Decreased oxidative phosphorylation and PGAM deficiency in horses suffering from atypical myopathy associated with acquired MADD

Earlier research on ten horses suffering from the frequently fatal disorder atypical myopathy showed that MADD (multiple acyl-CoA dehydrogenase deficiency) is the biochemical derangement behind atypical myopathy. From five horses that died as a result of this disease and seven healthy control horses, urine and plasma were collected ante mortem and muscle biopsies were obtained immediately post-mortem (2 patients and 7 control horses), to analyse creatine, purine and carbohydrate metabolism as well as oxidative phosphorylation. In patients, the mean creatine concentration in urine was increased 17-fold and the concentration of uric acid approximately 4-fold, compared to controls. The highest degree of depletion of glycogen was observed in the patient with the most severe myopathy clinically. In this patient, glycolysis was more active than in the other patients and controls, which may explain this depletion. One patient demonstrated very low phosphoglycerate mutase (PGAM) activity, less than 10% of reference values. Most respiratory chain complex activity in patients was 20-30% lower than in control horses, complex II activity was 42% lower than normal, and one patient had severely decrease ATP-synthase activity, more than 60% lower than in control horses. General markers for myopathic damage are creatine kinase (CK) and lactic acid in plasma, and creatine and uric acid in urine. To obtain more information about the cause of the myopathy analysis of carbohydrate, lipid and protein metabolism as well as oxidative phosphorylation is advised. This study expands the diagnostic possibilities of equine myopathies.

Expanding the clinical spectrum of 3-phosphoglycerate dehydrogenase deficiency

3-Phosphoglycerate dehydrogenase (3-PGDH) deficiency is considered to be a rare cause of congenital microcephaly, infantile onset of intractable seizures and severe psychomotor retardation. Here, we report for the first time a very mild form of genetically confirmed 3-PGDH deficiency in two siblings with juvenile onset of absence seizures and mild developmental delay. Amino acid analysis showed serine values in CSF and plasma identical to what is observed in the severe infantile form. Both patients responded favourably to relatively low dosages of serine supplementation with cessation of seizures, normalisation of their EEG abnormalities and improvement of well-being and behaviour. These cases illustrate that 3-PGDH deficiency can present with mild symptoms and should be considered as a treatable disorder in the differential diagnosis of mild developmental delay and seizures.

SYNOPSIS

we present a novel mild phenotype in patients with 3-PGDH deficiency.

Equine acquired multiple acyl-CoA dehydrogenase deficiency (MADD) in 14 horses associated with ingestion of Maple leaves (Acer pseudoplatanus) covered with European tar spot (Rhytisma acerinum)

This case-series describes fourteen horses suspected of equine acquired multiple acyl-CoA dehydrogenase deficiency (MADD) also known as atypical myopathy of which seven cases were confirmed biochemically with all horses having had access to leaves of the Maple tree (Acer pseudoplatanus) covered with European tar spot (Rhytisma acerinum). Assessment of organic acids, glycine conjugates, and acylcarnitines in urine was regarded as gold standard in the biochemical diagnosis of equine acquired multiple acyl-CoA dehydrogenase deficiency.

Amino acid profile during exercise and training in Standardbreds

The objective of this study is to assess the influence of acute exercise, training and intensified training on the plasma amino acid profile. In a 32-week longitudinal study using 10 Standardbred horses, training was divided into four phases, including a phase of intensified training for five horses. At the end of each phase, a standardized exercise test, SET, was performed. Plasma amino acid concentrations before and after each SET were measured. Training significantly reduced mean plasma aspartic acid concentration, whereas exercise significantly increased the plasma concentrations of alanine, taurine, methionine, leucine, tyrosine and phenylalanine and reduced the plasma concentrations of glycine, ornithine, glutamine, citrulline and serine. Normally and intensified trained horses differed not significantly. It is concluded that amino acids should not be regarded as limiting training performance in Standardbreds except for aspartic acid which is the most likely candidate for supplementation.

