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In cultured fibroblasts of adrenoleukodystrophy (ALD) patients and most heterozygotes, concentrations of long-chain fatty acids (greater than C22) were significantly higher than in controls when cells were assayed 4-5 days after reaching confluence. Intermediate values were found in three independent cultures of a girl with manifest ALD, suggesting that a significant proportion of her fibroblasts does not express the defect. Though long-chain fatty acid concentrations in heterozygotes were somewhat higher than expected, suggesting a slight preponderance of defective cells, it may be too early to conclude that somatic selection is a consistent finding in cultured fibroblasts of ALD carriers.

We report on an 18-year-old Lithuanian girl with hepatosplenomegaly noticed at birth, which progressed thereafter. The patient had to wait about 17 years for an accurate diagnosis and appropriate therapy. Lactase deficiency, congenital cataract of the right eye, and osteoporosis were observed. Episodes of drowsiness were caused by intake of high-protein food. Laboratory findings included slight hyperammonaemia, high plasma Citr, Ala, Gly, Glu, Ser levels, as well as citrullinuria, lysinuria, glutaminuria, alaninuria, argininuria, prolinuria, hydroxyprolinuria, ornithinuria, and orotic aciduria. Aversion to high-protein diet strongly suggested a disorder resulting in hyperammonaemia. Citrullinaemia was suspected. Subsequently the diagnosis of LPI was made on the basis of biochemical and clinical features. Molecular genetic testing revealed a mutation in the SLC7A7 gene, confirming the diagnosis.

Despite early diagnosis and treatment, 35% of the patients with glutaric aciduria type I (GA I) develop severe neurologic damage. Glutaric acid and 3-hydroxyglutaric acid have been suspected to cause neurodegeneration. Lately, this has been questioned, however. We postulate that glutaconyl Coenzyme A (glutaconyl-CoA) is responsible for brain damage. Chemically, glutaconyl-CoA is an analogue of acrylyl-CoA, the parent substance of the extremely reactive class of acrylates. It is expected to react spontaneously with sulfhydryl groups, thus modifying membranes, disturbing enzyme functions and trapping glutathione. Enhanced production of glutaconyl-CoA together with lack of glutathione precipitates brain damage. Such a mechanism is supported by three findings. (1) The addition product of glutaconyl-CoA to cysteine is present in small amounts in normal human urine. (2) Reaction of methacrylyl-CoA with free sulfhydryl groups has been reported previously in a patient with 3-hydroxyisobutyryl CoA deacylase deficiency. (3) Glutathione has been found to be decreased in homozygous glutaryl-CoA dehydrogenase-deficient knock-out mice.

The mitochondrial trifunctional protein (MTP) is a multienzyme complex which catalyses three of the four chain-shortening reactions in the beta-oxidation of long-chain fatty acids. Clinically, failure of long-chain fatty acid beta-oxidation leads to hypoketotic hypoglycaemia associated with coma, hepatopathy, skeletal myopathy and cardiomyopathy. We report on consanguineous parents with six children, four of whom had unexpectedly died in Egypt during the neonatal period due to cardiomyopathy of unknown aetiology and respiratory failure. After moving to Germany, two further children died at the age of 4 months and 12 h, respectively, with signs of respiratory and cardiac failure, hydrops fetalis and acidosis. Analysis of acylcarnitine profiles in dried blood spots of the last two children by electrospray tandem mass spectrometry was indicative of a long-chain fatty acid beta-oxidation disorder. Both infants were homozygous for a novel missense mutation (976G-->C) within a highly conserved region of the MTP beta-subunit gene. Immunoblot analysis in chorionic villi obtained during the subsequent pregnancy demonstrated absence of MTP. In fibroblasts and liver, activities of all three catalytic units of MTP were markedly decreased, further confirming the diagnosis of MTP deficiency. CONCLUSION: the detected mutation (976G-->C) within the beta-subunit of the mitochondrial trifunctional protein gene destabilises the protein, leading to complete deficiency and a poor prognosis. Immunoblot analysis of mitochondrial trifunctional protein in chorionic villi may be a valuable tool for the prenatal diagnosis of the disorder when the molecular genetic defect is unknown

3-Methylglutaconic aciduria type I is an autosomal recessive disorder clinically characterized by various symptoms ranging from delayed speech development to severe neurological handicap. This disorder is caused by a deficiency of 3-methylglutaconyl-CoA hydratase, one of the key enzymes of leucine degradation. This results in elevated urinary levels of 3-methylglutaconic acid, 3-methylglutaric acid, and 3-hydroxyisovaleric acid. By heterologous expression in Escherichia coli, we show that 3-methylglutaconyl-CoA hydratase is encoded by the AUH gene, whose product had been reported elsewhere as an AU-specific RNA-binding protein. Mutation analysis of AUH in two patients revealed a nonsense mutation (R197X) and a splice-site mutation (IVS8-1G-->A), demonstrating that mutations in AUH cause 3-methylglutaconic aciduria type I

We report the identification of two new 7-year-old patients with 3-hydroxy-2-methylbutyryl-CoA dehydrogenase deficiency, a recently described inborn error of isoleucine metabolism. The defect is localized one step above 3-ketothiolase, resulting in a urinary metabolite pattern similar to that seen for deficiency of the latter. One patient has progressive neurodegenerative symptoms, whereas the clinical phenotype of the other patient is characterized by psychomotor retardation without loss of developmental milestones. A short-term biochemical response to an isoleucine-restricted diet was observed in both children.

