Diagnosis and management of glutaric aciduria type I

Treatment of glutaric aciduria type I (GA-I) via intracerebroventricular delivery of GCDH

Glutaric aciduria type I (GA-I) is an autosomal recessive genetic disorder caused by a deficiency in glutaryl-CoA dehydrogenase (GCDH). Patients who do not receive proper treatment may die from acute encephalopathic crisis. Current treatments for GA-I include a low-lysine diet combined with oral supplementation of L-carnitine. A mouse model of Gcdh c.422_428del/c.422_428del (Gcdh -/-) was generated in our laboratory using CRISPR/Cas9. Gcdh -/- mice had significantly higher levels of glutaric acid (GA) in the plasma, liver, and brain than those in wild-type C57BL/6 mice. When given a high-protein diet (HPD) for two days, approximately 60% of Gcdh -/- mice did not survive the metabolic stress. To evaluate whether GCDH gene replacement therapy could be used to provide sustained treatment for patients with GA-1, we prepared a recombinant adeno-associated virus (rAAV) carrying a human GCDH expression cassette and injected it into Gcdh -/- neonates for a proof-of-concept (PoC) study. Our study demonstrated that delivering rAAV to the central nervous system (CNS), but not the peripheral system, significantly increased the survival rate under HPD exposure. Our study also demonstrated that rAAVPHP.eB mediated a higher efficiency than that of rAAV9 in increasing the survival rate. Surviving mice showed dose-dependent GCDH protein expression in the CNS and downregulation of GA levels. Our study demonstrated that AAV-based gene replacement therapy was effective for GA-I treatment and provided a feasible solution for this unmet medical need.

Clinical, biochemical and molecular findings of 24 Brazilian patients with glutaric acidemia type 1: 4 novel mutations in the GCDH gene

Glutaric aciduria type 1 (GA-1) is a rare but treatable inherited disease caused by deficiency of glutaryl-CoA dehydrogenase activity due to GCDH gene mutations. In this study, we report 24 symptomatic GA-1 Brazilian patients, and present their clinical, biochemical, and molecular findings. Patients were diagnosed by high levels of glutaric and/or 3-hydroxyglutaric and glutarylcarnitine. Diagnosis was confirmed by genetic analysis. Most patients had the early-onset severe form of the disease and the main features were neurological deterioration, seizures and dystonia, usually following an episode of metabolic decompensation. Despite the early symptomatology, diagnosis took a long time for most patients. We identified 13 variants in the GCDH gene, four of them were novel: c.91 + 5G > A, c.167T > G, c.257C > T, and c.10A > T. The most common mutation was c.1204C > T (p.R402W). Surprisingly, the second most frequent mutation was the new mutation c.91 + 5G > A (IVS1 ds G-A + 5). Our results allowed a complete characterization of the GA-1 Brazilian patients. Besides, they expand the mutational spectrum of GA-1, with the description of four new mutations. This work reinforces the importance of awareness of GA-1 among doctors in order to allow early diagnosis and treatment in countries like Brazil where the disease has not been included in newborn screening programs.

Cerebral palsy: Aetiology, pathophysiology and therapeutic interventions

Cerebral palsy (CP) is the most common non-progressive neurodevelopmental disorder in which the impairment of motor and posture functions occurs. This condition may be present in many different clinical spectra. Various aetiological and risk factors play a crucial role in the causation of CP. In various cases, the causes of CP may not be apparent. Interruption in the supply of oxygen to the fetus or brain asphyxia was considered to be the main causative factor explaining CP. Antenatal, perinatal, and postnatal factors could be involved in the origin of CP. Understanding its pathophysiology is also crucial for developing preventive and protective strategies. A major advancement in the brain stimulation techniques has emerged as a promising status in diagnostic and interventional approaches. This review provides a brief explanation about the various aetiological factors, pathophysiology, and recent therapeutic approaches in the treatment of cerebral palsy.

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

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

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

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

Formation of 3-hydroxyglutaric acid in glutaric aciduria type I: in vitro participation of medium chain acyl-CoA dehydrogenase

3-Hydroxyglutaric acid (3-OH-GA) in urine has been identified as the most reliable diagnostic marker for glutaric aciduria type I (GA I). We showed that hydratation of glutaconyl-CoA to 3-hydroxyglutaryl-CoA, which is subsequently hydrolyzed to 3-OH-GA, is efficiently catalyzed by 3-methylglutaconyl-CoA hydratase (3-MGH). We have now investigated whether mitochondrial acyl-CoA-dehydrogenases can convert glutaryl-CoA to glutaconyl-CoA. Short-chain acyl-CoA dehydrogenase (SCAD), medium-chain acyl-CoA dehydrogenase (MCAD), and long-chain acyl-CoA dehydrogenase (LCAD) accepted glutaryl-CoA as a substrate. The highest k cat of glutaryl-CoA was found for MCAD (0.12 ± 0.01 second-1) and was about 26-fold and 52-fold higher than those of LCAD and SCAD, respectively. The turnover of MCAD for glutaryl-CoA was about 1.5% of that of its natural substrate octanoyl-CoA. Despite high K m (above 600 μM) and low turnover rate, the oxidation of glutaryl-CoA by MCAD in combination with 3-MGH could explain the urinary concentration of 3-OH-GA in GA I patients.

