Dynamic changes of striatal and extrastriatal abnormalities in glutaric aciduria type I

Reversible brain atrophy in glutaric aciduria type 1

Glutaric aciduria type 1 (GA1) is a rare metabolic disorder caused by a deficiency of glutaryl-CoA dehydrogenase. The typical clinical onset features an acute encephalopathic crisis developed in early childhood, causing irreversible striatal injury. Recently, tandem mass spectrometry of spots of dried blood has allowed pre-symptomatic detection of GA1 in newborns. Early treatment can prevent irreversible neurological injury. We report the case of a girl with GA1 who exhibited a characteristic reversible change upon brain magnetic resonance imaging (MRI). She was diagnosed with GA1 as a newborn. She commenced dietary carnitine and her intake of lysine and tryptophan were reduced at the age of 4weeks. After treatment commenced, her mean glutarylcarnitine level was lower than that in the previous reports. The plasma lysine and tryptophan levels were maintained below the normal ranges. At 4months, brain MRI revealed a widened operculum with dilatation of the subarachnoid spaces surrounding the atrophic bilateral frontotemporal lobes; this is typical of GA1 patients. However, at 17months, MRI revealed that the atrophic lesion had disappeared and she subsequently underwent normal maturation. She has never suffered a metabolic decompensation episode. At 26months, her development and brain MRI were normal. The present reversible brain atrophy in a patient with GA1 indicates that early dietary modifications with a lower level of glutarylcarnitine and administration of carnitine can lead to normal development.

Elevated glutaric acid levels in Dhtkd1-/Gcdh- double knockout mice challenge our current understanding of lysine metabolism

Glutaric aciduria type I (GA-I) is a rare organic aciduria caused by the autosomal recessive inherited deficiency of glutaryl-CoA dehydrogenase (GCDH). GCDH deficiency leads to disruption of l-lysine degradation with characteristic accumulation of glutarylcarnitine and neurotoxic glutaric acid (GA), glutaryl-CoA, 3-hydroxyglutaric acid (3-OHGA). DHTKD1 acts upstream of GCDH, and its deficiency leads to none or often mild clinical phenotype in humans, 2-aminoadipic 2-oxoadipic aciduria. We hypothesized that inhibition of DHTKD1 may prevent the accumulation of neurotoxic dicarboxylic metabolites suggesting DHTKD1 inhibition as a possible treatment strategy for GA-I. In order to validate this hypothesis we took advantage of an existing GA-I (Gcdh^-/-) mouse model and established a Dhtkd1 deficient mouse model. Both models reproduced the biochemical and clinical phenotype observed in patients. Under challenging conditions of a high lysine diet, only Gcdh^-/- mice but not Dhtkd1^-/- mice developed clinical symptoms such as lethargic behaviour and weight loss. However, the genetic Dhtkd1 inhibition in Dhtkd1^-/-/Gcdh^-/- mice could not rescue the GA-I phenotype. Biochemical results confirm this finding with double knockout mice showing similar metabolite accumulations as Gcdh^-/- mice with high GA in brain and liver. This suggests that DHTKD1 inhibition alone is not sufficient to treat GA-I, but instead a more complex strategy is needed. Our data highlights the many unresolved questions within the l-lysine degradation pathway and provides evidence for a so far unknown mechanism leading to glutaryl-CoA.

Extrastriatal changes in patients with late-onset glutaric aciduria type I highlight the risk of long-term neurotoxicity

BACKGROUND

Without neonatal initiation of treatment, 80-90% of patients with glutaric aciduria type 1 (GA1) develop striatal injury during the first six years of life resulting in a complex, predominantly dystonic movement disorder. Onset of motor symptoms may be acute following encephalopathic crisis or insidious without apparent crisis. Additionally, so-called late-onset GA1 has been described in single patients diagnosed after the age of 6 years. With the aim of better characterizing and understanding late-onset GA1 we analyzed clinical findings, biochemical phenotype, and MRI changes of eight late-onset patients and compared these to eight control patients over the age of 6 years with early diagnosis and start of treatment.

RESULTS

No late-onset or control patient had either dystonia or striatal lesions on MRI. All late-onset (8/8) patients were high excretors, but only four of eight control patients. Two of eight late-onset patients were diagnosed after the age of 60 years, presenting with dementia, tremor, and epilepsy, while six were diagnosed before the age of 30 years: Three were asymptomatic mothers identified by following a positive screening result in their newborns and three had non-specific general symptoms, one with additional mild neurological deficits. Frontotemporal hypoplasia and white matter changes were present in all eight and subependymal lesions in six late-onset patients. At comparable age a greater proportion of late-onset patients had (non-specific) clinical symptoms and possibly subependymal nodules compared to control patients, in particular in comparison to the four clinically and MR-wise asymptomatic low-excreting control patients.

CONCLUSIONS

While clinical findings are non-specific, frontotemporal hypoplasia and subependymal nodules are characteristic MRI findings of late-onset GA1 and should trigger diagnostic investigation for this rare disease. Apart from their apparent non-susceptibility for striatal injury despite lack of treatment, patients with late-onset GA1 are not categorically different from early treated control patients. Differences between late-onset patients and early treated control patients most likely reflect greater cumulative neurotoxicity in individuals remaining undiagnosed and untreated for years, even decades as well as the higher long-term risk of high excretors for intracerebral accumulation of neurotoxic metabolites compared to low excretors.

Glutaric Acidemia Type 1: A Case of Infantile Stroke

BACKGROUND

Glutaric acidemia Type 1 (GA-1) is an autosomal recessively inherited metabolic disorder which is associated with GCDH gene mutations which alters the glutaryl-CoA dehydrogenase, an enzyme playing role in the catabolic pathways of the amino acids lysine, hydroxylysine, and tryptophan. Clinical findings are often encephalopathic crises, dystonia, and extrapyramidal symptoms.

CASE REPORT

A 9-month-old male infant referred to our department with focal tonic-clonic seizures during rotavirus infection and acute infarcts in MRI. Clinical manifestation, MRI findings, and metabolic investigations directed thoughts towards GA-I. Molecular genetic testing revealed a homozygous c.572T>C (p.M191T) mutation in GCDH gene which confirmed the diagnosis. Application of protein restricted diet, carnitine and riboflavin supplementations prevented the progression of Magnetic Resonance Imaging (MRI) and clinical pathologic findings during the 1 year of follow-up period.

