synthesis and metabolism of proteins, carbohydrates, or fats. It has been proposed that in some instances carnitine supplementation should be provided to infants with a suspected metabolic disease as an interim measure, particularly whilst awaiting test results. Carnitine supplementation is used in the treatment of primary carnitine deficiency, and also where the deficiency is a secondary complication of several inborn errors of metabolism, such as organic acidaemias and fatty acid oxidation defects in children and adults.

OBJECTIVES

To assess the effectiveness and safety of carnitine supplementation in the treatment of inborn errors of metabolism.

SEARCH STRATEGY

We searched the Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register, the Cochrane Central Register of Controlled Trials (The Cochrane Library 2007, Issue 4) and MEDLINE via Ovid (1950 to July week 4 2007), LILACS (15/05/2008) and Iranmedex (15/05/2008) and also the reference lists of retrieved articles.Date of most recent search of the Group's Inborn Errors of Metabolism Register: 27 October 2008.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing carnitine supplementation (in different dose, frequency, or duration) versus placebo in children and adults diagnosed with an inborn error of metabolism.

DATA COLLECTION AND ANALYSIS

Two authors independently screened and assessed the eligibility of the identified trials.

MAIN RESULTS

No trials were included in the review.

AUTHORS' CONCLUSIONS

There are no published or ongoing randomised controlled clinical trials relevant to this review question. Therefore, in the absence of any high level evidence, clinicians should base their decisions on clinical experience and in conjunction with preferences of the individual where appropriate. This does not mean that carnitine is ineffective or should not be used in any inborn error of metabolism. However, given the lack of evidence both on the effectiveness and safety of carnitine and on the necessary dose and frequency to be prescribed, the current prescribing practice should continue to be observed and monitored with care until further evidence is available. Methodologically sound trials, reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement, are required. It should be considered whether placebo-controlled trials in potentially lethal diseases, e.g. carnitine transporter disorder or glutaric aciduria type I, are ethical.

Decline of acute encephalopathic crises in children with glutaryl-CoA dehydrogenase deficiency identified by newborn screening in Germany

Glutaryl-CoA dehydrogenase (GCDH) deficiency is a rare neurometabolic disorder that is considered treatable if patients are identified before the onset of acute encephalopathic crises. To allow early identification of affected individuals, tandem mass spectrometry-based newborn screening for GCDH deficiency has been started in Germany in 1999. We prospectively followed neonatally screened patients (n=38) and compared the neurologic outcome with patients from a historical cohort (n=62). In the majority of neonatally screened children, the onset of encephalopathic crises has been prevented (89%), whereas acute encephalopathic crises or progressive neurologic impairment was common in the historical cohort. Neonatal screening in combination with intensive management is effective--even assuming ascertainment bias in the historical cohort. Similar proportions of commonest mutations and biochemical phenotypes (high and low excretors) were found in neonatally screened and historical patients. However, potential predictor variables for mild clinical phenotypes are not yet known and thus a selection of these patients by newborn screening is not excluded. No patient was known to be missed by newborn screening from 1999 to 2005. In conclusion, this study confirms that newborn screening for GCDH deficiency in combination with intensive management is beneficial.

Age and brain structural related effects of glutaric and 3-hydroxyglutaric acids on glutamate binding to plasma membranes during rat brain development