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.

Genetic Screening of Selected Disease-Causing Mutations in Glutaryl-CoA Dehydrogenase Gene among Indian Patients with Glutaric Aciduria Type I

Glutaric aciduria type I (GA-I) is an organic aciduria caused by glutaryl-CoA dehydrogenase (GCDH) deficiency. There are limited studies on GA-I from India. A total of 48 Indian GA-I patients were screened for selected disease-causing mutations such as R402W, A421V, A293T, R227P, and V400M using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Among these patients, 9 (18.8%) had R402W mutation, and none had A421V, A293T, R227P, or V400M mutation. One low excretor mutation (P286S) and several novel mutations (I152M, Q144P, and E414X) were also found in this study. We conclude that among selected mutations, R402W is the most common mutation found among Indian GA-I patients.

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.”

Severe neurological manifestations in an Egyptian patient with a novel frameshift mutation in the Glutaryl-CoA dehydrogenase gene

To characterize an Egyptian patient with glutaric acidemia type I (GA I) and to identify the causative mutation(s) that may be responsible for the disease phenotype. MRI was performed on the patient using the 1.5 T magnet, biochemical analysis was carried out using gas chromatography/mass spectrometry on the patient's dried blood spot, and the patient's organic acids were measured in dried blood and a urine sample using MS/MS and GC/MS, respectively. Total RNA was isolated from the patient's peripheral blood, and the synthesized cDNA was bi-directionally sequenced. The patient exhibited clinical features and MRI findings compatible with a diagnosis of GA I. The abnormal elevation of organic acids in the urine supported the presence of glutaryl-CoA dehydrogenase deficiency. Gene sequencing revealed a novel homozygous frameshift mutation, c.644_645insCTCG; p.(Pro217Leufs*14), in exon 8 of the GCDH gene. The present study revealed a novel frameshift mutation responsible for a severe GA I phenotype in an Egyptian patient. This novel mutation will ultimately contribute to a better understanding of the molecular pathology of the disease and shed light on the intricacies of the genotype-phenotype correlation of GA I disease.

Kinetic and molecular orbital analyses of dicarboxylic acylcarnitine methylesterification show that derivatization may affect the screening of newborns by tandem mass spectrometry

Newborns are routinely screened for organic acidemias by acylcarnitine analysis. We previously reported the partial catalytic methylesterification of dicarboxylic acylcarnitines by benzenesulfonic acid moiety in the solid extraction cartridge during extraction from serum. Since the diagnosis of organic acidemias by tandem mass spectrometry is affected by the higher molecular weight of these derivatized acylcarnitines, we investigated the methylesterification conditions. The kinetic constants for the methylesterification of carboxyl groups on the acyl and carnitine sides of carnitine were 2.5 and 0.24h(-1), respectively. The physical basis underlying this difference in methylesterification rates was clarified theoretically, illustrating that methylesterification during extraction proceeds easily and must be prevented.

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.

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.

A treatable neurometabolic disorder: glutaric aciduria type 1

Glutaric aciduria type 1 (GA-1) is an autosomal recessive disorder of lysine, hydroxylysine, and tryptophan metabolism caused by deficiency of glutaryl-CoA dehydrogenase. It results in the accumulation of 3-hydroxyglutaric and glutaric acid. Affected patients can present with brain atrophy and macrocephaly and with acute dystonia secondary to striatal degeneration in most cases triggered by an intercurrent childhood infection with fever between 6 and 18 months of age. We report two such cases with macrocephaly, typical MRI pictures, and tandem mass spectrometry suggestive of glutaric aciduria type 1.

Cyclic vomiting syndrome masking a fatal metabolic disease

Disorders of fatty acid oxidation are rare but can be fatal. Hypoglycaemia with acidosis is a cardinal feature. Cases may present during early childhood or can be delayed into adolescence or beyond. We present a case of multiple acyl-coenzyme A dehydrogenase deficiency (MADD), an extremely rare disorder of fatty acid oxidation. Our 20-year-old patient presented with cardiovascular collapse, raised anion gap metabolic acidosis and non-ketotic hypoglycaemia. She subsequently developed multi-organ failure and sadly died. She had a previous diagnosis of cyclic vomiting syndrome (CVS) for more than 10 years, warranting frequent hospital admissions. The association between CVS and MADD has been made before though the exact relationship is unclear. All patients with persistent severe CVS should have metabolic investigations to exclude disorders of fatty acid oxidation. In case of non-ketotic hypoglycaemia with acidosis, the patient should be urgently referred to a specialist in metabolic diseases. All practitioners should be aware of these rare disorders as a cause of unexplained acidosis.

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.

The unsolved puzzle of neuropathogenesis in glutaric aciduria type I

Glutaric aciduria type I (GA-I) is a cerebral organic aciduria caused by deficiency of glutaryl-Co-A dehydrogenase (GCDH). GCDH deficiency leads to accumulation of glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA), two metabolites that are believed to be neurotoxic, in brain and body fluids. The disorder usually becomes clinically manifest during a catabolic state (e.g. intercurrent illness) with an acute encephalopathic crisis that results in striatal necrosis and in a permanent dystonic-dyskinetic movement disorder. The results of numerous in vitro and in vivo studies have pointed to three main mechanisms involved in the metabolite-mediated neuronal damage: excitotoxicity, impairment of energy metabolism and oxidative stress. There is evidence that during a metabolic crisis GA and its metabolites are produced endogenously in the CNS and accumulate because of limiting transport mechanisms across the blood-brain barrier. Despite extensive experimental work, the relative contribution of the proposed pathogenic mechanisms remains unclear and specific therapeutic approaches have yet to be developed. Here, we review the experimental evidence and try to delineate possible pathogenetic models and approaches for future studies.