CONCLUSION

This case is of great importance since it shows possibility of infantile stroke in GA-1, significance of early diagnosis and phenotypic variability of disease.

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.

Severe Acute Subdural Hemorrhages in a Patient with Glutaric Acidemia Type 1 under Recommended Treatment

Glutaric acidemia type 1 is a rare autosomal recessive disease caused by a deficiency of glutaryl-CoA dehydrogenase. Previous studies have reported subdural hemorrhage in untreated patients with glutaric acidemia type 1. However, there is only one report of severe acute subdural hemorrhage after minor head trauma in a patient with glutaric acidemia type 1 under guideline-recommended treatment. We report a second case of life-threatening severe acute subdural hemorrhage after a minor head trauma in a patient with glutaric acidemia type 1. This patient was previously diagnosed by newborn screening, and treatment began at 25 days of age. Early diagnosis and guideline-recommended treatment produce better outcomes for patients with glutaric acidemia type 1, although the risk of subdural hemorrhage remains.

Neurological Disorders Associated with Striatal Lesions: Classification and Diagnostic Approach

Neostriatal abnormalities can be observed in a very large number of neurological conditions clinically dominated by the presence of movement disorders. The neuroradiological picture in some cases has been described as "bilateral striatal necrosis" (BSN). BSN represents a condition histo-pathologically defined by the involvement of the neostriata and characterized by initial swelling of putamina and caudates followed by degeneration and cellular necrosis. After the first description in 1975, numerous acquired and hereditary conditions have been associated with the presence of BSN. At the same time, a large number of disorders involving neostriata have been described as BSN, in some cases irrespective of the presence of signs of cavitation on MRI. As a consequence, the etiological spectrum and the nosographic boundaries of the syndrome have progressively become less clear. In this study, we review the clinical and radiological features of the conditions associated with MRI evidence of bilateral striatal lesions. Based on MRI findings, we have distinguished two groups of disorders: BSN and other neostriatal lesions (SL). This distinction is extremely helpful in narrowing the differential diagnosis to a small group of known conditions. The clinical picture and complementary exams will finally lead to the diagnosis. We provide an update on the etiological spectrum of BSN and propose a diagnostic flowchart for clinicians.

Nomenclature of genetic movement disorders: Recommendations of the international Parkinson and movement disorder society task force

The system of assigning locus symbols to specify chromosomal regions that are associated with a familial disorder has a number of problems when used as a reference list of genetically determined disorders,including (I) erroneously assigned loci, (II) duplicated loci, (III) missing symbols or loci, (IV) unconfirmed loci and genes, (V) a combination of causative genes and risk factor genes in the same list, and (VI) discordance between phenotype and list assignment. In this article, we report on the recommendations of the International Parkinson and Movement Disorder Society Task Force for Nomenclature of Genetic Movement Disorders and present a system for naming genetically determined movement disorders that addresses these problems. We demonstrate how the system would be applied to currently known genetically determined parkinsonism, dystonia, dominantly inherited ataxia, spastic paraparesis, chorea, paroxysmal movement disorders, neurodegeneration with brain iron accumulation, and primary familial brain calcifications. This system provides a resource for clinicians and researchers that, unlike the previous system, can be considered an accurate and criterion-based list of confirmed genetically determined movement disorders at the time it was last updated.

Occurrence of subdural hematomas in Dutch glutaric aciduria type 1 patients

Patients with glutaric aciduria type 1 (GA1), a rare inherited metabolic disorder, have an increased risk for subdural hematomas (SDHs). GA1 is therefore generally included in the differential diagnosis of children presenting with SDHs. This retrospective cohort study reviews all 25 registered, in the Dutch Diagnosis Registration for Metabolic Disorders, GA1 patients in the Netherlands. This was done between May 2014 and November 2014 to determine the lifetime incidence of SDHs in this population. Seventeen patients were diagnosed either due to clinical symptoms or because of family members with GA1. One out of these 17 had a SDH. This patient showed widened Sylvian fissures on MRI, characteristic for GA1. Eight patients were diagnosed by newborn screening. Three of them had neuroimaging results, and none of them had SDHs. This study shows an overall lower incidence (4.0 %) of SDHs in patients with GA1 than reported in the literature (20-30 %).

CONCLUSION

This finding, in combination with the fact that SDHs in GA1 appear to occur only in the presence of characteristic brain abnormalities on imaging, we recommend that GA1 should not routinely be a part of the differential diagnosis of children with unexplained SDHs in the absence of imaging characteristics suggestive of GA1.

WHAT IS KNOWN

• Glutaric aciduria type 1 is a rare metabolic disorder predisposing children to subdural hematoma development due to brain abnormalities. • Because of these subdural hematomas, glutaric aciduria type 1 testing is part of abusive head trauma work-up. What is new: • The overall subdural hematoma incidence in glutaric aciduria type 1 patients is much lower than previously reported and only occurs in case of predisposing brain abnormalities.

A cross-sectional controlled developmental study of neuropsychological functions in patients with glutaric aciduria type I

Background

Glutaric aciduria type I (GA-I) is an inherited metabolic disease due to deficiency of glutaryl-CoA dehydrogenase (GCDH). Cognitive functions are generally thought to be spared, but have not yet been studied in detail.

Methods

Thirty patients detected by newborn screening (n = 13), high-risk screening (n = 3) or targeted metabolic testing (n = 14) were studied for simple reaction time (SRT), continuous performance (CP), visual working memory (VWM), visual-motor coordination (Tracking) and visual search (VS). Dystonia (n = 13 patients) was categorized using the Barry-Albright-Dystonia Scale (BADS). Patients were compared with 196 healthy controls. Developmental functions of cognitive performances were analysed using a negative exponential function model.

Results

BADS scores correlated with speed tests but not with tests measuring stability or higher cognitive functions without time constraints. Developmental functions of GA-I patients significantly differed from controls for SRT and VS but not for VWM and showed obvious trends for CP and Tracking. Dystonic patients were slower in SRT and CP but reached their asymptote of performance similar to asymptomatic patients and controls in all tests. Asymptomatic patients did not differ from controls, except showing significantly better results in Tracking and a trend for slower reactions in visual search. Data across all age groups of patients and controls fitted well to a model of negative exponential development.