(1) In the present study we determined the effects of glutaric (GA, 0.01-1 mM) and 3-hydroxyglutaric (3-OHGA, 1.0-100 microM) acids, the major metabolites accumulating in glutaric acidemia type I (GA I), on Na(+)-independent and Na(+)-dependent [(3)H]glutamate binding to synaptic plasma membranes from cerebral cortex and striatum of rats aged 7, 15 and 60 days. (2) GA selectively inhibited Na(+)-independent [(3)H]glutamate binding (binding to receptors) in cerebral cortex and striatum of rats aged 7 and 15 days, but not aged 60 days. In contrast, GA did not alter Na(+)-dependent glutamate binding (binding to transporters) to synaptic membranes from brain structures of rats at all studied ages. Furthermore, experiments using the glutamatergic antagonist CNQX indicated that GA probably binds to non-NMDA receptors. In addition, GA markedly inhibited [(3)H]kainate binding to synaptic plasma membranes in cerebral cortex of 15-day-old rats, indicating that this effect was probably directed towards kainate receptors. On the other hand, experiments performed with 3-OHGA revealed that this organic acid did not change Na(+)-independent [(3)H]glutamate binding to synaptic membranes from cerebral cortex and striatum of rats from all ages, but inhibited Na(+)-dependent [(3)H]glutamate binding to membranes in striatum of 7-day-old rats, but not in striatum of 15- and 60-day-old rats and in cerebral cortex of rats from all studied ages. We also provided some evidence that 3-OHGA competes with the glutamate transporter inhibitor L-trans-pyrrolidine-2,4-dicarboxylate, suggesting a possible interaction of 3-OHGA with glutamate transporters on synaptic membranes. (3) These results indicate that glutamate binding to receptors and transporters can be inhibited by GA and 3-OHGA in cerebral cortex and striatum in a developmentally regulated manner. It is postulated that a disturbance of glutamatergic neurotransmission caused by the major metabolites accumulating in GA I at early development may possibly explain, at least in part, the window of vulnerability of striatum and cerebral cortex to injury in patients affected by this disorder.

The cost-effectiveness of expanding newborn screening for up to 21 inherited metabolic disorders using tandem mass spectrometry: results from a decision-analytic model

OBJECTIVES

In 2005, in Ontario, Canada, newborns were only screened for phenylketonuria (PKU) and hypothyroidism. Tandem mass spectrometry (MS/MS) has since been implemented as a new screening technology because it can screen for PKU and many other diseases simultaneously. We estimated the cost-effectiveness of using this technology to expand the Ontario newborn screening program to screen for each disease independently and for hypothetical bundles of up to 21 metabolic diseases.

METHODS

We constructed a decision-analytic model to estimate the incremental costs and life-years of survival that can be gained by screening or changing screening technologies. Costs and health benefits were estimated for a cohort of babies born in Ontario in 1 year. Secondary sources and expert opinion were used to estimate the test characteristics, disease prevalence, treatment effectiveness, disease progression rates, and mortality. The London Health Sciences Centre Case Costing Initiative, the Ontario Health Insurance Plan Schedule, and the Ontario Drug Benefits plan formulary were used to estimate costs.

RESULTS

Changing screening technologies, from the Guthrie test to MS/MS, for PKU detection had an incremental cost of $5,500,000 per life-year (LY) gained. We identified no diseases for which the incremental cost of screening for just that disease was less than $100,000 per LY gained. The incremental costs of screening ranged from $222,000 (HMG-CoA lyase deficiency) to $142,500,000 (glutaric acidemia type II) per LY gained. Screening for a bundle of diseases including PKU and the 14 most cost-effective diseases to screen for cost less than $70,000 per LY gained, and the incremental cost-effectiveness of adding each of the 14 diseases to the bundle was less than $100,000 per LY gained. The incremental cost of adding the 15th most cost-effective disease was $309,400 per LY gained.

CONCLUSIONS

Early diagnosis and treatment of metabolic disease is important to reduce disease severity and delay or prevent the onset of the disease. Screening at birth reduces the morbidity, mortality, and social burden associated with the irreversible effects of disease on the population. Our analysis suggests that the cost-efficiencies gained by using MS/MS to screen for bundles of diseases rather than just one disease are sufficient to warrant consideration of an expanded screening program. It is, however, not cost-effective to screen for all diseases that can be screened for using this technology.