Safety, efficacy and physiological actions of a lysine-free, arginine-rich formula to treat glutaryl-CoA dehydrogenase deficiency: focus on cerebral amino acid influx

Striatal degeneration from glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type 1, GA1) is associated with cerebral formation and entrapment of glutaryl-CoA and its derivatives that depend on cerebral lysine influx. In 2006 we designed a lysine-free study formula enriched with arginine to selectively block lysine transport across cerebral endothelia and thereby limit glutaryl-CoA production by brain. Between 2006 and present, we treated twelve consecutive children with study formula (LYSx group) while holding all other treatment practices constant. Clinical and biochemical outcomes were compared to 25 GA1 patients (PROx group) treated between 1995 and 2005 with natural protein restriction (dietary lysine/arginine ratio of 1.7±0.3 mg:mg). We used published kinetic parameters of the y+and LAT1 blood-brain barrier transporters to model the influx of amino acids into the brain. Arginine fortification to achieve a mean dietary lysine/arginine ratio of 0.7±0.2 mg:mg was neuroprotective. All 12 LYSx patients are physically and neurologically healthy after 28 aggregate patient-years of follow up (current ages 28±21 months) and there were no adverse events related to formula use. This represents a 36% reduction of neurological risk (95% confidence interval 14-52%, p=0.018) that we can directly attribute to altered amino acid intake. During the first year of life, 20% lower lysine intake and two-fold higher arginine intake by LYSx patients were associated with 50% lower plasma lysine, 3-fold lower plasma lysine/arginine concentration ratio, 42% lower mean calculated cerebral lysine influx, 54% higher calculated cerebral arginine influx, 15-26% higher calculated cerebral influx of several anaplerotic precursors (isoleucine, threonine, methionine, and leucine), 50% less 3-hydroxyglutarate excretion, and a 3-fold lower hospitalization rate (0.8 versus 2.3 hospitalizations per patient per year). The relationship between arginine fortification and plasma lysine indicates that transport competition exists at both cerebrovascular and gastrointestinal barriers, suggesting their co-administration is key to efficacy. Monitoring the ratio between lysine and arginine in diet and plasma may prove a useful strategy for treating children with GA1.

Role of carnitine in disease

Carnitine is a conditionally essential nutrient that plays a vital role in energy production and fatty acid metabolism. Vegetarians possess a greater bioavailability than meat eaters. Distinct deficiencies arise either from genetic mutation of carnitine transporters or in association with other disorders such as liver or kidney disease. Carnitine deficiency occurs in aberrations of carnitine regulation in disorders such as diabetes, sepsis, cardiomyopathy, malnutrition, cirrhosis, endocrine disorders and with aging. Nutritional supplementation of L-carnitine, the biologically active form of carnitine, is ameliorative for uremic patients, and can improve nerve conduction, neuropathic pain and immune function in diabetes patients while it is life-saving for patients suffering primary carnitine deficiency. Clinical application of carnitine holds much promise in a range of neural disorders such as Alzheimer's disease, hepatic encephalopathy and other painful neuropathies. Topical application in dry eye offers osmoprotection and modulates immune and inflammatory responses. Carnitine has been recognized as a nutritional supplement in cardiovascular disease and there is increasing evidence that carnitine supplementation may be beneficial in treating obesity, improving glucose intolerance and total energy expenditure.

Mouse model of encephalopathy and novel treatment strategies with substrate competition in glutaric aciduria type I

Glutaric aciduria type I (GA-1) results from an inherited defect in a common step of lysine, hydroxylysine and tryptophan metabolism. This defect is associated with an age-dependent susceptibility to encephalopathy commonly preceded by non-specific childhood illnesses or fasting. The brain injury that develops with encephalopathic crisis in GA-1 is anatomically and symptomatically similar to Huntington's disease, affecting the striatum. The mechanism of injury remains poorly understood. Recently, an animal model of GA-1 encephalopathy was developed by providing GA-1 mice with added dietary lysine. This model shows age-dependent susceptibility similar to the human disease. Enhanced lysine accumulation and utilization in the immature brain correlates with increased glutaric acid levels and age-dependent susceptibility. Neurotransmitter and Krebs cycle intermediate depletion in this model represent novel findings toward uncovering the mechanism of neuronal injury. Additionally this mouse model is responsive to glucose analogous to human GA-1 and provides insight toward the mechanism of this effect. Together these findings led to a new treatment strategy of competing with brain lysine uptake that shows promising results. This research serves as a model for understanding blood brain barrier amino acid transport at critical stages of development and may help advance understanding of brain injury and development of treatments in other IEMs including urea cycle disorders.