Conclusions

Dystonic patients predominantly showed motor speed impairment, whereas performance improved with higher cognitive load. Patients without motor symptoms did not differ from controls. Developmental functions of cognitive performances were similar in patients and controls. Performance in tests with higher cognitive demand might be preserved in GA-I, even in patients with striatal degeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-015-0379-6) contains supplementary material, which is available to authorized users.

The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 1: the initial presentation

BACKGROUND

The clinical presentation of patients with organic acidurias (OAD) and urea cycle disorders (UCD) is variable; symptoms are often non-specific.

AIMS/METHODS

To improve the knowledge about OAD and UCD the E-IMD consortium established a web-based patient registry.

RESULTS

We registered 795 patients with OAD (n = 452) and UCD (n = 343), with ornithine transcarbamylase (OTC) deficiency (n = 196), glutaric aciduria type 1 (GA1; n = 150) and methylmalonic aciduria (MMA; n = 149) being the most frequent diseases. Overall, 548 patients (69 %) were symptomatic. The majority of them (n = 463) presented with acute metabolic crisis during (n = 220) or after the newborn period (n = 243) frequently demonstrating impaired consciousness, vomiting and/or muscular hypotonia. Neonatal onset of symptoms was most frequent in argininosuccinic synthetase and lyase deficiency and carbamylphosphate 1 synthetase deficiency, unexpectedly low in male OTC deficiency, and least frequently in GA1 and female OTC deficiency. For patients with MMA, propionic aciduria (PA) and OTC deficiency (male and female), hyperammonemia was more severe in metabolic crises during than after the newborn period, whereas metabolic acidosis tended to be more severe in MMA and PA patients with late onset of symptoms. Symptomatic patients without metabolic crises (n = 94) often presented with a movement disorder, mental retardation, epilepsy and psychiatric disorders (the latter in UCD only).

CONCLUSIONS

The initial presentation varies widely in OAD and UCD patients. This is a challenge for rapid diagnosis and early start of treatment. Patients with a sepsis-like neonatal crisis and those with late-onset of symptoms are both at risk of delayed or missed diagnosis.

The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 2: the evolving clinical phenotype

BACKGROUND

The disease course and long-term outcome of patients with organic acidurias (OAD) and urea cycle disorders (UCD) are incompletely understood.

AIMS

To evaluate the complex clinical phenotype of OAD and UCD patients at different ages.

RESULTS

Acquired microcephaly and movement disorders were common in OAD and UCD highlighting that the brain is the major organ involved in these diseases. Cardiomyopathy [methylmalonic (MMA) and propionic aciduria (PA)], prolonged QTc interval (PA), optic nerve atrophy [MMA, isovaleric aciduria (IVA)], pancytopenia (PA), and macrocephaly [glutaric aciduria type 1 (GA1)] were exclusively found in OAD patients, whereas hepatic involvement was more frequent in UCD patients, in particular in argininosuccinate lyase (ASL) deficiency. Chronic renal failure was often found in MMA, with highest frequency in mut(0) patients. Unexpectedly, chronic renal failure was also observed in adolescent and adult patients with GA1 and ASL deficiency. It had a similar frequency in patients with or without a movement disorder suggesting different pathophysiology. Thirteen patients (classic OAD: 3, UCD: 10) died during the study interval, ten of them during the initial metabolic crisis in the newborn period. Male patients with late-onset ornithine transcarbamylase deficiency were presumably overrepresented in the study population.

CONCLUSIONS

Neurologic impairment is common in OAD and UCD, whereas the involvement of other organs (heart, liver, kidneys, eyes) follows a disease-specific pattern. The identification of unexpected chronic renal failure in GA1 and ASL deficiency emphasizes the importance of a systematic follow-up in patients with rare diseases.

Experimental evidence that overexpression of NR2B glutamate receptor subunit is associated with brain vacuolation in adult glutaryl-CoA dehydrogenase deficient mice: A potential role for glutamatergic-induced excitotoxicity in GA I neuropathology

Glutaric aciduria type I (GA I) is biochemically characterized by accumulation of glutaric and 3-hydroxyglutaric acids in body fluids and tissues, particularly in the brain. Affected patients show progressive cortical leukoencephalopathy and chronic degeneration of the basal ganglia whose pathogenesis is still unclear. In the present work we investigated parameters of bioenergetics and redox homeostasis in various cerebral structures (cerebral cortex, striatum and hippocampus) and heart of adult wild type (Gcdh(+/+)) and glutaryl-CoA dehydrogenase deficient knockout (Gcdh(-/-)) mice fed a baseline chow. Oxidative stress parameters were also measured after acute lysine overload. Finally, mRNA expression of NMDA subunits and GLT1 transporter was determined in cerebral cortex and striatum of these animals fed a baseline or high lysine (4.7%) chow. No significant alterations of bioenergetics or redox status were observed in these mice. In contrast, mRNA expression of the NR2B glutamate receptor subunit and of the GLT1 glutamate transporter was higher in cerebral cortex of Gcdh(-/-) mice. Furthermore, NR2B expression was markedly elevated in striatum of Gcdh(-/-) animals receiving chronic Lys overload. These data indicate higher susceptibility of Gcdh(-/-) mice to excitotoxic damage, implying that this pathomechanism may contribute to the cortical and striatum alterations observed in GA I patients.

Glutaric aciduria type 1: neuroimaging features with clinical correlation

BACKGROUND

Glutaric aciduria type 1 is a rare neurometabolic disease with high morbidity.

OBJECTIVE

To describe the MR imaging abnormalities in glutaric aciduria type 1 and to identify any association between the clinical and imaging features.

MATERIALS AND METHODS

MRI scans of 29 children (mean age: 16.9 months) with confirmed diagnosis of glutaric aciduria type 1 were retrospectively reviewed. Gray matter and white matter scores were calculated based on a previously published pattern-recognition approach of assessing leukoencephalopathies. Hippocampal formation and opercular topography were assessed in relation to the known embryological basis. MRI scores were correlated with morbidity score.

RESULTS

The most consistent MRI abnormality was widened operculum with dilatation of the subarachnoid spaces surrounding underdeveloped frontotemporal lobes. Incomplete hippocampal inversion was also seen. The globus pallidus was the most frequently involved gray matter structure (86%). In addition to the central tegmental tract, white matter abnormalities preferentially involved the central and periventricular regions. The morbidity score correlated with the gray matter abnormality score (P = 0.004). Patients with dystonia had higher gray matter and morbidity scores.