Acquired multiple Acyl-CoA dehydrogenase deficiency in 10 horses with atypical myopathy

The aim of the current study was to assess lipid metabolism in horses with atypical myopathy. Urine samples from 10 cases were subjected to analysis of organic acids, glycine conjugates, and acylcarnitines revealing increased mean excretion of lactic acid, ethylmalonic acid, 2-methylsuccinic acid, butyrylglycine, (iso)valerylglycine, hexanoylglycine, free carnitine, C2-, C3-, C4-, C5-, C6-, C8-, C8:1-, C10:1-, and C10:2-carnitine as compared with 15 control horses (12 healthy and three with acute myopathy due to other causes). Analysis of plasma revealed similar results for these predominantly short-chain acylcarnitines. Furthermore, measurement of dehydrogenase activities in lateral vastus muscle from one horse with atypical myopathy indeed showed deficiencies of short-chain acyl-CoA dehydrogenase (0.66 as compared with 2.27 and 2.48 in two controls), medium-chain acyl-CoA dehydrogenase (0.36 as compared with 4.31 and 4.82 in two controls) and isovaleryl-CoA dehydrogenase (0.74 as compared with 1.43 and 1.61 nmol min(-1) mg(-1) in two controls). A deficiency of several mitochondrial dehydrogenases that utilize flavin adenine dinucleotide as cofactor including the acyl-CoA dehydrogenases of fatty acid beta-oxidation, and enzymes that degrade the CoA-esters of glutaric acid, isovaleric acid, 2-methylbutyric acid, isobutyric acid, and sarcosine was suspected in 10 out of 10 cases as the possible etiology for a highly fatal and prevalent toxic equine muscle disease similar to the combined metabolic derangements seen in human multiple acyl-CoA dehydrogenase deficiency also known as glutaric acidemia type II.

Equine biochemical multiple acyl-CoA dehydrogenase deficiency (MADD) as a cause of rhabdomyolysis

Two horses (a 7-year-old Groninger warmblood gelding and a six-month-old Trakehner mare) with pathologically confirmed rhabdomyolysis were diagnosed as suffering from multiple acyl-CoA dehydrogenase deficiency (MADD). This disorder has not been recognised in animals before. Clinical signs of both horses were a stiff, insecure gait, myoglobinuria, and finally recumbency. Urine, plasma, and muscle tissues were investigated. Analysis of plasma showed hyperglycemia, lactic acidemia, increased activity of muscle enzymes (ASAT, LDH, CK), and impaired kidney function (increased urea and creatinine). The most remarkable findings of organic acids in urine of both horses were increased lactic acid, ethylmalonic acid (EMA), 2-methylsuccinic acid, butyrylglycine (iso)valerylglycine, and hexanoylglycine. EMA was also increased in plasma of both animals. Furthermore, the profile of acylcarnitines in plasma from both animals showed a substantial elevation of C4-, C5-, C6-, C8-, and C5-DC-carnitine. Concentrations of acylcarnitines in urine of both animals revealed increased excretions of C2-, C3-, C4-, C5-, C6-, C5-OH-, C8-, C10:1-, C10-, and C5-DC-carnitine. In addition, concentrations of free carnitine were also increased. Quantitative biochemical measurement of enzyme activities in muscle tissue showed deficiencies of short-chain acyl-CoA dehydrogenase (SCAD), medium-chain acyl-CoA dehydrogenase (MCAD), and isovaleryl-CoA dehydrogenase (IVD) also indicating MADD. Histology revealed extensive rhabdomyolysis with microvesicular lipidosis predominantly in type 1 muscle fibers and mitochondrial damage. However, the ETF and ETF-QO activities were within normal limits indicating the metabolic disorder to be acquired rather than inherited. To our knowledge, these are the first cases of biochemical MADD reported in equine medicine.

Equine metabolic myopathies with emphasis on the diagnostic approach comparison with human myopathies A review

This review gives an overview of the presently known human and equine metabolic myopathies with emphasis on the diagnostic approach. Metabolic myopathies are muscle disorders caused by a biochemical defect of the skeletal muscle energy system, which results in inefficient muscle performance. Myopathies can arise in different levels of the metabolic system. In this review the metabolic myopathies are categorized in disorders of the carbohydrate metabolism, lipid metabolism, mitochondrial myopathies (other than those described in lipid metabolism), disorders of purine metabolism, primary disorders involving ion channels and electrolyte flux and secondary or acquired metabolic myopathies.