We describe a 6-year-old girl admitted with acute muscular weakness and pain which made her unable to walk. Her parents reported a 4-year history of similar episodes which occurred once or twice a year and always resolved spontaneously. Laboratory investigations showed elevated serum creatine kinase which peaked at day 2 of the attack with 18,600 U/l. Carnitine palmitoyltransferase-II deficiency was suspected based on the determination of serum acylcarnitines by tandem mass spectrometry which showed a characteristic elevation of long-chain C16 and C18:1 acylcarnitines. The diagnosis was confirmed by impaired in-vitro palmitate oxidation in blood and the detection of a homozygous substitution S113L in the carnitine palmitoyltransferase-II gene. Conclusion: Carnitine palmitoyltransferase-II deficiency should be included in the differential diagnosis of isolated muscular weakness even when manifesting in early childhood.

UNLABELLED: In a female newborn presenting with rapid metabolic deterioration (hypoketotic hypoglycaemia and acidosis) clinically accompanied by a "sweaty feet"-odour, the excretion pattern of organic acids in the urine suggested on the fourth day of live multiple acyl-CoA-dehydrogenase-deficiency, a potentially lethal autosomal-recessively inherited inborn error of fatty acid beta-oxidation and of the metabolism of certain amino acids. Diagnosis was confirmed by tandem-mass-spectrometry of acyl-carnitines in blood. Despite the poor prognosis of neonatal-onset multiple acyl-CoA-dehydrogenase-deficiency, treatment with carnitine, riboflavine, and a high-energy diet low in fat and high in carbonhydrates resulted in clinical stabilization. The infant survived various infection-associated decompensations and developed satisfyingly up to the age of 15 months, when another metabolic crisis resulted in multiorgan failure and death. DISCUSSION: Patients with neonatal-presenting multiple acyl-CoA-dehydrogenase-deficiency but without severe malformations may survive the first months of life. Tandem mass-spectrometry is a suitable tool to differentiate between multiple acyl-CoA-dehydrogenase-deficiency and other defects of fatty acid beta-oxidation.

A mildly retarded infant with failure to thrive developed hypoglycaemia, focal seizures, respiratory failure and hemiparesis during a febrile episode at the age of 16 months. A brain scan was initially normal and showed hemilateral focal edema and gliosis at later stages. 3-Methylcrotonyl-CoA carboxylase deficiency was suggested by elevated urinary excretion of 3-hydroxyisovaleric acid and 3-methylcrotonylglycine, and confirmed by enzyme assays. The patient was treated with protein restriction and carnitine and remained stable during the following 5 years. Hemiparesis and some developmental delay persisted. In acute focal brain disease, metabolic disorders must be considered. 3-Methylcrotonyl-CoA carboxylase deficiency adds to the list of possible causes of "metabolic stroke".

The clinical and biochemical findings in a family with late-onset holocarboxylase synthetase (HCS) deficiency are described. The index patient had two life-threatening episodes of metabolic decompensation at the age of 13 and 18 months with ketotic hypoglycaemia, vomiting and progressive loss of consciousness. The child recovered without biotin therapy. Organic aciduria characteristic of multiple carboxylase deficiency (MCD) was found, however, the key metabolites were only slightly elevated in some samples. Biotinidase deficiency was considered but excluded by the finding of normal plasma biotinidase activity. The correct diagnosis was made only at the age of 19 months when severe MCD was found in lymphocytes in the presence of normal plasma biotin concentration. HCS deficiency was confirmed by fibroblast studies. Biotin therapy (20 or 40 mg/day) prevented further episodes and normalized biochemical parameters with so far normal development. During two subsequent pregnancies, 10 mg biotin/day was administered to the mother from the 20th week of gestation. At delivery plasma biotin in cord blood samples was 3–4 times higher than in maternal plasma. The 2nd child was unaffected. In the 3rd pregnancy prenatal diagnosis was performed at 16 weeks of gestation. The concentration of methylcitrate in amniotic fluid was within the normal range and that of 3-hydroxyisovalerate only slightly elevated. However, enzyme assays in cultured amniotic fluid cells were consistent with an affected fetus. At birth, carboxylase activities in lymphocytes of this newborn were only moderately decreased to 37% of mean normal. HCS deficiency was confirmed postnatally in fibroblasts. Development remains normal on biotin therapy (20 mg/day). Conclusion Prenatal diagnosis in families with milder forms of HCS deficiency has to be performed by enzyme assays in cultured amniotic cells since organic acid analysis of amniotic fluid may be inconclusive in affected fetuses. Biotin administered prenatally is effectively taken up by the fetus and prevents functional deficiency of the carboxylases in an affected newborn.

Ornithine transcarbamylase (OTC) deficiency is the most common urea cycle defect. The clinical presentation in female manifesting carriers varies both in onset and severity. We report on a female with insulin dependent diabetes mellitus and recurrent episodes of hyperammonemia. Since OTC activity measured in a liver biopsy sample was within normal limits, OTC deficiency was initially excluded from the differential diagnoses of hyperammonemia. Due to moderately elevated homocitrulline excretion, hyperornithinemia-hyperammonemia-homocitrullinuria-syndrome was suggested, but further assays in fibroblasts showed normal ornithine utilization. Later, when mutation analysis of the OTC gene became available, a known pathogenic missense mutation (c.533C>T) in exon 5 leading to an exchange of threonine-178 by methionine (p.Thr178Met) was detected. Skewed X-inactivation was demonstrated in leukocyte DNA. In the further clinical course the girl developed marked obesity. By initiating physical activities twice a week, therapeutic control of both diabetes and OTC deficiency improved, but obesity persisted. In conclusion, our case confirms that normal hepatic OTC enzyme activity measured in a single liver biopsy sample does not exclude a clinical relevant mosaic of OTC deficiency because of skewed X-inactivation. Mutation analysis of the OTC gene in whole blood may be a simple way to establish the diagnosis of OTC deficiency. The joint occurrence of OTC deficiency and diabetes in a patient has not been reported before.