CONCLUSION

Morbidity is significantly correlated with abnormality of gray matter, rather than white matter, whether secondary to acute encephalopathic crisis or insidious onset disease.

(1)H-MRS in glutaric aciduria type 1: impact of biochemical phenotype and age on the cerebral accumulation of neurotoxic metabolites

BACKGROUND

In glutaric aciduria type 1 (GA1) the neurotoxic metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OH-GA) accumulate within the brain. Due to limited efflux across the blood-brain-barrier biochemical monitoring of intracerebrally accumulating toxic metabolites is as yet not possible.

AIMS

To investigate brain metabolic patterns in glutaric aciduria type 1 using (1)H magnetic resonance spectroscopy ((1)H-MRS) with focus on detecting the disease-related neurotoxic metabolites GA and 3-OH-GA.

PATIENTS AND METHODS

Short echo time (1)H-MRS was performed in 13 treated metabolically stable patients. Twenty-one white matter and 16 basal ganglia spectra from 12 patients (age range 7 months - 22 years) were included. Subgroups based on age, biochemical phenotype and/or associated MRI changes were compared with control spectra.

RESULTS

GA was elevated in white matter of patients. 3-OH-GA was elevated in white matter of older patients with associated signal changes on MRI, which was structurally characterized by decreased creatine and phosphocreatine (tCr) and elevated choline (Cho). Metabolite changes differed with biochemical phenotype and disease duration: Low excretors with up to 30% residual enzyme activity had only mildly, non-significantly elevated GA and mildly subnormal N-acetylaspartate (tNAA). High excretors with complete lack of enzyme activity had significantly increased GA, tNAA was mildly subnormal in younger and decreased in older high excretors.

CONCLUSIONS

GA and 3-OH-GA are detectable by in vivo (1)H-MRS, which might finally allow biochemical follow-up monitoring of intracerebrally accumulating neurotoxic metabolites in GA1. A high excreting phenotype appears to be a risk factor for cerebral GA accumulation and progressive neuroaxonal compromise despite a similar clinical course in younger high and low excreting patients. This might have consequences for long-term outcome.

Adult-onset glutaric aciduria type I presenting with white matter abnormalities and subependymal nodules

A 55-year-old female presented with a 6-year history of paresthesias, incontinence, spasticity, and gait abnormalities. Neuroimaging revealed white matter abnormalities associated with subependymal nodules. Biochemical evaluation noted increased serum C5-DC glutarylcarnitines and urine glutaric and 3-hydroxyglutaric acids. Evaluation of the glutaryl-CoA dehydrogenase (GCDH) gene revealed compound heterozygosity consisting of a novel variant (c.1219C>G; p.Leu407Val) and pathogenic mutation (c.848delT; p.L283fs). Together, these results were consistent with a diagnosis of adult-onset type I glutaric aciduria.

Mitochondrial Citrate Transporter-dependent Metabolic Signature in the 22q11.2 Deletion Syndrome

The congenital disorder 22q11.2 deletion syndrome (22qDS), characterized by a hemizygous deletion of 1.5-3 Mb on chromosome 22 at locus 11.2, is the most common microdeletion disorder (estimated prevalence of 1 in 4000) and the second risk factor for schizophrenia. Nine of ∼30 genes involved in 22qDS have the potential of disrupting mitochondrial metabolism (COMT, UFD1L, DGCR8, MRPL40, PRODH, SLC25A1, TXNRD2, T10, and ZDHHC8). Deficits in bioenergetics during early postnatal brain development could set the basis for a disrupted neuronal metabolism or synaptic signaling, partly explaining the higher incidence in developmental and behavioral deficits in these individuals. Here, we investigated whether mitochondrial outcomes and metabolites from 22qDS children segregated with the altered dosage of one or several of these mitochondrial genes contributing to 22qDS etiology and/or morbidity. Plasma metabolomics, lymphocytic mitochondrial outcomes, and epigenetics (histone H3 Lys-4 trimethylation and 5-methylcytosine) were evaluated in samples from 11 22qDS children and 13 age- and sex-matched neurotypically developing controls. Metabolite differences between 22qDS children and controls reflected a shift from oxidative phosphorylation to glycolysis (higher lactate/pyruvate ratios) accompanied by an increase in reductive carboxylation of α-ketoglutarate (increased concentrations of 2-hydroxyglutaric acid, cholesterol, and fatty acids). Altered metabolism in 22qDS reflected a critical role for the haploinsufficiency of the mitochondrial citrate transporter SLC25A1, further enhanced by HIF-1α, MYC, and metabolite controls. This comprehensive profiling served to clarify the biochemistry of this disease underlying its broad, complex phenotype.

Severe Acute Subdural Hemorrhage in a Patient With Glutaric Aciduria Type I After Minor Head Trauma: A Case Report

Glutaric aciduria type I is a rare metabolic disorder caused by deficiency of glutaryl-coenzyme A dehydrogenase. Chronic subdural hematomas have been reported in glutaric aciduria type I and are considered as important differential diagnosis of nonaccidental head trauma. However, chronic subdural hematomas are usually thought to remain clinically silent in these patients. Here we report on a hitherto asymptomatic glutaric aciduria type I patient who developed severe, acute subdural hemorrhage after minor accidental head injury at age 23 months. Computed tomography confirmed significant mass effect on the brain necessitating decompressive hemicraniectomy. Subdural hemorrhage caused large hypoxic lesions of the cerebral cortex and subcortical regions resulting in spastic tetraplegia, dystonia, and loss of developmental milestones. This report emphasizes that acute subdural hemorrhage may be a life-threatening complication in glutaric aciduria type I patients after minor head trauma and should be considered in those patients presenting with neurologic deterioration after accidental head injury.