Removal of chloroform from biodegradable therapeutic microspheres by radiolysis

Radioactive holmium-166 loaded poly(l-lactic acid) microspheres are promising systems for the treatment of liver malignancies. These microspheres are loaded with holmium acetylacetonate (HoAcAc) and prepared by a solvent evaporation method using chloroform. After preparation the microspheres (Ho-PLLA-MS) are activated by neutron irradiation in a nuclear reactor. It was observed that relatively large amounts of residual chloroform (1000-6000 ppm) remained in the microspheres before neutron irradiation. Since it is known that chloroform is susceptible for high-energy radiation, we investigated whether neutron and gamma irradiation could result in the removal of residual chloroform in HoAcAc-loaded and placebo PLLA-MS by radiolysis. To investigate this, microspheres with relatively high and low amounts of residual chloroform were subjected to irradiation. The effect of irradiation on the residual chloroform levels as well as other microsphere characteristics (morphology, size, crystallinity, molecular weight of PLLA and degradation products) were evaluated. No chloroform in the microspheres could be detected after neutron irradiation. This was also seen for gamma irradiation at a dose of 200 kGy phosgene, which can be formed as the result of radiolysis of chloroform, was not detected with gas chromatography-mass spectrometry (GC-MS). A precipitation titration showed that radiolysis of chloroform resulted in the formation of chloride. Gel permeation chromatography and differential scanning calorimetry showed a decrease in molecular weight of PLLA and crystallinity, respectively. However, no differences were observed between irradiated microsphere samples with high and low initial amounts of chloroform. In conclusion, this study demonstrates that neutron and gamma irradiation results in the removal of residual chloroform in PLLA-microspheres.

Prolonged exercise testing in two children with a mild Multiple Acyl-CoA-Dehydrogenase deficiency

BACKGROUND: Multiple Acyl-CoA-Dehydrogenase deficiency (MADD) is an inherited metabolic disorder characterized by impaired oxidation of fatty acids and some amino acids. METHODS: We were interested whether children with MADD could tolerate a prolonged low-intensity exercise test and if this test could have any additional diagnostic value. Therefore, we performed a maximal exercise test and a low-intensity prolonged exercise test in 2 patients with MADD and in 5 control subjects. During a prolonged exercise test the subjects exercised on a cycle ergometer at a constant workload of 30% of their maximum for 90 minutes and heart rate, oxygen uptake, fuel utilization and changes in relevant blood and urinary parameters were monitored. RESULTS: The tests were tolerated well. During the prolonged exercise test the fatty acid oxidation (FAO) was quite low compared to 5 control subjects, while characteristic metabolites of MADD appeared in plasma and urine. CONCLUSION: We suggest that the prolonged exercise test could be of diagnostic importance and might replace the fasting test as a diagnostic procedure in some cases, particularly in patients with anamnestic signs of intolerance for prolonged exercise.

Rhabdomyolysis in early-onset very long-chain acyl-CoA dehydrogenase deficiency despite normal glucose after fasting

A patient with very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency presented in the neonatal period with hypoketotic hypoglycaemia and at the age of 1 year with rhabdomyolysis and normal glucose after fasting. Rhabdomyolysis may occur in the absence of hypoglycaemia in young infants as well as in older patients.

Ornithine aminotransferase deficiency: diagnostic difficulties in neonatal presentation

We describe two unrelated cases of ornithine aminotransferase (OAT) deficiency with rare neonatal presentation of hyperammonaemia. The diagnosis in the neonatal presentation of OAT deficiency is hampered as hyperornithinaemia is absent. Enzyme and mutation studies confirmed the diagnosis. OAT deficiency should be included in differential diagnosis of neonatal hyperammonaemia.

Prenatal and early postnatal treatment in 3-phosphoglycerate-dehydrogenase deficiency

3-phosphoglycerate-dehydrogenase (3-PGDH) deficiency is an L-serine biosynthesis disorder, characterised by congenital microcephaly, severe psychomotor retardation, and intractable seizures. We report prenatal diagnosis of an affected fetus by DNA mutation analysis. Ultrasound assessment showed a reduction in fetal head circumference from the 75th percentile at 20 weeks' gestation to the 29th percentile at 26 weeks. L-serine was then given to the mother, which resulted in an enlarged fetal head circumference to the 76th percentile at 31 weeks. At birth, the girl's head circumference was normal, and at 48 months' follow-up, her psychomotor development has been unremarkable. 3-PGDH deficiency is an inborn metabolic error that can be successfully treated antenatally.