Succinic semialdehyde dehydrogenase (SSADH) deficiency is an autosomal recessive disease involving the catabolism of the neurotransmitter gamma-aminobutyric acid (GABA). The main symptoms include retardation of psychomotor and language development, muscle hypotonia and non-progressive ataxia. Therapy consisting of approximately 75 mg/kg per day of vigabatrin, an irreversible inhibitor of GABA-transaminase, is reported to lead to some improvement of the clinical condition in affected patients. We report on a 12-year-old boy with SSADH deficiency who, when treated with 75 mg/kg per day of vigabatrin, showed marked amelioration of symptoms but also EEG changes and two generalized seizures. On discontinuing vigabatrin therapy, the seizures resolved and the EEG improved, but the patient's clinical condition deteriorated to its pre-treatment state. A stable EEG without the recurrence of seizures as well as renewed improvement of cognitive and behavioural functions was achieved with a reduced vigabatrin dose of 25 mg/kg per day. We conclude that vigabatrin in SSADH deficiency should be administered in a gradually increasing dosage combined with frequent evaluation of the clinical condition and the EEG.

Comprehensive data on 30 patients with propionic acidaemia, diagnosed by selective screening for inborn errors of metabolism, are presented. The most valuable diagnostic metabolites found were methylcitric-, 3-hydroxypropionic-, and 2-methyl-3-oxovaleric acids. Hyperlysinaemia and hyperlysinuria are also characteristic findings in this disease. The metabolic pattern found in propionic acidaemia is discussed extensively as are enzymatic findings. Residual activity of propionyl-CoA carboxylase is neither a predictive marker for severity nor for outcome of the disease. Propionate fixation assays were less reliable for confirmation of propionic acidaemia and of no prognostic value. Clinical presentation of the disease is discussed in detail. Besides the well-known unspecific findings (poor appetite, feeding difficulties, vomiting, dehydration, weight loss, muscular hypotonia, dyspnoea, somnolence, apathy, convulsion, coma, severe metabolic acidosis, hyperammonaemia) various skin abnormalities have been detected in about 50% of all patients. In 27% "dermatitis acidemica" was found.

Serial trans-fontanellar sonographic examination in a patient with glutaric aciduria type I (GA I) demonstrated that the typical frontotemporal cerebral atrophy developed postnatally within three months paralleling the onset of dystonic symptoms. Pathogenesis of the accompanying macrocephaly remains unclear and can form a diagnostic pitfall. Diet low in lysine and tryptophan led to a dramatic fall in urinary glutaric acid (GA) excretion but as in other patients with GA I did not substantially influence clinical symptoms and course. We determined unchanged levels of GA in plasma and cerebrospinal fluid resulting from variable renal tubular secretion and reabsorption of GA. Monitoring urinary excretion of GA appears inappropriate to control dietary treatment in GA I. Substitutive correction of secondary carnitine depletion seems to protect from deleterious metabolic crises. Treatment with valproic acid resulted in a rise of GABA-concentration in cerebrospinal fluid but did not ameliorate clinical symptoms. This finding is in contrast with the hypothesis that inhibition of cerebral GABA-synthesis by GA is responsible for the development of dystonia in GA 1. Although we observed impressing fluctuation of dystonic symptoms, levodopa did not show therapeutic effects. The extreme variability in the severity of neurologic disease in metabolically identical individuals leads to a "two-hit"-hypothesis.

Routine screening for organic acids revealed increased and isolated urinary excretion of L-2-hydroxyglutaric acid in 8 mentally retarded patients from five unrelated families, including three pairs of siblings. L-2-Hydroxyglutaric acid concentration was also found to be increased in the cerebrospinal fluid (CSF) and to a lesser extent in plasma. The only other biochemical abnormality was an increased concentration of lysine, both in plasma and in CSF. No organic acid abnormality was found on screening of asymptomatic family members. Patients were of either sex, and became symptomatic during childhood, with moderate to severe mental deficiency in all and definite cerebellar dysfunction in 7. Magnetic resonance imaging revealed an identical abnormal pattern with subcortical leukoencephalopathy, cerebellar atrophy, and signal changes in the putamina and dentate nuclei, in all patients. No specific biochemical function or catabolic pathway involving L-2-hydroxyglutaric acid is known in mammals, including humans. Preliminary loading and dietary studies failed to reveal the origin of the compound. The elevated CSF/plasma ratio suggests that it is in part generated within the central nervous system. This report describes a novel inherited neurometabolic disease, probably autosomal recessive, with distinct clinical, biochemical, and neuroimaging features.