Glutaric Acidemia Type 1-Clinico-Molecular Profile and Novel Mutations in GCDH Gene in Indian Patients

Glutaric acidemia I (GA I, #231670) is one of the treatable, autosomal recessively inherited metabolic disorders. Macrocephaly, acute encephalitis-like crises, dystonia and characteristic frontotemporal atrophy are the hallmarks of this disease. In this communication, we present the clinical, biochemical and molecular profile of seventeen GA I patients from 15 unrelated families from India and report seven novel mutations in GCDH gene (c.281G>A (p.Arg94Gln), c.401A>G (p.Asp134Gly), c.662T>C (p.Leu221Pro), c.881G>C (p.Arg294Pro), c.1173dupG (p.Asn392Glufs*5), c.1238A>G (p.Tyr413Cys) and c.1241A>C (p.Glu414Ala)). Out of these, c.662T>C (p.Leu221Pro) in exon 8 and c.281G>A (p.Arg94Gln) allele in exon 4 were low excretor alleles, whereas c.1241A>C (p.Glu414Ala), c.1173dupG and c.1207C>T (p.His403Tyr) in exon 11 were high excretor alleles. We conclude that c.1204C>T (p.Arg402Trp) is probably the most common mutant allele. Exons 11 and 8 are the hot spot regions of GCDH gene in Indian patients with GA I. An early diagnosis and timely intervention can improve the underlying prognosis. Molecular confirmation is helpful in providing genetic counselling and prenatal diagnosis in subsequent pregnancy.

The aetiology of neonatal seizures and the diagnostic contribution of neonatal cerebral magnetic resonance imaging

AIM

The aim of this study was to delineate aetiologies and explore the diagnostic value of cerebral magnetic resonance imaging (MRI) in addition to cranial ultrasonography (cUS) in infants presenting with neonatal seizures.

METHOD

This retrospective cohort study comprised infants (gestational age 35.0-42.6wks) with seizures, confirmed by either continuous amplitude-integrated electroencephalography (aEEG) or standard EEG and admitted during a 14-year period to a level three neonatal intensive care unit (n=378; 216 males, 162 females; mean [SD] birthweight 3334g [594]). All infants underwent cUS and MRI (MRI on median of 5 days after birth, range 0-58d) within the first admission period.

RESULTS

An underlying aetiology was identified in 354 infants (93.7%). The most common aetiologies identified were hypoxic-ischaemic encephalopathy (46%), intracranial haemorrhage (12.2%), and perinatal arterial ischaemic stroke (10.6%). When comparing MRI with cUS in these 354 infants MRI showed new findings which did not become apparent on cUS, contributing to a diagnosis in 42 (11.9%) infants and providing additional information to cUS, contributing to a diagnosis in 141 (39.8%). cUS alone would have allowed a diagnosis in only 37.9% of infants (134/354).

INTERPRETATION

Cerebral MRI contributed to making a diagnosis in the majority of infants. In 11.9% of infants the diagnosis would have been missed if only cUS were used and cerebral MRI added significantly to the information obtained in 39.8% of infants. These data suggest that cerebral MRI should be performed in all newborn infants presenting with EEG- or aEEG-confirmed seizures.

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.

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).

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.

Increased blood-brain barrier permeability and alterations in perivascular astrocytes and pericytes induced by intracisternal glutaric acid

Background

Glutaric acid (GA) is a dicarboxylic acid that accumulates in millimolar concentrations in glutaric acidemia I (GA-I), an inherited neurometabolic childhood disease characterized by extensive neurodegeneration. Vascular dysfunction is a common and early pathological feature in GA-I, although the underlying mechanisms remain unknown. In the present study, we have used a previously-validated rat model of GA-I to determine the effect of GA on the blood- brain barrier (BBB) and the neurovascular unit.

Methods

Newborn rat pups received a single injection of GA (1 μmol/g) or vehicle into the cisterna magna. BBB permeability was analyzed at 14 and 30 days post injection (DPI) by assessing Evans blue (EB) and immunoglobulin G (IgG) extravasation. Blood vessels and microglia were labeled with tomato lectin. Characterization of EB positive cells was made by double labeling with antibodies to astrocyte and neuronal markers. Immunohistochemistry against aquaporin 4 (AQP4), β receptor of the platelet derived growth factor (PDGFRβ) and laminin was used to recognize astrocyte endfeet, pericytes and basal lamina. Zonula occludens 1 (ZO-1) and occludin striatal expression was assessed by Western blotting.

Results

Perinatal intracisternal GA administration caused an increased extravasation of free EB, but not of IgG, into the striatal parenchyma at 14 and 30 DPI. EB extravasated through the BBB was internalized exclusively into neurons. GA-injected animals did not show significant changes in the area of small blood vessels in the striatum, but at 30 DPI there was a significant decrease in AQP4, PDGFRβ and laminin positive areas associated with small blood vessels. Occludin and ZO-1 expression in the striatal tissue was unchanged in all conditions analyzed.

Conclusions

The present study shows a previously-unknown effect of a perinatal administration of a single intracisternal GA injection on BBB permeability and on key components of the neurovascular unit. The results suggest BBB leakage is a pathogenic mechanism and a potential therapeutic target for patients with GA-I.

Increased glutamate receptor and transporter expression in the cerebral cortex and striatum of gcdh-/- mice: possible implications for the neuropathology of glutaric acidemia type I

We determined mRNA expression of the ionotropic glutamate receptors NMDA (NR1, NR2A and NR2B subunits), AMPA (GluR2 subunit) and kainate (GluR6 subunit), as well as of the glutamate transporters GLAST and GLT1 in cerebral cortex and striatum of wild type (WT) and glutaryl-CoA dehydrogenase deficient (Gchh^-/-) mice aged 7, 30 and 60 days. The protein expression levels of some of these membrane proteins were also measured. Overexpression of NR2A and NR2B in striatum and of GluR2 and GluR6 in cerebral cortex was observed in 7-day-old Gcdh^-/-. There was also an increase of mRNA expression of all NMDA subunits in cerebral cortex and of NR2A and NR2B in striatum of 30-day-old Gcdh^-/- mice. At 60 days of life, all ionotropic receptors were overexpressed in cerebral cortex and striatum of Gcdh^-/- mice. Higher expression of GLAST and GLT1 transporters was also verified in cerebral cortex and striatum of Gcdh^-/- mice aged 30 and 60 days, whereas at 7 days of life GLAST was overexpressed only in striatum from this mutant mice. Furthermore, high lysine intake induced mRNA overexpression of NR2A, NR2B and GLAST transcripts in striatum, as well as of GluR2 and GluR6 in both striatum and cerebral cortex of Gcdh^-/- mice. Finally, we found that the protein expression of NR2A, NR2B, GLT1 and GLAST were significantly greater in cerebral cortex of Gcdh^-/- mice, whereas NR2B and GLT1 was similarly enhanced in striatum, implying that these transcripts were translated into their products. These results provide evidence that glutamate receptor and transporter expression is higher in Gcdh^-/- mice and that these alterations may be involved in the pathophysiology of GA I and possibly explain, at least in part, the vulnerability of striatum and cerebral cortex to injury in patients affected by GA I.