Primary disorders of metabolism and disturbed fetal brain development

There exists a link between the in utero metabolic environment and the development of the fetal nervous system. Prenatal neurosonography offers a unique, noninvasive tool in the detection of developmental brain malformations and the ability to monitor changes over time. This article explores the association of malformations of cerebral development reported in association with inborn errors of metabolism, and speculates on potential mechanisms by which such malformations arise. The detection of cerebral malformations prenatally should lead to a search for both genetic etiologies and inborn errors of metabolism in the fetus. Improving the changes of an early diagnosis provides for timely therapeutic interventions and it is hoped a brighter future for affected children and their families.

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.

Glutaric aciduria type 1 presenting with epilepsy

Glutaric aciduria type 1 (GA-1, OMIM 608801) is an autosomal-recessive disorder resulting from a deficiency of glutaryl-CoA dehydrogenase (GCDH). Clinical expression usually involves an acute encephalopathic episode in infancy, followed by the development of severe dystonia-dyskinesia. Other presentations include mild developmental delay, macrocephaly, and subdural haematoma. Seizures may occur with the acute encephalopathy but are unusual in the long term, unless motor or cognitive difficulties are severe. We report a 6-year-old female who was referred with recurrent epileptic seizures that proved difficult to control with first-line anticonvulsants. There was no history of encephalopathy. She had no neurological or developmental abnormalities. The electroencephalogram was profoundly abnormal with slow background and mixed multifocal and generalized spike-and-wave discharges. Seizures deteriorated on valproic acid. Cranial magnetic resonance imaging showed widened Sylvian fissures. Metabolic investigations revealed GA-1. She has improved on a low-protein diet, carnitine, levetiracetam, and lamotrigine. This is the first report of epileptic seizures as the sole presenting feature of GA-1 and it potentially adds to the clinical spectrum of this disorder. Furthermore, the case emphasizes the role of metabolic investigation when first- or second-line treatment of epilepsy is unsuccessful.

Glutaric acidemia type I: a neurosurgical perspective. Report of two cases

Glutaric acidemia type I (GA-I) is a rare, autosomal recessive metabolic disorder that leads to severe dystonia, basal ganglia degeneration, and bilaterally enlarged anterior middle cranial fossae. The current management of this disease includes early diagnosis with newborn screening, prevention of catabolism, carnitine supplementation, and a strict dietary protein restriction. Neurosurgical evaluation and intervention may be necessary in patients with structural lesions associated with this disease. In this report, the authors present two pediatric patients with GA-I and discuss the neurosurgical aspects of this rare medical disorder.

Early detection of glutaric aciduria type I by newborn screening in Taiwan

BACKGROUND/PURPOSE

Glutaric aciduria type 1 (GA1) is an inborn error of lysine and tryptophan metabolism. There is a lack of initial diagnostic signs of the disease, but late treatment often results in severe neurologic impairment. In this study, we analyzed the results of screening for GA1 in a Chinese population.

METHODS

Dry blood spots were obtained at about 3 days of age from 357,307 newborns and tested for elevation of glutaryl (C5DC)-carnitine by tandem mass spectroscopy. A second sample of blood spots was required from those cases with abnormal elevation of C5DC-carnitine (higher than the cut-off value) (recall). If the results remained abnormal, those cases were referred for confirmation of the diagnosis and treatment.

RESULTS

Between August 2001 and February 2005, there were 40 cases with C5DC-carnitine more than 0.13 microM (the cut-off value), from whom a second sample of blood spots was obtained (recall rate, 0.02%); two cases were confirmed to be affected by GA1. Because of the low positive prediction rate using this cut-off value, we elevated the cut-off value slightly. Between February 2005 and August 2006, there were eight cases with C5DC-carnitine more than 0.22 microM from whom a second sample of blood spots was obtained (recall rate, 0.01%); three cases were confirmed to be affected by GA1. All five cases with persistent elevation of C5DC-carnitine were referred and diagnosis was confirmed in each, giving an incidence of 1 in 71,461 newborns. There were no false negatives. Magnetic resonance imaging studies obtained from four cases showed frontotemporal atrophy at the time of diagnosis. Two cases were followed for over 1 year, and under treatment with dietary control and carnitine supplementation, both had normal development and neither exhibited a frank episode of encephalopathic crisis.

CONCLUSION

With properly established cut-offs, GA1 can be successfully screened for in populations with a low incidence of the disease. Early treatment is likely to improve the outcome of cases discovered by screening.

Mechanism of age-dependent susceptibility and novel treatment strategy in glutaric acidemia type I

Glutaric acidemia type I (GA-I) is an inherited disorder of lysine and tryptophan metabolism presenting with striatal lesions anatomically and symptomatically similar to Huntington disease. Affected children commonly suffer acute brain injury in the context of a catabolic state associated with nonspecific illness. The mechanisms underlying injury and age-dependent susceptibility have been unknown, and lack of a diagnostic marker heralding brain injury has impeded intervention efforts. Using a mouse model of GA-I, we show that pathologic events began in the neuronal compartment while enhanced lysine accumulation in the immature brain allowed increased glutaric acid production resulting in age-dependent injury. Glutamate and GABA depletion correlated with brain glutaric acid accumulation and could be monitored in vivo by proton nuclear magnetic resonance (1H NMR) spectroscopy as a diagnostic marker. Blocking brain lysine uptake reduced glutaric acid levels and brain injury. These findings provide what we believe are new monitoring and treatment strategies that may translate for use in human GA-I.