Clinical course, diagnostic and therapeutic management, and neurodevelopmental outcome were evaluated in 11 patients with glutaryl-coenzyme A dehydrogenase deficiency. In 9 patients macrocephalus was present at or shortly after birth and preceded the neurological disease. In 7 children an acute illness resembling encephalitis appeared after a period of normal development; 2 had developmental delay and progressive "dystonic cerebral palsy." Later, all 9 displayed typical signs of a disorder of the basal ganglia. In 1 patient with macrocephalus the disorder was diagnosed before the onset of neurological disease; in another it was diagnosed prenatally. Computed tomography and magnetic resonance imaging scans revealed severe generalized cerebral atrophy, most striking in the frontal and temporal lobes in 10 patients. Further deterioration was halted after initiation of treatment consisting of low-protein diets, special formulas low in lysine and tryptophan, and supplements of riboflavin and L-carnitine. Only 1 patient showed a slight clinical improvement. Later, dietary therapy was discontinued in 2 older patients and relaxed in a third without observed adverse effects. Two patients in whom treatment could be initiated before the onset of neurological symptoms have developed normally. However, duration of follow-up (6 and 29 months) does not yet allow classification of glutaryl-coenzyme A dehydrogenase deficiency as a treatable disorder. Total body production of glutaric acid, reflected in the daily urinary output, was efficiently reduced by therapeutic measures. Levels of glutaric acid in plasma and cerebrospinal fluid remained unchanged, which may in part explain the overall unsatisfactory outcome. All patients presented with a severe secondary deficiency of carnitine. L-Carnitine appears to play an important pathobiochemical role in the pathogenesis of the disorder. It is concluded that glutaryl-coenzyme A dehydrogenase deficiency is an acute to subacute neuropathic disorder of infancy or early childhood. Later in the course of the disease further deterioration appears to subside. The lack of significant metabolic derangements may cause this disorder to remain frequently undiagnosed. Glutaryl-coenzyme A dehydrogenase deficiency should have high priority in the differential diagnosis of any child with acute profound dyskinesia, subacute motor delay accompanied by increasingly severe choreoathetosis, and dystonia. It should especially be considered when there is macrocephalus in an infant together with progressive atrophic changes on computed tomography or nuclear magnetic resonance imaging, as neurological handicap can potentially still be prevented.

In order to study the glycosidic conjugation of chenodeoxycholic, hyodeoxycholic, and ursodeoxycholic acids in patients with cholestasis after oral administration of pharmacological amounts of the respective bile acids avoiding the application of radioactive tracers we synthesized [24-13C]chenodeoxycholic, [24-13C]hyodeoxycholic, and [24-13C]ursodeoxycholic acids. The reaction intermediates of the bile acid syntheses were characterized by infrared spectroscopy. Purity was confirmed using thin-layer chromatography as well as gas chromatography-mass spectrometry. The 13C atom excess of approximately 90% of the synthesized bile acids was the same as the 13C atom excess of the sodium [13C]cyanide used for the labeling reaction confirming the successful synthesis. After oral administration of 0.5 g of [24-13C]ursodeoxycholic acid to a healthy volunteer, 13C label was detected in the nonamidated and glycine- or taurine conjugated glucosides and the N-acetylglucosaminide of ursodeoxycholic acid in urine. This establishes ursodeoxycholic acid as the first bile acid so far known to undergo both of the recently described glycosidic conjugation reactions in humans.

Udgivelsesdato: 2008-Aug Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is an inherited disorder of mitochondrial fatty acid oxidation associated with variations in the ACADS gene and variable clinical symptoms. In addition to rare ACADS inactivating variations, two common variations, c.511C > T (p.Arg171Trp) and c.625G > A (p.Gly209Ser), have been identified in patients, but these are also present in up to 14% of normal populations leading to questions of their clinical relevance. The common variant alleles encode proteins with nearly normal enzymatic activity at physiological conditions in vitro. SCAD enzyme function, however, is impaired at increased temperature and the tendency to misfold increases under conditions of cellular stress. The present study examines misfolding of variant SCAD proteins identified in patients with SCAD deficiency. Analysis of the ACADS gene in 114 patients revealed 29 variations, 26 missense, one start codon, and two stop codon variations. In vitro import studies of variant SCAD proteins in isolated mitochondria from SCAD deficient (SCAD-/-) mice demonstrated an increased tendency of the abnormal proteins to misfold and aggregate compared to the wild-type, a phenomenon that often leads to gain-of-function cellular phenotypes. However, no correlation was found between the clinical phenotype and the degree of SCAD dysfunction. We propose that SCAD deficiency should be considered as a disorder of protein folding that can lead to clinical disease in combination with other genetic and environmental factors.

Propionic acidemia is often manifested during the neonatal period with vomiting, failure to thrive, lethargy, and hyperammonemic coma when catabolism is prolonged. Mild lactic acidosis frequently accompanies metabolic decompensation. We present two patients with propionic acidemia whose initial manifestation was complicated by severe lactic acidosis caused by thiamine deficiency, which resulted from an inadequate supply of, and an increased need for, thiamine during metabolic stress. To prevent acute thiamine deficiency, we propose early vitamin supplementation during treatment of any severe metabolic decompensation accompanied by insufficient food intake.

Deficiency of guanidinoacetate methyltransferase (GAMT), the first described creatine biosynthesis defect, leads to depletion of creatine and phosphocreatine, and accumulation of guanidinoacetate in brain. This results in epilepsy, mental retardation, and extrapyramidal movement disorders. Investigation of skeletal muscle by proton and phosphorus magnetic resonance spectroscopy before therapy demonstrated the presence of considerable amounts of creatine and phosphocreatine, and accumulation of phosphorylated guanidinoacetate in a 7-year-old boy diagnosed with GAMT deficiency, suggesting separate mechanisms for creatine uptake and synthesis in brain and skeletal muscle. The combination of creatine supplementation and a guanidinoacetate-lowering therapeutic approach resulted in improvement of clinical symptoms and metabolite concentrations in brain, muscle, and body fluids.