Guideline for the diagnosis and management of glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type I)

Glutaryl-CoA dehydrogenase (GCDH) deficiency is an autosomal recessive disease with an estimated overall prevalence of 1 in 100 000 newborns. Biochemically, the disease is characterized by accumulation of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid, and glutarylcarnitine, which can be detected by gas chromatography-mass spectrometry of organic acids or tandem mass spectrometry of acylcarnitines. Clinically, the disease course is usually determined by acute encephalopathic crises precipitated by infectious diseases, immunizations, and surgery during infancy or childhood. The characteristic neurological sequel is acute striatal injury and, subsequently, dystonia. During the last three decades attempts have been made to establish and optimize therapy for GCDH deficiency. Maintenance treatment consisting of a diet combined with oral supplementation of L: -carnitine, and an intensified emergency treatment during acute episodes of intercurrent illness have been applied to the majority of patients. This treatment strategy has significantly reduced the frequency of acute encephalopathic crises in early-diagnosed patients. Therefore, GCDH deficiency is now considered to be a treatable condition. However, significant differences exist in the diagnostic procedure and management of affected patients so that there is a wide variation of the outcome, in particular of pre-symptomatically diagnosed patients. At this time of rapid expansion of neonatal screening for GCDH deficiency, the major aim of this guideline is to re-assess the common practice and to formulate recommendations for diagnosis and management of GCDH deficiency based on the best available evidence.

Infant mice with glutaric acidaemia type I have increased vulnerability to 3-nitropropionic acid toxicity

Glutaric acidaemia type I (GA I) is an inborn error of metabolism caused by a deficiency of glutaryl-CoA dehydrogenase (GCDH) and is characterized clinically by striatal degeneration that almost always occurs in early childhood. A murine knockout model of GA I has the organic aciduria seen in the human disorder, but this model does not develop striatal degeneration spontaneously. 3-Nitropropionic acid (3NP), a succinic dehydrogenase inhibitor with specificity for the striatum, was investigated as a potential initiator of striatal degeneration in GCDH-deficient mice. This study shows that GCDH-deficient mouse pups are more susceptible to 3NP than their wild-type littermates, and that all mouse pups are more sensitive to 3NP as infants than as adolescents and adults. Increased sensitivity to 3NP early in life may model the developmental window for the striatal damage observed in human GA I.

L’acidurie glutarique type I : une cause méconnue de dystonie progressive

INTRODUCTION

Glutaric acidemia type I is one of the least rare organic acidemias. The number of diagnosed causes is however still low because the presentation is variable and often confusing. The disease may sometimes have a slowly progressive course. Typically, it presents in infancy, mimicking acute encephalitis, leaving a previously healthy child severely handicapped with generalized dystonia, spastic quadriplegia or choreoathetosis. Cerebral MRI shows large CSF-containing spaces (sylvian fissures and anterior to the temporal lobes) and basal ganglia abnormal signal.

CASE REPORT

An eight year-old boy had begun at 18 months with motor difficulties and abnormal posture of upper and lower left limbs. When examined, he had generalized dystonia more pronounced at the left side, severe dysarthria and tongue dystonia. IQ was normal. MRI showed high T2 signal in basal ganglia and enlarged CSF containing spaces. Urinary organic acids chromatography confirmed glutaric acidemia type I. Two of his sisters deceased before the age of two years with a clinical picture of fever, seizures and hypotonia. Another sister had the same symptoms at the same age. She lived until 10 year with severe quadriplegia.

COMMENTS

Our observation shows variability of clinical picture and course of glutaric acidemia type I in the same kindred. We propose systematic organic acides chromatography in all children with acute or progressive dystonia with basal ganglia abnormalities on MRI. This seems an imperative attitude because appropriate diet could slow the progression of the illness.

Natural history, outcome, and treatment efficacy in children and adults with glutaryl-CoA dehydrogenase deficiency