Creatine decreases convulsions and neurochemical alterations induced by glutaric acid in rats

Glutaric acidemia type I (GA-I) is an inherited metabolic disease characterized by striatal degeneration, seizures, and accumulation of glutaric acid (GA). Considering that GA impairs energy metabolism and induces reactive species generation, we investigated whether the acute administration of creatine, an amino acid with antioxidant and ergogenic properties, protects against the seizures and neurochemical alterations (inhibition of Na(+),K(+)-ATPase and increased protein carbonylation) induced by the intrastriatal injection of GA (4 micromol/striatum). We also investigated whether creatine protected against the GA-induced inhibition of glutamate uptake in vitro. Creatine administration (300 mg/kg, p.o.) decreased seizures (evidenced by electrographic changes), protein carbonylation and Na(+),K(+)-ATPase inhibition induced by GA. However, creatine, at a dose capable of fully preventing GA-induced protein carbonylation (50 and 150 mg/kg, p.o.), did not prevent convulsions and Na(+),K(+)-ATPase inhibition, suggesting that the anticonvulsant activity of creatine in this experimental model is not related to its antioxidant action. Creatine also protected against the GA-induced inhibition of l-[(3)H]glutamate uptake in synaptosomes, suggesting that creatine may reduce the deleterious effects of GA by maintaining glutamate uptake in the synaptic cleft. Therefore, considering that creatine significantly attenuates the deleterious effects of GA assessed by behavioral and neurochemical measures, it is plausible to propose the use of this amino acid as an adjuvant therapy in the management of glutaric acidemia.

Heparan sulfate mediates neuroprotection from degeneration in experimental glutaric aciduria

Glutaric aciduria type 1 (GA1) is a childhood metabolic disorder associated with crises that lead to striatal necrosis. Although the disorder can be controlled with diet, there is no current treatment to ameliorate the neurodegeneration following a metabolic crisis. We hypothesized that heparan sulfate (HS) administration would stimulate neural stem cell proliferation by dimerizing with FGF-2 and binding to the FGF-2 receptor on neural stem cells, thus enhancing the number of newly generated neurons to repair damage following a metabolic crisis. In addition, FGF-2 is known to exert neuroprotective effects independent of neurogenesis, so HS may also have neuroprotective activities. To test these hypotheses, ibotenic acid was injected into the striatum of adult mice, mimicking the metabolic crisis and damage caused by glutaric aciduria. Daily doses of HS and bromodeoxyuridine (BrdU) or BrdU alone were administered starting 1 day after the ibotenic acid lesion. BrdU was used to label dividing cells. Fluorescent immunohistochemistry was used to quantify the lesion size and evaluate the phenotype of BrdU-positive cells. Intrastriatal administration of ibotenic acid resulted in a substantial striatal lesion that occupied 18.5% of the ipsilateral brain hemisphere. In contrast, animals treated with HS exhibited a lesion volume representing <1% of the ipsilateral brain hemisphere (ANOVA; p < 0.0001). Increased neurogenesis, however, was not observed in this group. These results suggest that HS administration 2 days after a "metabolic crisis" can ameliorate brain injury in an animal model of GA1. The neuroprotective mechanisms of HS, however, remain to be elucidated but may exert their actions indirectly through binding with FGF-2.

Analysis of organic acid markers relevant to inherited metabolic diseases by ultra-performance liquid chromatography/tandem mass spectrometry as benzofurazan derivatives

We describe a new approach applicable to the determination of organic acids that serve as diagnostic markers for several inherited metabolic disorders. We utilized liquid chromatography/tandem mass spectrometry for analysis of organic acid derivatives of a recently described benzofurazan reagent. The derivatization step was necessary to obtain organic acid derivatives suitable for analysis by reversed-phase liquid chromatography with high ionization efficiency for mass spectrometry in the positive-ion mode. In this work, a group of related dicarboxylic acid markers containing five or six carbon atoms were analyzed and validation was performed for glutaric and 3-hydroxyglutaric acids, the specific markers for glutaric acidemia type 1. Derivatization was achieved by reacting untreated urine with the derivatization reagent under mild conditions. The reaction mixture was analyzed on a C18 ultra-performance liquid chromatography (UPLC) column (50x2.1 mm, 1.7 microm) and detected in the multiple reaction monitoring mode in 5 min. Calibration curves were linear up to at least 1000 microM with detection limits for glutaric and 3-hydroxyglutaric acids of 0.025 and 0.02 microM, respectively (signal-to-noise ratio of 3). Intra-day (n=11) and inter-day (n=6) coefficients of variation were better than 11.2%. The assay was successfully applied to control (n=134) and glutaric acidemia type 1 (n=55) urine samples.

The potential of stem cell therapies for neurological diseases

As a novel neurotherapeutic strategy, stem cell transplantation has received considerable attention, yet little of this attention has been devoted to the probabilities of success of stem cell therapies for specific neurological disorders. Given the complexities of the cellular organization of the nervous system and the manner in which it is assembled during development, it is unlikely that a cellular replacement strategy will succeed for any but the simplest of neurological disorders in the near future. A general strategy for stem cell transplantation to prevent or minimize neurological disorders is much more likely to succeed. Two broad categories of neurological disease, inherited metabolic disorders and invasive brain tumors, are among the most likely candidates.