Mitochondrial respiratory chain disease presenting as progressive bulbar paralysis of childhood

We report two siblings with a mitochondrial respiratory chain defect who presented with progressive bulbar paralysis of childhood (Fazio-Londe disease). Mitochondrial respiratory chain defects should be considered in differential diagnosis of this rare clinical entity.

Glutathione synthetase deficiency associated with antenatal cerebral bleeding

We present a newborn with glutathione synthetase deficiency and intracranial haemorrhages. Because the latter are rare in term newborns a possible relationship with glutathione synthetase deficiency will be discussed.

Energy expenditure in patients with propionic and methylmalonic acidaemias

Resting energy expenditure (REE) was investigated in 8 children with propionic and methylmalonic acidaemias because a lowered REE has been reported in the literature. We observed a marginally elevated REE and think that adequate caloric intake and the use of a synthetic amino acid mixture are responsible for this.

Plasma pipecolic acid is frequently elevated in non-peroxisomal disease

We reviewed our data on patients in whom plasma pipecolic acid was analysed. Mild to moderate elevations of pipecolic acid were frequently found in non-peroxisomal disorders and this should be taken into account when interpreting the laboratory data.

Glutaric aciduria type III: a distinctive non-disease?

Glutaric aciduria type III is a rare metabolic abnormality leading to persistent isolated glutaric acid excretion. We report the clinical and biochemical phenotypes of three affected children. The first patient is a boy with dysmorphic features and a chromosomal deletion (monosomy 6q26-qter) in whom a persistent glutaric aciduria (500 mmol/mol creatinine, normal <10) was detected during a routine metabolic investigation. The second boy suffered from acute gastroenteritis and hyperthyroidism, when an excessively high urinary glutaric acid excretion was identified (1460 mmol/mol creatinine). The third patient is a girl with constantly elevated glutaric acid in her urine (290 mmol/mol creatinine) but no symptoms of significant disease. In all our patients, glutaric aciduria type I (glutaryl-CoA dehydrogenase deficiency), glutaric aciduria type II (multiple acyl-CoA dehydrogenation defect), and secondary forms of glutaric aciduria (for example due to intestinal infections or mitochondrial dysfunction) could be excluded. Loading with the precursor amino acid lysine in all patients as well as with pipecolic acid in the third case led to an increase in urinary glutaric acid excretion, proving the endogenous origin of glutarate. Glutaric aciduria type III (a defect reported to be caused by peroxisomal glutaryl-CoA oxidase deficiency) is our presumptive diagnosis. However, peroxisomal glutaryl-CoA oxidase is not well characterized and no reliable approach for the direct determination of this enzyme is available to us. To our knowledge, in the English language literature only a single patient with glutaric aciduria type III has been described. Our cases reported here confirm the earlier assumption that glutaric aciduria type III is not related to a distinctive phenotype. Glutaric aciduria type III appears to be a rare metabolic abnormality, presumably of peroxisomal metabolism. However, its pathophysiological impact still needs further investigation.

Congenital microcephaly and seizures due to 3-phosphoglycerate dehydrogenase deficiency: outcome of treatment with amino acids

Congenital microcephaly, intractable seizures and severe psychomotor retardation characterize 3-phosphoglycerate dehydrogenase (3-PGDH) deficiency, a disorder of L-serine biosynthesis. The enzyme defect results in low concentrations of serine and to a variable degree of glycine in plasma and cerebrospinal fluid. Short-term beneficial effects have been reported of oral treatment with the deficient amino acids. In this paper, we report the first follow-up data of amino acid therapy in five patients treated for 3-7.5 years. Different treatment regimes were used, but a favourable response to amino acids was observed in all patients. A major reduction in seizure frequency occurred in all patients; two patients became free of seizures. Amino acids were well tolerated and no adverse effects were documented. A progress of psychomotor development was only observed in one patient, diagnosed early and treated with a high dosage of L-serine. A favourable outcome of 3-PGDH deficiency depends on early diagnosis and treatment.