Mechanism of metabolic stroke and spontaneous cerebral hemorrhage in glutaric aciduria type I

Background

Metabolic stroke is the rapid onset of lasting central neurological deficit associated with decompensation of an underlying metabolic disorder. Glutaric aciduria type I (GA1) is an inherited disorder of lysine and tryptophan metabolism presenting with metabolic stroke in infancy. The clinical presentation includes bilateral striatal necrosis and spontaneous subdural and retinal hemorrhages, which has been frequently misdiagnosed as non-accidental head trauma. The mechanisms underlying metabolic stroke and spontaneous hemorrhage are poorly understood.

Results

Using a mouse model of GA1, we show that metabolic stroke progresses in the opposite sequence of ischemic stroke, with initial neuronal swelling and vacuole formation leading to cerebral capillary occlusion. Focal regions of cortical followed by striatal capillaries are occluded with shunting to larger non-exchange vessels leading to early filling and dilation of deep cerebral veins. Blood–brain barrier breakdown was associated with displacement of tight-junction protein Occludin.

Conclusion

Together the current findings illuminate the pathophysiology of metabolic stroke and vascular compromise in GA1, which may translate to other neurometabolic disorders presenting with stroke.

HIBCH mutations can cause Leigh-like disease with combined deficiency of multiple mitochondrial respiratory chain enzymes and pyruvate dehydrogenase

Background

Deficiency of 3-hydroxy-isobutyryl-CoA hydrolase (HIBCH) caused by HIBCH mutations is a rare cerebral organic aciduria caused by disturbance of valine catabolism. Multiple mitochondrial respiratory chain (RC) enzyme deficiencies can arise from a number of mechanisms, including defective maintenance or expression of mitochondrial DNA. Impaired biosynthesis of iron-sulphur clusters and lipoic acid can lead to pyruvate dehydrogenase complex (PDHc) deficiency in addition to multiple RC deficiencies, known as the multiple mitochondrial dysfunctions syndrome.

Methods

Two brothers born to distantly related Pakistani parents presenting in early infancy with a progressive neurodegenerative disorder, associated with basal ganglia changes on brain magnetic resonance imaging, were investigated for suspected Leigh-like mitochondrial disease. The index case had deficiencies of multiple RC enzymes and PDHc in skeletal muscle and fibroblasts respectively, but these were normal in his younger brother. The observation of persistently elevated hydroxy-C4-carnitine levels in the younger brother led to suspicion of HIBCH deficiency, which was investigated by biochemical assay in cultured skin fibroblasts and molecular genetic analysis.

Results

Specific spectrophotometric enzyme assay revealed HIBCH activity to be below detectable limits in cultured skin fibroblasts from both brothers. Direct Sanger sequence analysis demonstrated a novel homozygous pathogenic missense mutation c.950G <A; p.Gly317Glu in the HIBCH gene, which segregated with infantile-onset neurodegeneration within the family.

Conclusions

HIBCH deficiency, a disorder of valine catabolism, is a novel cause of the multiple mitochondrial dysfunctions syndrome, and should be considered in the differential diagnosis of patients presenting with multiple RC deficiencies and/or pyruvate dehydrogenase deficiency.

N-acetylcysteine prevents spatial memory impairment induced by chronic early postnatal glutaric acid and lipopolysaccharide in rat pups

Background and Aims

Glutaric aciduria type I (GA-I) is characterized by accumulation of glutaric acid (GA) and neurological symptoms, such as cognitive impairment. Although this disease is related to oxidative stress and inflammation, it is not known whether these processes facilitate the memory impairment. Our objective was to investigate the performance of rat pups chronically injected with GA and lipopolysaccharide (LPS) in spatial memory test, antioxidant defenses, cytokines levels, Na+, K+-ATPase activity, and hippocampal volume. We also evaluated the effect of N-acetylcysteine (NAC) on theses markers.

Methods

Rat pups were injected with GA (5umol g of body weight-1, subcutaneously; twice per day; from 5th to 28th day of life), and were supplemented with NAC (150mg/kg/day; intragastric gavage; for the same period). LPS (2mg/kg; E.coli 055 B5) or vehicle (saline 0.9%) was injected intraperitoneally, once per day, from 25th to 28th day of life. Oxidative stress and inflammatory biomarkers as well as hippocampal volume were assessed.

Results

GA caused spatial learning deficit in the Barnes maze and LPS potentiated this effect. GA and LPS increased TNF-α and IL-1β levels. The co-administration of these compounds potentiated the increase of IL-1β levels but not TNF-α levels in the hippocampus. GA and LPS increased TBARS (thiobarbituric acid-reactive substance) content, reduced antioxidant defenses and inhibited Na+, K+-ATPase activity. GA and LPS co-administration did not have additive effect on oxidative stress markers and Na+, K+ pump. The hippocampal volume did not change after GA or LPS administration. NAC protected against impairment of spatial learning and increase of cytokines levels. NAC Also protected against inhibition of Na+,K+-ATPase activity and oxidative markers.

Conclusions

These results suggest that inflammatory and oxidative markers may underlie at least in part of the neuropathology of GA-I in this model. Thus, NAC could represent a possible adjuvant therapy in treatment of children with GA-I.

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.