A diet-induced mouse model for glutaric aciduria type I

In the autosomal recessive human disease, glutaric aciduria type I (GA-1), glutaryl-CoA dehydrogenase (GCDH) deficiency disrupts the mitochondrial catabolism of lysine and tryptophan. Affected individuals accumulate glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in the serum and often suffer acute striatal injury in childhood. Prior attempts to produce selective striatal vulnerability in an animal model have been unsuccessful. We hypothesized that acute striatal injury may be induced in GCDH-deficient (Gcdh-/-) mice by elevated dietary protein and lysine. Here, we show that high protein diets are lethal to 4-week-old and 8-week-old Gcdh-/- mice within 2-3 days and 7-8 days, respectively. High lysine alone resulted in vasogenic oedema and blood-brain barrier breakdown within the striatum, associated with serum and tissue GA accumulation, neuronal loss, haemorrhage, paralysis, seizures and death in 75% of 4-week-old Gcdh-/- mice after 3-12 days. In contrast, most 8-week-old Gcdh-/- mice survived on high lysine, but developed white matter lesions, reactive astrocytes and neuronal loss after 6 weeks. Thus, the Gcdh-/- mouse exposed to high protein or lysine may be a useful model of human GA-1 including developmentally dependent striatal vulnerability.

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.

Glutaryl-CoA dehydrogenase deficiency and newborn screening: retrospective analysis of a low excretor provides further evidence that some cases may be missed

Glutaryl-CoA dehydrogenase deficiency (GA-I) is associated with the onset of irreversible, disabling dystonia between 3 and 18 months of age. Presymptomatic identification and treatment can prevent the devastating disability associated with this disorder. We report the retrospective analysis of the newborn blood spot of an affected child with a low excretor phenotype. The level of glutarylcarnitine was below the newborn screening program cut-off. This suggests that some cases of GA-I may be missed by newborn screening by tandem mass spectrometry.

The urinary excretion of glutarylcarnitine is an informative tool in the biochemical diagnosis of glutaric acidemia type I

Glutaric acidemia type I (GA-1) is a progressive neurodegenerative inborn error of metabolism that typically manifests acutely in infants during an intercurrent illness. The diagnosis is established biochemically by the detection of glutaric acid and 3-hydroxy glutaric acid in urine and glutarylcarnitine in plasma. However, some patients excrete only small amounts of glutaric acid and may be overlooked, especially if the plasma concentration of glutarylcarnitine is not elevated. To test the hypothesis that measuring the excretion of glutarylcarnitine may improve the recognition of GA-1 patients without significant glutaric aciduria, urine glutarylcarnitine was analyzed in 14 cases. Five of them lacked significant glutaric aciduria, 9 (of 10 available) had a normal plasma glutarylcarnitine concentration. As controls, we also evaluated 54 subjects with glutaric aciduria secondary to other causes (16-7509 mmol/mol creatinine; reference range: <15; no significant amounts of 3-hydroxy glutaric acid detectable). The excretion of glutarylcarnitine was significantly elevated in all GA-1 patients (14-522 mmol/mol creatinine; reference range: <5.2) and in none of the controls with glutaric aciduria. These findings suggest that the urinary excretion of glutarylcarnitine is a specific biochemical marker of GA-1 which could be particularly useful in the work up of patients with suggestive clinical manifestations but without glutaric aciduria and with normal plasma acylcarnitine profiles.

Synthesis of dicarboxylic acylcarnitines

Syntheses of malonyl, methylmalonyl, succinyl, glutaryl, methylglutaryl, dodecanedioyl and hexadecanedioyl carnitines are described. The dicarboxylic acylcarnitines were prepared from eight equivalents of cyclic anhydride or isopropylidene ester of the dicarboxylic acid and carnitine chloride in trifluoroacetic acid solution. Long chain dicarboxylic acylcarnitines were additionally purified by partitioning between water and n-butanol. Stable isotope labeled analogs, containing 3, 6 or 9 deuterium atoms, were also prepared. They are for use as standards in the electrospray ionization tandem mass spectrometric analysis of dicarboxylic acylcarnitines in samples from patients with inherited disorders of fatty acid oxidation.

Glutaric aciduria type 1: proton magnetic resonance spectroscopy findings

Glutaric aciduria type 1 is an inborn error of lysine, hydroxylysine, and tryptophan metabolism caused by deficiency of glutaryl-coenzyme A dehydrogenase. The disease often appears in infancy with an encephalopathic episode that results in acute basal ganglia and white matter degeneration. The neuroimaging findings in glutaric aciduria type 1 have been well defined. However, the changes in magnetic resonance spectroscopy, a noninvasive tool for identifying the biochemical state of the brain, are scarce in glutaric aciduria type 1. This report presents the magnetic resonance spectroscopy findings in a 19-month-old male with glutaric aciduria type 1. Magnetic resonance spectroscopy of right frontal white matter and right lentiform nuclei revealed decreased N-acetylaspartate/creatine ratio, slightly increased choline/creatine ratio, and increased myoinositol/creatine ratio, compared with the age-matched control patients. We thought that these changes were in accordance with neuroaxonal damage, demyelination, and astrocytosis in these areas. In conclusion, proton magnetic resonance spectroscopy provides a tool for assessing metabolic disturbances and the extent of brain damage noninvasively in glutaric aciduria type 1.