Increased urinary leukotriene E(4) during febrile attacks in the hyperimmunoglobulinaemia D and periodic fever syndrome

BACKGROUND

The hyperimmunoglobulinaemia D and periodic fever syndrome is a hereditary periodic fever, caused by deficiency of the enzyme mevalonate kinase. It is unclear how this defect leads to recurrent fever episodes.

AIM

To assess the involvement of cysteinyl leukotrienes in the pathogenesis of fever attacks as reflected by urinary leukotriene E(4) (LTE(4)) excretion.

METHODS

Urinary LTE(4) was measured in seven patients while febrile and afebrile.

RESULTS

LTE(4) was raised during fever in all subjects (46-199 nmol/mol creatinine, mean 92; normal <40). Urinary LTE(4) was normal between attacks, as well as in normal children with fever as a result of miscellaneous causes.

CONCLUSION

Our results suggest that cysteinyl leukotrienes play a role in the pathophysiology of this disorder. As no effective treatment is yet available, leukotriene receptor antagonists might offer a new therapeutic approach for patients with the hyperimmunoglobulinaemia D and periodic fever syndrome.

Tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency in Dutch neonates

Four neonates with a positive phenylalanine screening test (Phe concentrations between 258 and 1250 micromol/L) were investigated further to differentiate between phenylalanine hydroxylase (PAH) deficiency and variant hyperphenylalaninaemia (HPA) forms. In patients 1 and 2 a tetrahydrobiopterin (BH4) load caused a significant decrease of the plasma Phe levels. A combined phenylalanine/BH4 loading test was performed in patients 2, 3 and 4. In the latter two patients, plasma Phe concentrations completely normalized within 8 h after the BH4 load (20 mg/kg). Basal urinary pterins were normal in all four patients. The activity of dihydropteridine reductase (DHPR) was normal in patients 1, 2 and 3 and 50% of control values in patient 4 (not in the range of DHPR-deficient patients). In patient 3 a subsequent phenylalanine loading test with concomitant analysis of plasma biopterins revealed a normal increase of biopterin, excluding a BH4 biosynthesis defect. Pterins and neurotransmitter metabolites in CSF of patients 1, 3 and 4 were normal. DNA mutations detected in the PAH gene of patients 1-4 were A313T, and L367fsinsC; V190A and R243X; A300S and A403V; R241C and A403V. The results are suggestive for mutant PAH enzymes with decreased affinity for the cofactor BH4.

Genomic organization of the human phosphomannose isomerase (MPI) gene and mutation analysis in patients with congenital disorders of glycosylation type Ib (CDG-Ib)

CDG-Ib is the "gastro-intestinal" type of the congenital disorders of glycosylation (CDG) and a potentially treatable disorder. It has been described in patients presenting with congenital hepatic fibrosis and protein losing enteropathy. The symptoms result from hypoglycosylation of serum- and other glycoproteins. CDG-Ib is caused by a deficiency of mannose-6-phosphate isomerase (synonym: phosphomannose isomerase, EC 5.3.1.8), due to mutations in the MPI gene. We determined the genomic structure of the MPI gene in order to simplify mutation detection. The gene is composed of 8 exons and spans only 5 kb. Eight (7 novel) different mutations were found in seven patients with a confirmed phosphomannose isomerase deficiency, analyzed in the context of this study: six missense mutations, a splice mutation and one insertion. In the last, the mutation resulted in an unstable transcript, and was hardly detectable at the mRNA level. This emphasizes the importance of mutation analysis at the genomic DNA level.

Carnitine-acylcarnitine translocase deficiency: metabolic consequences of an impaired mitochondrial carnitine cycle