Current concepts in organic acidurias: understanding intra- and extracerebral disease manifestation

This review focuses on the pathophysiology of organic acidurias (OADs), in particular, OADs caused by deficient amino acid metabolism. OADs are termed classical if patients present with acute metabolic decompensation and multiorgan dysfunction or cerebral if patients predominantly present with neurological symptoms but without metabolic crises. In both groups, however, the brain is the major target. The high energy demand of the brain, the gate-keeping function of the blood-brain barrier, a high lipid content, vulnerable neuronal subpopulations, and glutamatergic neurotransmission all make the brain particularly vulnerable against mitochondrial dysfunction, oxidative stress, and excitotoxicity. In fact, toxic metabolites in OADs are thought to cause secondary impairment of energy metabolism; some of these toxic metabolites are trapped in the brain. In contrast to cerebral OADs, patients with classical OADs have an increased risk of multiorgan dysfunction. The lack of the anaplerotic propionate pathway, synergistic inhibition of energy metabolism by toxic metabolites, and multiple oxidative phosphorylation (OXPHOS) deficiency may best explain the involvement of organs with a high energy demand. Intriguingly, late-onset organ dysfunction may manifest even under metabolically stable conditions. This might be explained by chronic mitochondrial DNA depletion, increased production of reactive oxygen species, and altered gene expression due to histone modification. In conclusion, pathomechanisms underlying the acute disease manifestation in OADs, with a particular focus on the brain, are partially understood. More work is required to predict the risk and to elucidate the mechanism of late-onset organ dysfunction, extracerebral disease manifestation, and tumorigenesis.

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.

MR differential diagnosis of acute deep grey matter pathology in paediatric patients

A high metabolic demand, rich vascularization and high concentrations of ionic elements leading to the generation of oxygen free radicals, give to the deep grey matter (DGM) nuclei specific susceptibility to both acute and chronic insults, especially in paediatric patients. Reaching a diagnosis in the early stages of acute diseases in many patients is crucial for instigating prompt specific therapy leading to a favourable outcome. On the basis of a review of a 10-year in-house database and a review of the literature on CNS pathology involving the DGM nuclei in paediatric patients, we summarize the MR findings and clinical clues that may help the radiologist in the difficult differential diagnosis process. The terms "acute" and "chronic" refer to the clinical onset of the disease. MR imaging allows the detection of an injury, determination of its precise anatomical location and characterization of the signal changes. This, combined with a knowledge of specific MRI patterns, may be a roadmap to a definite diagnosis. Clinical history, physical and laboratory findings, timing of the MR examination and advanced MR imaging techniques (diffusion-weighted imaging and (1)H-MR spectroscopy), are crucial in some patients.

Brain MRI findings as an important diagnostic clue in glutaric aciduria type 1

Glutaric aciduria type 1 is an autosomal recessive disorder caused by deficiency of glutaryl-coenzyme A dehydrogenase, with accumulation of glutaric acid, 3-hydroxyglutaric acid and glutaconic acid. Increased blood glutarylcarnitine levels are the basis for identification of affected infants by newborn screening. Despite the highly variability, this disease usually presents with an acute encephalitis-like encephalopathy in infancy or childhood after a period of normal development. The characteristic neurological sequel is a complex movement disorder due to acute bilateral striatal injury. Frequently, the only abnormality preceding the first episode is a progressive macrocephaly. Although neuroimaging findings are quite variable, the widening of the Sylvian fissures combined with abnormalities of the basal ganglia in a child with macrocephaly should raise the suspicion of this diagnosis. We describe two patients in whom macrocephaly was the only presenting symptom and whose diagnosis was suggested by the brain MRI findings. Our purpose is to illustrate the clinical value of neuroimaging in the diagnosis of glutaric aciduria type 1 even before the onset of neurologic symptoms, which is particularly important if newborn screening is not available.

Effects of targeted suppression of glutaryl-CoA dehydrogenase by lentivirus-mediated shRNA and excessive intake of lysine on apoptosis in rat striatal neurons

In glutaric aciduria type 1 (GA1), glutaryl-CoA dehydrogenase (GCDH) deficiency has been shown to be responsible for the accumulation of glutaric acid and striatal degeneration. However, the mechanisms by which GA1 induces striatal degeneration remain unclear. In this study, we aimed to establish a novel neuronal model of GA1 and to investigate the effects of GCDH deficiency and lysine-related metabolites on the viability of rat striatal neurons. Thus we constructed a lentiviral vector containing short hairpin RNA targeted against the GCDH gene expression (lentivirus-shRNA) in neurons. A virus containing a scrambled short hairpin RNA construct served as a control. Addition of lysine (5 mmol/L) was used to mimic hypermetabolism. Cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Apoptosis was assessed using Hoechst33342 staining and Annexin V-PE/7-AAD staining. The mitochondrial membrane potential (MPP) was monitored using tetramethylrhodamine methyl ester. The expression levels of caspases 3, 8, and 9 were determined by Western blotting. We found that lentivirus-shRNA induced apoptosis and decreased MMP levels in neurons, and addition of 5 mmol/L lysine enhanced this effect markedly. Lentivirus-shRNA upregulated the protein levels of caspases 3 and 9 regardless of the presence of 5 mmol/L lysine. The expression level of caspase 8 was higher in neurons co-treated with lentivirus-shRNA and 5 mmol/L lysine than in control. Benzyloxy-carbonyl-Val-Ala-Asp(OMe)-fluoromethylketone, a pan-caspase inhibitor, blocked the apoptosis induced by lentivirus-shRNA and 5 mmol/L lysine to a great extent. These results indicate that the targeted suppression of GCDH by lentivirus-mediated shRNA and excessive intake of lysine may be a useful cell model of GA1. These also suggest that GA1-induced striatal degeneration is partially caspase-dependent.

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.

Promising outcomes in glutaric aciduria type I patients detected by newborn screening

Glutaric aciduria type I (GA-I) is an inborn error of lysine and tryptophan metabolism. Clinical manifestations of GA-I include dystonic or dyskinetic cerebral palsy, but when the symptoms occur, treatment is not effective. In Taiwan, newborn screening for GA-I started in 2001; we wish to evaluate the outcomes of patients detected through newborn screening. Newborns diagnosed with GA-I by abnormal dried blood spot glutarylcarnitine (C5DC) levels followed in our hospital were included in this study. They were treated with special diets, carnitine supplements, and immediate stress avoidance. Six patients were included in this study. All patients were treated prior to reaching 1 month of age. They were followed up with for 4 to 9 years. One patient had encephalopathic crisis episodes prior to turning 1 year old that caused pallidal lesions. Another patient had a chronic progressive disease during infancy that caused bilateral putamen lesions. These two patients had delayed development, but their brain lesions were resolved. The other four patients ran uneventful courses. They had normal intelligenece, ranged between average to low average level and their brain magnetic resonance imaging showed only high intensity over deep white matter. Patients with GA-I diagnosed by newborn screening have promising outcomes, though the risks of disease progression prior to 1 year of age remain significant.