Bilateral pallidotomy for severe dystonia in an 18-month-old child with glutaric aciduria

Glutaric aciduria type 1 is an inborn error of metabolism due to deficiency of glutaryl-CoA dehydrogenase. This disorder mainly affects children. The majority of patients develop a dystonic-dyskinetic syndrome. The dystonia is painful and can cause significant disability. This report documents an 18-month-old child, the youngest reported, who underwent pallidotomy for disabling dystonia. The surgery improved dystonic symptoms, especially pain in this child with minor complications related to the procedure. Pallidotomy is a reasonable option for children with dystonic symptoms secondary to glutaric aciduria.

Hyperornithinemia, hyperammonemia, and homocitrullinuria syndrome with evidence of mitochondrial dysfunction due to a novel SLC25A15 (ORNT1) gene mutation in a Palestinian family

Hyperornithinemia, hyperammonemia, and homocitrullinuria (HHH) syndrome is caused by mutations in the SLC25A15 (ORNT1) gene encoding the mitochondrial ornithine transporter, but the mechanism of pathogenesis of the encephalopathy, spastic paraparesis and hepatopathy remains undetermined. HHH syndrome was diagnosed in a 2-year-old Palestinian boy with developmental delay and seizures, and subsequently in his 13-year-old brother with developmental delay. Direct sequencing of the PCR products of SLC25A15 exon amplifications revealed that both brothers were homozygous for a novel 446G deletion in exon 3 as well as for a 760A>T (I254L) polymorphism in exon 5, which is downstream of a premature termination codon produced by the frameshift resulting from the 446G deletion. The index patient had elevated liver enzymes as well as hyperalaninemia, lactic acidemia with an elevated lactate to pyruvate ratio, and increased urinary excretion of lactate, glutarate and Krebs cycle intermediates. These findings are indicative of mitochondrial dysfunction and are in accordance with ultrastructural studies showing increased numbers of large and bizarre mitochondria in liver, muscle, leukocytes and fibroblasts of some HHH patients. Neurologic and hepatic manifestations are characteristic of some primary mitochondrial disorders. Secondary mitochondrial dysfunction may contribute to the pathogenesis of these same features in HHH syndrome.

Evaluation of the child with cerebral palsy

Cerebral palsy (CP) is a common problem, occurring in about 2 to 2.5 per 1000 live births. The diagnosis of CP is based upon a history of abnormal motor development that is not progressive coupled with an examination (e.g. hypertonicity, increased reflexes, clonus) "placing" the lesion in the brain. In order to establish that a brain abnormality exists in children with CP that may, in turn, suggest an etiology and prognosis, neuroimaging is recommended with magnetic resonance imaging preferred to computed tomography. Metabolic and genetic studies should be obtained if there are atypical features in the history or on the examination. Detection of a brain malformation in a child with CP might suggest an underlying genetic or metabolic etiology. As cerebral infarction is high in children with hemiplegic CP, diagnostic testing for coagulation disorders should be considered. However, there is insufficient evidence at present to be precise as to what studies should be ordered. An electroencephalogram is not recommended unless there are features suggestive of epilepsy or a specific epileptic syndrome. As children with CP may have associated deficits of mental retardation, ophthalmologic and hearing impairments, speech and language disorders and oral-motor dysfunction, screening for these conditions should be part of the initial assessment.

Stability of malonylcarnitine and glutarylcarnitine in stored blood spots

Malonylcarnitine and glutarylcarnitine are important diagnostic metabolites in the screening of dried blood spots by tandem mass spectrometry. The stability of these compounds in spiked blood spots stored at room temperature was studied. Both showed biphasic curves. The malonylcarnitine concentration dropped to 61% in 38 days and averaged 51% +/- 5% for the next 81 days. Glutarylcarnitine dropped to 60% in 42 days and averaged 56% +/- 5% for the next 124 days.

Long-term follow-up, neurological outcome and survival rate in 28 Nordic patients with glutaric aciduria type 1

All 28 patients, 13 females and 15 males, with glutaric aciduria type 1 diagnosed between 1975 and 2001 in Denmark, Finland, Norway and Sweden were identified and studied retrospectively until 2001. Mass screening was not performed. Three were sibling cases. Prenatal enzymatic diagnosis performed in 11 pregnancies led to termination in one. The median follow-up time was 14 years. Six patients had died. At 10 years of age the cumulative survival rate was 89% and at 35 years 44%. The dominating neurological sign was dystonia in 20 and dyskinesia in 4. Three had only slight spastic signs and information was missing in one. The head circumference at birth was significantly larger than normal and increased significantly until 6 months of age. The onset was acute encephalopathic in 24 patients and insidious in 3. From the time of diagnosis, all patients but one were prescribed protein restriction and/or a diet low in lysine and tryptophan. Riboflavine and/or carnitine supplementation were given to 25. Neurological deficits did not improve on the offered treatment. Deterioration may have been averted by intense acute metabolic treatment in a few patients. Dystonia correlated significantly to absence of speech but not to cognitive function. Severe disability, including motor, cognitive and speech functions, correlated significantly with acute onset, dystonia and mortality, and weakly with a deteriorating course, but not with age at onset, diagnosis, or follow-up, nor to head size. Results from future population studies derived from mass screening will have to relate to clinical diagnostic series of the kind presented here.