We describe a patient with carnitine-acylcarnitine translocase deficiency (MIM 212138), who presented with neonatal generalized seizures, heart failure, and coma. Laboratory evaluation revealed hypoglycemia, hyperammonemia, lactic acidemia, hyperuricemia, and mild dicarboxylic aciduria. The fact that total plasma carnitine (7.1 micromol/l [20-30]) and free carnitine (1.9 micromol/l [12-18]) were low together with a high acylcarnitine/free carnitine ratio of 2.7 [0.4-1.0] prompted acylcarnitine analysis. This revealed the presence of large amounts of long-chain derivatives including C(16:0), C(16:1), C(18:1), C(18:2). Based on these findings carnitine-acylcarnitine translocase deficiency was suspected which was confirmed by enzyme studies in fibroblasts. The underlying complex metabolic consequences of this defect are reviewed. Prenatal diagnosis was performed in a subsequent pregnancy and a defect ruled out by measurement of carnitine-acylcarnitine translocase activity in cultured chorionic villi cells. As the clinical recognition of a life-threatening fatty acid oxidation disorder may be difficult, defects in this pathway should be considered in any child with coma, an episode of a Reye-like syndrome, and cardiomyopathy. Since routine laboratory tests often do not provide clues about potential disorders and profiles of urinary organic acids may not be characteristic, we recommend to measure free carnitine and acylcarnitines in plasma in any child with hyperammonemia, hypo/hyperketotic hypoglycemia or lactic acidemia for prompt treatment, proper genetic counseling, and potential prenatal diagnosis.

Congenital hepatic fibrosis in 3 siblings with phosphomannose isomerase deficiency

Congenital hepatic fibrosis is a rare disorder of intrahepatic bile ducts with the persistence of embryological bile duct structures in ductal plate configuration. Three siblings aged 18, 17 and 14 years old were found to have congenital hepatic fibrosis associated with a deficiency of the enzyme phosphomannose isomerase. The clinical symptoms were recurrent attacks of persistent vomiting with diarrhea and mild hepatomegaly. The biochemical abnormalities included elevated serum transferases during attacks, clotting factor deficiencies and persistent hypoalbuminemia. In the youngest patient protein-losing enteropathy was present. Liver biopsies of the three patients taken when they were 1, 3 and 14 years old showed an excess of bile duct structures in ductal plate configuration with mild fibrosis in the portal triads. In one patient the liver biopsy was repeated after 18 years and showed only a mild progression of fibrosis in the portal triads. Duodenal biopsies taken in infancy in two of the three patients did not show any abnormalities. Recognition of phosphomannose isomerase deficiency in association with congenital hepatic fibrosis and protein-losing enteropathy is important, because some of the clinical symptoms are potentially treatable by oral mannose therapy.

Mutations in MVK, encoding mevalonate kinase, cause hyperimmunoglobulinaemia D and periodic fever syndrome

Hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS; MIM 260920) is an autosomal recessive disorder characterized by recurrent episodes of fever associated with lymphadenopathy, arthralgia, gastrointestinal dismay and skin rash. Diagnostic hallmark of HIDS is a constitutively elevated level of serum immunoglobulin D (IgD), although patients have been reported with normal IgD levels. To determine the underlying defect in HIDS, we analysed urine of several patients and discovered increased concentrations of mevalonic acid during severe episodes of fever, but not between crises. Subsequent analysis of cells from four unrelated HIDS patients revealed reduced activities of mevalonate kinase (MK; encoded by the gene MVK), a key enzyme of isoprenoid biosynthesis. Sequence analysis of MVK cDNA from the patients identified three different mutations, one of which was common to all patients. Expression of the mutant cDNAs in Escherichia coli showed that all three mutations affect the activity of the encoded proteins. Moreover, immunoblot analysis demonstrated a deficiency of MK protein in patient fibroblasts, indicating a protein-destabilizing effect of the mutations.

Smith-Lemli-Opitz syndrome is caused by mutations in the 7-dehydrocholesterol reductase gene

Smith-Lemli-Opitz syndrome is a frequently occurring autosomal recessive developmental disorder characterized by facial dysmorphisms, mental retardation, and multiple congenital anomalies. Biochemically, the disorder is caused by deficient activity of 7-dehydrocholesterol reductase, which catalyzes the final step in the cholesterol-biosynthesis pathway-that is, the reduction of the Delta7 double bond of 7-dehydrocholesterol to produce cholesterol. We identified a partial transcript coding for human 7-dehydrocholesterol reductase by searching the database of expressed sequence tags with the amino acid sequence for the Arabidopsis thaliana sterol Delta7-reductase and isolated the remaining 5' sequence by the "rapid amplification of cDNA ends" method, or 5'-RACE. The cDNA has an open reading frame of 1,425 bp coding for a polypeptide of 475 amino acids with a calculated molecular weight of 54.5 kD. Heterologous expression of the cDNA in the yeast Saccharomyces cerevisiae confirmed that it codes for 7-dehydrocholesterol reductase. Chromosomal mapping experiments localized the gene to chromosome 11q13. Sequence analysis of fibroblast 7-dehydrocholesterol reductase cDNA from three patients with Smith-Lemli-Opitz syndrome revealed distinct mutations, including a 134-bp insertion and three different point mutations, each of which was heterozygous in cDNA from the respective parents. Our data demonstrate that Smith-Lemli-Opitz syndrome is caused by mutations in the gene coding for 7-dehydrocholesterol reductase.