Persistent excretion of elevated amounts of ethylmalonic acid (EMA) with or without concomitant acylglycinuria is a relatively frequent finding during selective screening for inborn errors of metabolism in our laboratory. One is struck by the number of cases within this group that show similar clinical features: muscular hypotonia, motor retardation, ataxia, spastic diplegia or tetraparesis develop gradually after febrile infections with vomiting and somnolence. In 3 out of 20 patients initially observed, in whom we have succeeded in obtaining the appropriate material, partial cytochrome c oxidase (COX) deficiency (McKusick 220110) was detected in muscle biopsies

3-Methylglutaconyl (3-MG)-CoA hydratase (EC 4.2.1.18) catalyses the fourth step in leucine catabolism by converting 3-MG-CoA into 3-hydroxy-3-methylglutaryl (3-HMG)-CoA. Deficiency of 3-MG-CoA hydratase has been defined as 3-methylglutaconic (3-MGC) aciduria type I (McKusick 250950) presenting with increased urinary excretion of 3-MGC, 3-methylglutaric (3-MGR) acid and 3-hydroxyisovaleric (3-HIV) acid and with normal amounts of 3-hydroxy-3-methylglutaric (3-HMG) acid. Additional types of 3-MGC aciduria with normal activities of 3-MG-CoA hydratase have been classified (Gibson et al 1993): type II seems to be of X-linked inheritance and is associated with cardiomyopathy, growth retardation and neutropenia (Kelley et al 1989). Type III has been described as the Costeff Iraqi-Jewish optic atrophy syndrome (Costeff et al 1989). Another type (type IV, unclassified) comprises a heterogeneous group of patients with progressive neurological symptoms. In contrast to 3-MGC aciduria type I, the origin of the specific organic aciduria in these entities is unknown. Since 3-HIV acid seems to be excreted only in patients with deficient 3-MG-CoA hydratase activity, it is an important parameter for differentiation between type I and the other types. Owing to the variability of the clinical picture of the nine patients with deficiency of 3-MG-CoA hydratase reported so far, a specific phenotype of 3-MGC aciduria type I has not yet been established. There seem to be a benign and a more severe form: in several patients the only symptoms were delayed speech development, mild psychomotor retardation and attention deficits (Duran et al 1982; Gibson et al 1992; Sewell et al 1999). Three of the reported patients, however, presented with severe neurological symptoms including spastic quadriplegia, dystonic movements, hypotonia and marked psychomotor retardation in two patients as well as coma and seizures during an episode of Reye syndrome in another patient with speech retardation (Gibson et al 1998; Hou and Wang 1995; Shoji et al 1999). We report on a new patient with a mild clinical presentation of 3-MGC aciduria type I.

Hawkinsinuria is a rarely diagnosed autosomal dominantly transmitted inborn error of tyrosine metabolism with impaired conversion of 4-hydroxyphenylpyruvate to homogentisate. As a consequence of the defective 4-hydroxyphenylpyruvate dioxigenase activity, large amounts of the unusual, ninhydrin-positive amino acid hawkinsin and later on in life 4-hydroxycyclohexylacetic acid are formed and excreted. Clinically the disease is characterised mainly by chronic metabolic acidosis and severe growth retardation as a result of protein overload. As the ability to form 4-hydroxycyclohexylacetic acid and thereby to cope with the still not very well defined reactive and toxic intermediates increases, clinical symptoms vanish. We report here a new patient with hawkinsinuria having experienced a series of admissions because of unclear hepatopathy, growth retardation, and renal tubular acidosis. Conclusion Prolonged tyrosyluria in the newborn and young baby should cause the clinical chemist not only to exclude tyrosinaemia, galactosaemia, and fructose intolerance but also to look carefully for hawkinsin in the aminoacid chromatogram.

Inspiratory stridor of unknown origin was the␣leading clinical symptom in an 11-month-old boy. The stridor increased over a period of 4 weeks, and assisted ventilation became necessary. Selective urinary screening by gas chromatography/mass spectrometry analysis revealed excretion of ethylmalonic and 3-OH-isovaleric acid and of n-isobutyryl-, n-2-methylbutyryl-, n-isovaleryl-, n-hexanoyl- and n-suberylglycine. Neither hypoglycaemia nor metabolic acidosis were noticed. Treatment with 200 mg of riboflavin per day led to a␣dramatic clinical improvement with restoration of normal respiration and an increase in muscular tone within 2 months. During this period, metabolite excretion in urine completely normalized. Riboflavin-sensitive multiple acyl-CoA dehydrogenation deficiency was confirmed in cultured fibroblasts. With riboflavin supplementation, the development of the child has been favourable, with normal school attendance now at an age of 9 years. Conclusion As respiratory symptoms might precede other symptoms in disorders of mitochondrial oxidation, we propose determination of urinary organic acids in all cases of unexplained laryngeal stridor.