Ammonium accumulation and cell death in a rat 3D brain cell model of glutaric aciduria type I

Glutaric aciduria type I (glutaryl-CoA dehydrogenase deficiency) is an inborn error of metabolism that usually manifests in infancy by an acute encephalopathic crisis and often results in permanent motor handicap. Biochemical hallmarks of this disease are elevated levels of glutarate and 3-hydroxyglutarate in blood and urine. The neuropathology of this disease is still poorly understood, as low lysine diet and carnitine supplementation do not always prevent brain damage, even in early-treated patients. We used a 3D in vitro model of rat organotypic brain cell cultures in aggregates to mimic glutaric aciduria type I by repeated administration of 1 mM glutarate or 3-hydroxyglutarate at two time points representing different developmental stages. Both metabolites were deleterious for the developing brain cells, with 3-hydroxyglutarate being the most toxic metabolite in our model. Astrocytes were the cells most strongly affected by metabolite exposure. In culture medium, we observed an up to 11-fold increase of ammonium in the culture medium with a concomitant decrease of glutamine. We further observed an increase in lactate and a concomitant decrease in glucose. Exposure to 3-hydroxyglutarate led to a significantly increased cell death rate. Thus, we propose a three step model for brain damage in glutaric aciduria type I: (i) 3-OHGA causes the death of astrocytes, (ii) deficiency of the astrocytic enzyme glutamine synthetase leads to intracerebral ammonium accumulation, and (iii) high ammonium triggers secondary death of other brain cells. These unexpected findings need to be further investigated and verified in vivo. They suggest that intracerebral ammonium accumulation might be an important target for the development of more effective treatment strategies to prevent brain damage in patients with glutaric aciduria type I.

Defects in amino acid catabolism and the urea cycle

Symptoms in patients with defects in amino acid catabolism and the urea cycle usually develop because of intoxication of accumulating metabolites. The cumulative prevalence of these disorders is considerable (at least>1:2000 newborns). Timely and correct intervention during the initial presentation and during later episodes is most important. Evaluation of metabolic parameters should be performed on an emergency basis in every patient with symptoms of unexplained metabolic crisis, intoxication, and/or unexplained encephalopathy. A substantial number of patients develop acute encephalopathy or chronic and fluctuating progressive neurological disease. The so-called cerebral organic acid disorders present with (progressive) neurological symptoms: ataxia, myoclonus, extrapyramidal symptoms, and "metabolic stroke." Important diagnostic clues, such as white matter abnormalities, cortical or cerebellar atrophy, and injury of the basal ganglia can be derived from cranial magnetic resonance imaging (MRI). Long-term neurological disease is common, particularly in untreated patients, and the manifestations are varied, the most frequent being (1) mental defect, (2) epilepsy, and (3) movement disorders. Successful treatment strategies are becoming increasingly available. They mostly require an experienced interdisciplinary team including a neuropediatrician and/or later on a neurologist.

Disruption of brain redox homeostasis in glutaryl-CoA dehydrogenase deficient mice treated with high dietary lysine supplementation

Deficiency of glutaryl-CoA dehydrogenase (GCDH) activity or glutaric aciduria type I (GA I) is an inherited neurometabolic disorder biochemically characterized by predominant accumulation of glutaric acid and 3-hydroxyglutaric acid in the brain and other tissues. Affected patients usually present acute striatum necrosis during encephalopathic crises triggered by metabolic stress situations, as well as chronic leukodystrophy and delayed myelination. Considering that the mechanisms underlying the brain injury in this disease are not yet fully established, in the present study we investigated important parameters of oxidative stress in the brain (cerebral cortex, striatum and hippocampus), liver and heart of 30-day-old GCDH deficient knockout (Gcdh(-/-)) and wild type (WT) mice submitted to a normal lysine (Lys) (0.9% Lys), or high Lys diets (2.8% or 4.7% Lys) for 60 h. It was observed that the dietary supplementation of 2.8% and 4.7% Lys elicited noticeable oxidative stress, as verified by an increase of malondialdehyde concentrations (lipid oxidative damage) and 2-7-dihydrodichlorofluorescein (DCFH) oxidation (free radical production), as well as a decrease of reduced glutathione levels and alteration of various antioxidant enzyme activities (antioxidant defenses) in the cerebral cortex and the striatum, but not in the hippocampus, the liver and the heart of Gcdh(-/-) mice, as compared to WT mice receiving the same diets. Furthermore, alterations of oxidative stress parameters in the cerebral cortex and striatum were more accentuated in symptomatic, as compared to asymptomatic Gcdh(-/-) mice exposed to 4.7% Lys overload. Histopathological studies performed in the cerebral cortex and striatum of these animals exposed to high dietary Lys revealed increased expression of oxidative stress markers despite the absence of significant structural damage. The results indicate that a disruption of redox homeostasis in the cerebral cortex and striatum of young Gcdh(-/-) mice exposed to increased Lys diet may possibly represent an important pathomechanism of brain injury in GA I patients under metabolic stress.

Progressive dystonia

Progressive dystonias are a clinically and genetically heterogeneous group of movement disorders. In the primary forms, dystonia is the only sign of the disease, and the cause is either unknown or genetic. In the secondary forms, dystonia is usually only one of several disease manifestations and the cause may be genetic or due to other insults. Monogenic defects have been found to underlie many forms of dystonia syndromes, which are designated DYT1-20. Dystonias with known genes include DYT1 and DYT6 dystonia, presenting as isolated torsion dystonia, as well as DYT5 (dopa-responsive dystonia), DYT11 (myoclonus-dystonia), and DYT12 (rapid-onset dystonia-parkinsonism), where dystonia occurs in conjunction with other types of movement disorders. All of these conditions follow an autosomal dominant mode of inheritance, usually develop in childhood or early adolescence, and show an initially progressive course with stabilization in early adulthood. In secondary dystonias, there are often atypical features and additional neurological signs, such as prominent tongue and perioral involvement, pyramidal signs, ataxia, oculomotor abnormalities, or cognitive disturbances. Acquired brain lesions typically affect the putamen, thalamus, or globus pallidus and cause contralateral hemidystonia. Dystonia can be part of the clinical syndrome in many heredodegenerative disorders, or may be drug-induced or psychogenic.