Beneficial effects of L-serine and glycine in the management of seizures in 3-phosphoglycerate dehydrogenase deficiency

3-Phosphoglycerate dehydrogenase (3-PGDH) deficiency is an inborn error of serine biosynthesis. Patients are affected with congenital microcephaly, psychomotor retardation, and intractable seizures. The effects of oral treatment with amino acids were investigated in 2 siblings. L-Serine up to 500 mg/kg/day was not sufficient for seizure control. Addition of glycine 200 mg/kg/day resulted in complete disappearance of seizures. Electroencephalographic abnormalities gradually resolved after 6 months. We conclude that 3-PGDH can be treated effectively by a combination of L-serine and glycine.

The effect of fasting, long-chain triglyceride load and carnitine load on plasma long-chain acylcarnitine levels in mitochondrial very long-chain acyl-CoA dehydrogenase deficiency

We studied a 10-year-old patient with very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency who was originally (mis)diagnosed as having systemic carnitine deficiency. He was subjected to a fasting test, a long-chain triglyceride (LCT) loading test (1.5 g/kg) and an intravenous carnitine clearance test (0.25 mumol/kg per min). Plasma acylcarnitines were analysed using a quantitative GC-CI-MS method. During fasting, all long-chain acylcarnitines with a chain length of C14 and higher (especially C14:1) increased dramatically. Total plasma long-chain acylcarnitine reached a concentration of 28.6 mumol/L. LCT loading resulted in a moderate increase, mainly of the C18 esters. The carnitine infusion, which led to a supranormal plasma free carnitine concentration, gave only a slight but generalized rise of long-chain acylcarnitines. Although only one patient could be tested, the results suggest that the accumulation of potentially toxic long-chain acylcarnitines in VLCAD deficiency is provoked by fasting, LCT loading and carnitine supplementation. Therapy should be adjusted accordingly.

A novel disorder of N-glycosylation due to phosphomannose isomerase deficiency

Three siblings suffered from an unusual disorder of cyclic vomiting and congenital hepatic fibrosis. Serum transferrin isoelectric focusing showed increased asialo- and disialotransferrin isoforms as seen in the carbohydrate-deficient glycoprotein (CDG) syndrome type I. Phosphomannomutase, which is deficient in most patients with type I CDG syndrome, was found to be normal in all three patients. Structural analysis of serum transferrin revealed nonglycosylated, hypoglycosylated, and normoglycosylated transferrin molecules. These findings suggested a defect in the early glycosylation pathway. Phosphomannose isomerase was found to be deficient and the defect was present in leucocytes, fibroblasts, and liver tissue. Phosphomannose isomerase deficiency appears to be a novel glycosylation disorder, which is biochemically indistinguishable from CDG syndrome type I. However, the clinical presentation is entirely different.

Simultaneous analysis of plasma free fatty acids and their 3-hydroxy analogs in fatty acid beta-oxidation disorders