Objectives. To further define the clinical spectrum of the disease for pediatric and metabolic specialists, and to suggest that the general pediatrician and pediatric neurologist consider succinic semialdehyde dehydrogenase (SSADH) deficiency in the differential diagnosis of patients with (idiopathic) mental retardation and emphasize the need for accurate, quantitative organic acid analysis in such patients. Patients. The clinical features of 23 patients (20 families) with SSADH deficiency (4-hydroxybutyric aciduria) are presented. The age at diagnosis ranged from 3 months to 25 years in the 11 male and 12 female patients; consanguinity was noted in 39% of families. Outcome Measurements. The following abnormalities were observed (frequency in 23 patients): motor delay, including fine-motor skills, 78%; language delay, 78%; hypotonia, 74%; mental delay, 74%; seizures, 48%; decreased or absent reflexes, 39%; ataxia, 30%; behavioral problems, 30%; hyperkinesis, 30%; neonatal problems, 26%; and electroencephalographic abnormalities, 26%. Associated findings included psychoses, cranial magnetic resonance or computed tomographic abnormalities, and ocular problems in 22% or less of patients. Therapy with vigabatrin proved beneficial to varying degrees in 35% of the patients. Normal early development was noted in 30% of patients. Conclusions. Our data imply that two groups of patients with SSADH deficiency exist, differentiated by the course of early development. Our recommendation would be that accurate, quantitative organic acid analysis in an appropriate specialist laboratory be requested for any patients presenting with two or more features of mental, motor, or language delay and hypotonia of unknown cause. Such analyses are the only definitive way to diagnose SSADH deficiency; the diagnosis can be confirmed by determination of enzyme activity in white cells from whole blood. We think that increased use of organic acid determination will lead to increased diagnosis of SSADH deficiency and a more accurate representation of disease frequency. As additional patients are identified, we should have a better understanding of both the metabolic and clinical profiles of SSADH deficiency.

A patient with early-onset 3-methylcrotonyl coenzyme A carboxylase (MCC) deficiency showing a severe clinical course is described. Abnormal eye and head movements suggestive of seizures were noticed soon after birth. Tonic convulsions at the age of 10 weeks led to admission. Urinary organic acid analysis using gas chromatography-mass spectrometry at 3 months of age revealed elevated concentrations of 3-hydroxyisovaleric acid (3HIVA) and 3-methylcrotonylglycine but normal levels of lactate, 3-hydroxypropionate and methylcitrate suggesting isolated MCC deficiency. This was confirmed by enzyme assays in lymphocytes and cultured skin fibroblasts: MCC activity was virtually undetectable whereas activities of propionyl-CoA and pyruvate carboxylases were within the normal range. A low protein (0.8-1.5 g/kg/day) diet supplemented with a leucine-free amino acid mixture resulted in a marked decrease of 3HIVA excretion. L-Carnitine and biotin administration had no effect on the clinical condition or metabolite excretion. Supplementation with glycine resulted in only a temporary fall of 3HIVA excretion and was therefore discontinued. L-Carnitine therapy was reintroduced later because of secondary carnitine deficiency. Compliance with treatment was poor until the age of 27 months resulting in a severe episode with seizures and coma. The general clinical condition of the patient was always good but his psychomotor development was delayed and seizures were not continuously under good control due to poor therapy compliance. The boy is now 10.5 years old and attending a school for children with learning handicaps.Isolated MCC deficiency of early-onset is a rare condition exhibiting a more severe clinical course than the later-onset form described in most other cases. The prognostic value of 3 HIVA measurements in CSF and serum should be evaluated in future cases.

BackgroundGlutaryl-CoA dehydrogenase deficiency (GDD) is. recessively inheritedneurometabolic disorder associated with encephalopathic crises andsevere extrapyramidal symptoms. Treatment regimens including glucoseand electrolyte infusions during acute illnesses, oral carnitinesupplementation and/or a low-protein or lysine-restricted diet havebeen recommended, but their efficacy has been documented only on ananecdotal basis.Subjects and methodsWe conducted a retrospective analysis of 57 patients with provenGDD-relating appearance and severity of neurological disease to age andclinical status at diagnosis, glutaric acid levels in body fluids, anddifferent treatment regimens.ResultsThirty-six patients were diagnosed after the onset of neurologicaldisease (symptomatic group), twenty-one before (presymptomatic group).Carnitine levels were found to be reduced in all patients at diagnosis.In the symptomatic group, macrocephaly had been present around birthand was followed by rapid postnatal head growth in 70 % of thechildren. The patients often showed symptoms such as hypotonia,irritability, and jitteriness followed by an acute encephalopathiccrisis occurring on average at 12 months of age. Common neuroimagingfindings included frontotemporal atrophy, subependymal pseudocysts,delayed myelination, basal ganglia atrophy, chronic subdural effusionsand hematomas. In four patients the latter two findings were initiallymisinterpreted as resulting from child abuse. Other importantmisdiagnoses in older siblings who were affected and went undiagnosedinclude postencephalitic cerebral palsy, dystonic cerebral palsy andsudden infant death syndrome. Metabolic treatment did not convincinglyimprove the neurological disease, although it may have preventedfurther deterioration. Symptomatic treatment with baclofen orbenzodiazepines was effective in reducing muscle spasms.Children in the presymptomatic group were diagnosed because offamiliarity for the disease (n = 13), macrocephaly and/or additionalminor neurological signs in infancy (n = 6), or acute encephalopathy,which was fully reversible after prompt treatment (n = 2). Afterdiagnosis, all children were treated with oral carnitine, fluidinfusion during intercurrent illnesses and, in addition, a diet wasstarted in 13 of the 21 children. All 21 children except one (bornprematurely at 31 weeks) have continued to develop normally up to now.Mean age at report is 6.3 years with a range from 6 months to 14.8years. In older patients, the neuroradiological changes, present ininfancy as in the symptomatic patients, became less prominent and inone girl disappeared.ConclusionsIn presymptomatic children with GDD, the onset of neurological diseasecan be prevented by vigorous treatment of catabolic crises duringillnesses together with carnitine supplementation. The importance ofdietary therapy remains unclear and needs further evaluation. Thepotential treatability of GDD calls for increased attention to earlypresenting signs in order to recognize the disorder and to initiatetreatment before the onset of irreversible neurological disease.