Reduction of lysine intake while avoiding malnutrition--major goals and major problems in dietary treatment of glutaryl-CoA dehydrogenase deficiency

Treatment in glutaryl-CoA dehydrogenase deficiency, an inborn error of metabolism of lysine and tryptophan, is mainly based on restriction of lysine intake, supplementation of carnitine, and an intensification of therapy during intercurrent illnesses. The major principle of dietary treatment is to reduce the production of glutaric acid and 3-hydroxyglutaric acid by restriction of natural protein in general and of lysine in particular. In parallel to development, the growing child learns to utilize different protein sources, shifting the primarily milk-based diet to a mixed diet. The changes in nutritional demands and food composition during the first years of life greatly influence nutritional support for affected patients at different ages. This article highlights frequent pitfalls of dietary treatment for this disease and focuses on particular risks of malnutrition in terms of essential amino acids and micronutrients and/or excess intake of lysine between age 3 months and age 6 years. We conclude from the examples given that restriction of natural protein intake plus application of lysine-free amino acid mixtures minimizes the risk of malnutrition and allows a reliable control of protein and lysine intake and, thus, seems particularly recommendable during the vulnerable period for acute encephalopathic crises. The efficacy of these theoretical and experience-based approaches to dietary treatment of glutaryl-CoA dehydrogenase deficiency should be investigated in detail in prospective clinical studies.

Megalencephalic leukoencephalopathy with subcortical cysts

Megalencephalic leukoencephalopathy with subcortical cysts is one of the newly described white-matter disorders for which recognition has been brought about by advances in imaging technology. The essential diagnostic features include megalencephaly noted in infancy, motor disability in the form of spasticity, ataxia, occasional seizures, mild cognitive decline, and slow progression. Magnetic resonance imaging (MRI) shows bilateral extensive white-matter changes with cysts in the temporal regions. Based on the clinical and MRI features, megalencephalic leukoencephalopathy with subcortical cysts can be distinguished from other conditions (ie, Alexander's disease, Canavan's disease, glutaricaciduria type I) that present in infancy with megalencephaly. Megalencephalic leukoencephalopathy with subcortical cysts is an autosomal recessive disorder, and mutations in the MLC1 gene have now been shown to cause this condition. Several genotypic and phenotypic variations have been described. In India, megalencephalic leukoencephalopathy with subcortical cysts occurs predominantly in the Agarwal community. A common mutation in the MLC1 gene has been seen in 31 Agarwal patients, which suggests a founder effect.

Type I glutaric aciduria, part 1: natural history of 77 patients

Type I glutaric aciduria (GA1) results from mitochondrial matrix flavoprotein glutaryl-CoA dehydrogenase deficiency and is a cause of acute striatal necrosis in infancy. We present detailed clinical, neuroradiologic, molecular, biochemical, and functional data on 77 patients with GA1 representative of a 14-year clinical experience. Microencephalic macrocephaly at birth is the earliest sign of GA1 and is associated with stretched bridging veins that can be a cause of subdural hematoma and acute retinal hemorrhage. Acute striatal necrosis during infancy is the principal cause of morbidity and mortality and leads to chronic oromotor, gastroesophageal, skeletal, and respiratory complications of dystonia. Injury to the putamen is heralded by abrupt-onset behavioral arrest. Tissue degeneration is stroke-like in pace, radiologic appearance, and irreversibility. It is uniformly symmetric, regionally selective, confined to children under 18 months of age, and occurs almost always during an infectious illness. Our knowledge of disease mechanisms, though incomplete, is sufficient to allow a rational approach to management of encephalopathic crises. Screening of asymptomatic newborns with GA1 followed by thoughtful prospective care reduces the incidence of radiologically and clinically evident basal ganglia injury from approximately 90% to 35%. Uninjured children have good developmental outcomes and thrive within Amish and non-Amish communities.

Pediatric medicine and the genetic disorders of the Amish and Mennonite people of Pennsylvania

The Clinic for Special Children in Lancaster County, Pennsylvania, is a community-supported, nonprofit pediatric medical practice for Amish and Mennonite children who have genetic disorders. Over a 14-year period, 1988-2002, we have encountered 39 heritable disorders among the Amish and 23 among the Mennonites. We emphasize early recognition and long-term medical care of children with genetic conditions. In the clinic laboratory we perform amino acid analyses by high-performance liquid chromatography (HPLC), organic acid analyses by gas chromatography/mass spectrometry (GC/MS), and molecular diagnoses and carrier tests by polymerase chain reaction (PCR) amplification and sequencing or restriction digestion. Regional hospitals and midwives routinely send whole-blood filter paper neonatal screens for tandem mass spectrometry and other modern analytical methods to detect 14 of the metabolic disorders found in these populations as part of the NeoGen Inc. Supplemental Newborn Screening Program (Pittsburgh, PA). Medical care based on disease pathophysiology reduces morbidity, mortality, and costs for the majority of disorders. Among our patients who are homozygous for the same mutation, differences in disease severity are not unusual. Clinical problems typically arise from the interaction of the underlying genetic disorder with common infections, malnutrition, injuries, and immune dysfunction that act through classical pathophysiological disease mechanisms to influence the natural history of disease.