Glutaryl-CoA dehydrogenase (GCDH) deficiency is a rare inborn disorder of L-lysine, L-hydroxylysine, and L-tryptophan metabolism complicated by striatal damage during acute encephalopathic crises. Three decades after its description, the natural history and how to treat this disorder are still incompletely understood. To study which variables influenced the outcome, we conducted an international cross-sectional study in 35 metabolic centers. Our main outcome measures were onset and neurologic sequelae of acute encephalopathic crises. A total of 279 patients (160 male, 119 female) were included who were diagnosed clinically after clinical presentation (n = 218) or presymptomatically by neonatal screening (n = 23), high-risk screening (n = 24), or macrocephaly (n = 14). Most symptomatic patients (n = 185) had encephalopathic crises, characteristically resulting in bilateral striatal damage and dystonia, secondary complications, and reduced life expectancy. First crises usually occurred during infancy (95% by age 2 y); the oldest age at which a repeat crisis was reported was 70 mo. In a few patients, neurologic disease developed without a reported crisis. Differences in the diagnostic criteria and therapeutic protocols for patients with GCDH deficiency resulted in a huge variability in the outcome worldwide. Recursive partitioning demonstrated that timely diagnosis in neurologically asymptomatic patients followed by treatment with L-carnitine and a lysine-restricted diet was the best predictor of good outcome, whereas treatment efficacy was low in patients diagnosed after the onset of neurologic disease. Notably, the biochemical phenotype did not predict the clinical phenotype. Our study proves GCDH deficiency to be a treatable disorder and a good candidate for neonatal screening.

Neonatal screening for glutaric aciduria type I: strategies to proceed

Acute encephalopathic crisis in glutaric aciduria type I results in an unfavourable disease course and poor outcome, dominated by dystonia, feeding problems, seizures and reduced life expectancy. A conditio sine qua non for the prevention of irreversible brain damage is timely diagnosis and start of therapy, i.e. before the onset of neurological disease. As there are no specific clinical signs or symptoms that allow a reliable detection of these patients before the manifestation of encephalopathic crises, neonatal screening programmes for glutaric aciduria type I have been established in some countries using analysis of glutarylcarnitine in dried blood spots by tandem mass spectrometry. This article summarizes recent strategies, pitfalls and shortcomings of mass screening for glutaric aciduria type I, focusing on the relevant risk of missing patients with a mild biochemical phenotype (i.e. low excretors). Furthermore, it evaluates a binary strategy--using glutarylcarnitine as primary variable and glutarylcarnitine/acylcarnitine ratios as secondary variable--to improve the diagnostic sensitivity and specificity of neonatal screening for glutaric aciduria type I. An optimization of diagnostic as well as therapeutic procedures must be achieved before screening for glutaric aciduria type I can be regarded as reliable and beneficial for all patients.

Quantification of glutaric and 3-hydroxyglutaric acids in urine of glutaric acidemia type I patients by HPLC with intramolecular excimer-forming fluorescence derivatization

BACKGROUND

Glutaric aciduria type I (GA1) is an autosomal recessive disorder that usually causes neurological damage. Early diagnosis of the disease prior to the appearance of clinical symptoms can lead to better outcomes.

METHODS

We describe a simple and selective HPLC method with intramolecular excimer-forming fluorescence derivatization to diagnose GA1. Glutaric acid (GA) and 3-hydroxyglutaric acid (3HGA) in urine and an internal standard were derivatized with 1-pyrenebutyric hydrazide (PBH). The derivatives were separated on a C18 column and fluorometrically detected at 475 nm (excitation of 345 nm) with a run time of 18 min.

RESULTS

Excellent linearity over a wide range, reproducibility (coefficient of variation < or =14.5%), and sensitivity (limit of detection 0.4 micromol/l 3HGA and 0.2 micromol/l GA) were obtained. A retrospective study on previously diagnosed GA1 patients' urine from our laboratory archives between 1999 and 2004 was performed by analysts blinded to the study.

CONCLUSIONS

The method enabled us to differentiate GA1 cases (n=36) from controls (n=99), regardless of the years of urine storage. The method is valuable for both retrospective and prospective diagnoses of GA1.

Late-onset neurologic disease in glutaryl-CoA dehydrogenase deficiency

Neurologic disease in glutaryl-CoA dehydrogenase (GCDH) deficiency usually presents with acute encephalopathic crises before 2 years of age. The authors report two previously asymptomatic patients with macrocephaly presenting with progressive neurologic deterioration and a severe leukoencephalopathy during adolescence or adulthood.