Since 1973 the University Children's Hospital of Freiburg has provided a service devoted to selective screening for inborn errors of metabolism with particular emphasis on organic acidurias. Patients to be investigated are preselected by local clinical paediatricians. Between 1973 and the end of 1990, 46,700 specimens from approximately 40,000 patients were screened by the methods listed in Table 1. A total of 464 cases were found consisting of 51 different diseases, 242 cases of 23 different organic acidurias and 222 cases of 28 other inborn errors of metabolism. The number of cases diagnosed parallels the number of patients investigated showing that there is still a real demand for metabolic screening. The number of children to be investigated is steadily increasing. Using the presented and already published data an appraisal of the overall incidence of all organic acidurias (1:6700) has been made as well as of the frequencies of the most common types of these disorders.

L-2-Hydroxyglutaric acidaemia represents a newly defined inborn error of metabolism, with increased levels of L-2-hydroxyglutaric acid in urine, plasma and cerebrospinal fluid. The concentration in cerebrospinal fluid is higher than in plasma. The other consistent biochemical finding is an increase of lysine in blood and cerebrospinal fluid, but lysine loading does not increase L-2-hydroxyglutaric acid concentration in plasma. This autosomal recessively inherited disease is expressed as progressive ataxia, mental deficiency with subcortical leukoencephalopathy and cerebellar atrophy on magnetic resonance imaging. Since these features were described in 8 patients by Barth and co-workers in 1992, 4 more patients with similar findings have been diagnosed and added to the present series. L-2-Hydroxyglutaric acid is found in only trace amounts on routine gas chromatographic screening in normal persons, and its origin, its fate and even its relevance to normal metabolism are unknown. Therefore its catabolism was studied in normal liver. Incubation of rat liver with L-2-hydroxyglutaric acid did not produce H2O2, which excluded (peroxisomal) L-2-hydroxyacid oxidase as the main route of catabolism. However, L-2-hydroxyglutaric acid is rapidly dehydrogenated if NAD+ is added as a co-factor to the standard reaction medium. This could also be demonstrated in human liver. The preliminary evidence for this enzyme activity in rats and humans, L-2-hydroxyglutaric acid dehydrogenase, is given. Further investigations are required to clarify the possible relevance to the metabolic defect in L-2-hydroxyglutaric acidaemia.

G. F. HOFFMANN 1, F. K. T~:Evz 1, P. G. BARTH 2, H.-J. BOHLES 3, W. LEHNERT 4, E. CHRISTENSEN 5, J. VALK 6, D. RATING 1 and H. J. BREM~rt 1 Departments of Paediatrics, 1 University of Heidelberg, Im Neuenheimer Feld 150, D-6900 Heidelberg, Federal Republic of Germany; 2University of Amsterdam, The Netherlands; 3 University of Frankfurt, FRG; 4University of Freiburg, FRG; SDepartment of Clinical Genetics, University of Copenhagen, Denmark; 6Department of Radiology, Free University of Amsterdam, The Netherlands

Sir—We support the statement by David A Grimes and Kenneth F Schulz (March 9, p 881) that certain features of screening tests are frequently overlooked. However, we disagree with their definition of screening as being tests done among apparently well people to identify those at an increased risk of a disease or disorder. They distinguish between screening and case finding by classifying the latter as looking for additional illnesses in patients with existing medical disorders. These definitions do not match the screening situation in identifying the diagnosis of inborn errors of metabolism, a specialty that is primarily associated with paediatrics, but also important for other areas. Limited numbers of such inherited diseases (including phenylketonuria, which Grimes and Schulz mention as an example) are detected in the neonatal screening programmes now offered in most industrialised countries. These programmes are compatible with the definition of screening they provide. However, metabolic screening includes not only general neonatal screening, but also selective screening done because of clinical indications in symptomatic individuals. Selective screening is not looking for additional illnesses, but rather aiming to identify the primary diagnosis and trying to reveal the underlying cause of clinical symptoms. This is done by analyses of several groups of metabolites. Selective screening for genetic metabolic disorders is offered by an increasing number of laboratories throughout the world. The proportion of diagnoses identified by selective screening is generally not higher than a few percent of the patients studied. This rate, however, depends very much on the expertise of the clinicians selecting the patients to be screened. A case-finding approach rather than selective screening may be appropriate only if the clinical suspicion is strong for a certain inborn error of metabolism.

A variant form of maple syrup urine disease (grade II) in a twelve year old boy is reported. The clinical picture was characterized by seizure-like episodes of confusion and intermittent ataxia. The diagnosis was made by showing an increased excretion of branched-chain alpha-hydroxy acids as well as evaluated plasma concentrations of the branched-chain aminoacids and alpha-ketoacids. There was a decrease of leucine degradation in cultured fibroblasts to 5 to 6% of normal. The treatment with thiamine-hydrochlorid remained without any clinical or biochemical effect in our patient. Further neurologic symptoms during acute episodes of vomiting could be avoided by dietary protein restriction and early parenteral glucose supplementation.

Clinical course and special diagnostic procedures in a 7 1/2 weeks old dystrophic infant with propionic acidemia are described. The disorder manifested with vomiting and diarrhea within the first week of life when the child was on a cow milk formula. Parenteral nutrition with glucose and electrolytes led to improvement. When oral nutrition with a cow milk formula was implemented again, an acute deterioration with diarrhoea and vomiting occurred. Thus, a diagnosis of cow milk allergy was suggested. There was also a severe muscular hypotony. Oral nutrition with a soybean formula did not prevent further clinical deterioration. At 7 1/2 weeks of age the patient died with symptoms of cardiogenic shock. The correct diagnosis was considered too late and confirmed post mortem. Clinical symptoms in the neonatal period like vomiting, muscular hypotony and failure to thrive should alert the physician to a possible diagnosis of a hereditary organic aciduria. Gas chromatography-mass spectrometry of urinary organics acids, in the present case, established the diagnosis. On autopsy, spongy degenerations were found in CNS.

During an acute respiratory infection, a 4-year-old girl with propionic acidaemia deteriorated rapidly, becoming comatose with a marked acidosis. She did not respond to standard treatment but during haemodialysis her clinical state quickly improved.

In addition to N-isovalerylglycin, isovaleric, 3-hydroxyisovaleric and methylsuccinic acids the excretion of previously unreported 4-hydroxyisovaleric acid in isovaleric acidemia is described. The new metabolite seems to be an intermediate product in the formation of methylsuccinic acid from isovaleric acid by omega-oxidation.

3-Methylglutaconic aciduria has been found in two distinct syndromes. In one there is deficient activity of 3-methylglutaconyl coenzyme A hydratase, and the only clinical manifestation observed has been retardation of speech development. In the other, which includes a majority of the patients studied, we document that the activity of this enzyme in fibroblast extracts is normal. The phenotype of this disorder is one of profound neurological impairment with retarded psychomotor development, hypotonicity and/or spasticity, convulsions or EEG abnormalities, and sensorineural changes in the eye and ear.

A girl suffering from marked muscular hypotonia, severe statomotor and mental retardation, bilateral optic atrophy with chorioretinal degeneration, convulsions and a moderate compensated metabolic acidosis is described. Screening for metabolic disorders revealed massive 3-methylglutaconic with 3-methylglutaric aciduria leading to the tentative diagnosis of 3-methylglutaconyl-CoA hydratase deficiency. Metabolite excretion was correlated with variation of leucine intake. 3-methyl-3-hydroxyglutaryl-CoA lyase activity in cultured fibroblasts was normal. The suspected metabolic defect was not demonstrable in cultured skin fibroblasts, however.

lsovaleric acidemia, a recessively inherited defect in the degradation pathway of leucine, is caused by a deficiency of isovaleryl-CoA dehydrogenase activity [l]. Accumulating isovaleryl-CoA is either hydrolyzed and excreted as isovaleric acid in the urine or further metabolized to give mainly N-isovalerylglycine and, in some cases during attacks of ketoacidosis, 3-hydroxyisova~eric f2], 4-hydroxyisovaleric [3] and methylsuccinic acids [4,5] additionally.

We report identification of short-chain acyl-CoA dehydrogenase (SCAD) deficiency in a 12-year-old boy who suffered from recurrent attacks of vomiting once or twice a year from infancy. Growth and development were normal and there were no muscular symptoms. Metabolic screening was performed during a hospitalization at 8 years of age and revealed an increased excretion of ethylmalonic acid (EMA; 45-80 mmol/mol creatinine, normal 0.2-6.6), suggesting a degradation defect of short-chain fatty acids. An increased n-butyrylcarnitine was found in freshly collected serum (0.9 micromol/L; normal0.4) but not in dry blood spots. Neither of the frequent SCAD gene variants 625GA and 511CT was present, but direct sequencing of the promoter and coding regions of the SCAD gene revealed that the patient had mutations on both alleles: 417GC (Trpl15Cys) and 1095GT (Gln341His). Neither mutation has been described before in compound heterozygosity or homozygosity. Enzymatic investigations subsequently confirmed a defect of SCAD in both fibroblasts and muscle extracts. Furthermore, expression studies of both mutations demonstrated impaired enzyme function or structure. To our knowledge, this case is the first description of a patient with proven SCAD deficiency presenting with recurrent emesis but without other symptoms, and emphasizes the wide clinical phenotype of this disorder.

Objective. Mevalonic aciduria is a consequence of the deficiency of mevalonate kinase, the first enzyme after 3-hydroxy-3-methylglutaryl-coenzyme A reductase in the biosynthesis of cholesterol and nonsterol isoprenes. To establish the clinical and biochemical phenotype of mevalonic aciduria, the authors assembled their experience with 11 patients including attempts at therapeutic interventions. Methods. Mevalonic acid in body fluids was determined by stable isotope dilution gas chromatography/mass spectroscopy with selected ion monitoring, ubiquinone-10 concentrations by reversed-phase high-pressure liquid chromatography. Results. Varying degrees of severity of clinical illness were observed despite uniform, virtual absence of residual activity of the enzyme. The most severely affected patients have had profound developmental delay, dysmorphic features, cataracts, hepatosplenomegaly, lymphadenopathy, and anemia, as well as diarrhea and malabsorption, and have died in infancy. Less severely affected patients have had psychomotor retardation, hypotonia, myopathy, and ataxia. All patients have had recurrent crises in which there was fever, lymphadenopathy, increase in size of liver and spleen, arthralgia, edema, and a morbilliform rash. Neuroimaging studies revealed selective and progressive atrophy of the cerebellum. Mevalonic acid concentrations were found to be grossly elevated in body fluids of all patients. Concentrations of plasma cholesterol were normal or only slightly reduced. Concentrations of ubiquinone-10 in plasma were found to be decreased in most patients. Abnormalities such as hypoglycemia, metabolic acidosis, or lactic acidemia, the usual concomitants of disorders of organic acid metabolism, were conspicuously absent. Conclusions. These observations establish the broad range of clinical symptoms and biochemical findings in mevalonic aciduria. It is concluded that although patients with mevalonic aciduria have a recognizable phenotype of serious clinical manifestations, some patients are likely to remain undiagnosed and may be found in a variety of subspeciality clinics, including neurology, troenterology, cardiology, and genetics.