We present a new derivatization procedure for the simultaneous gas chromatographic-mass spectrometric analysis of free fatty acids and 3-hydroxyfatty acids in plasma. Derivatization of target compounds involved trifluoroacetylation of hydroxyl groups and tert-butyldimethylsilylation of the carboxyl groups. This new derivatization procedure had the advantage of allowing the complete baseline separation of free fatty acids and 3-hydroxyfatty acids while the superior gas chromatographic and mass spectrometric properties of tert-butyldimethylsilyl derivatives remained unchanged, permitting a sensitive analysis of the target compounds. Thirty-nine plasma samples from control subjects and patients with known defects of mitochondrial fatty acid beta-oxidation were analyzed. A characteristic increase of long-chain 3-hydroxyfatty acids was observed for all of the long-chain 3-hydroxyacyl-CoA dehydrogenase-deficient and mitochondrial trifunctional protein-deficient plasma samples. For medium-chain acyl-CoA dehydrogenase deficiency and very-long-chain acyl-CoA dehydrogenase deficiency, decenoic and tetradecenoic acids, respectively, were the main abnormal fatty acids, whereas the multiple acyl-CoA dehydrogenase-deficient patients showed variable increases of these unusual intermediates. The results showed that this selective and sensitive method is a powerful tool in the diagnosis and monitoring of mitochondrial fatty acid beta-oxidation disorders.

Inherited defects of purine and pyrimidine metabolism: laboratory methods for diagnosis

The diagnosis of the majority of the known inherited defects of purine and pyrimidine metabolism can be achieved by analysing urinary excretion profiles. A quantitative measurement of the urinary uric acid/creatinine ratio should be the first approach for purine defects. The general screening system involves separation of the bases and nucleosides by reversed-phase high-performance liquid chromatography and multiwavelength UV detection. The catabolic defects of pyrimidine degradation can be diagnosed by gas chromatography-mass spectrometry as used for organic acids. For the detection of adenylosuccinase deficiency, several simple but effective thin-layer chromatographic methods are available. Techniques such as liquid chromatography-mass spectrometry, direct nega-tiveion fast-atom bombardment mass spectrometry, and proton nuclear magnetic resonance spectroscopy give promising results, but are not yet being used on a large scale. Patients should keep to a simple diet and preferably be free of medication in order to allow a reliable interpretation of the analytical data.

Asymptomatic and late-onset ornithine transcarbamylase deficiency caused by a A208T mutation: clinical, biochemical and DNA analyses in a four-generation family

We describe a 4-generation family in which a previously healthy 10-year-old boy died of late-onset ornithine transcarbamylase (OTC) deficiency. Pedigree analysis and allopurinol loading tests in female relatives were not informative. A missense mutation (A208T) in the OTC gene was detected in the deceased patient and in several clinically healthy male and female relatives, the oldest male being 97 years old. OTC deficiency was established in autopsy liver tissue of the propositus and liver biopsy samples of his sister, mother, and a maternal uncle. The males had 4% and 6% residual activity, respectively, the females 58% and 67%, respectively. The observed relation between the mutation and the decreased OTC activity in liver tissue of these subjects suggests that the mutation is a deleterious one. Late-onset, "mild" OTC deficiency can have a fatal or a favorable outcome. The disease can segregate undetected in families.

Quantitative analysis of plasma acylcarnitines using gas chromatography chemical ionization mass fragmentography

A stable isotope dilution gas chromatography chemical ionization mass spectrometry (GC-CI-MS) method was developed for the quantitative profiling of plasma acylcarnitines. The clean-up procedure was comprised of a solid-phase cation exchange extraction using PRS-columns from which the acylcarnitines were eluted with a barium chloride solution. Isolated acylcarnitines were transformed into acyloxylactones and analyzed by positive GC-CI-MS using isobutane as reactant gas. The selected monitoring of a common ion at m/z [85]+ and the protonated molecular ion enabled a selective and sensitive detection of all C2-C18 acylcarnitines. An accurate quantitation was achieved by the use of stable isotope-labeled internal standards (C2-C18) and acylcarnitines could be analyzed in the sub-nanomolar range. Control values for C2-C18 acylcarnitines in plasma were established. Concentrations ranged from 0.02 micromol/L for C14-acylcarnitine to 4.90 micromol/L for C2-acylcarnitine. The diagnostic suitability of the method was demonstrated for patients with medium-chain acyl-CoA dehydrogenase deficiency and very long-chain acyl-CoA dehydrogenase deficiency.

Magnetic resonance imaging and spectroscopy of the brain in propionic acidemia: clinical and biochemical considerations

Three patients with propionic acidemia were studied. The first patient was diagnosed at the age of 9 mo, 3 mo after he developed hypotonia and choreoathetoid movements after an upper respiratory tract infection. The second patient was diagnosed at the age of 1.5 mo when she became comatose after nasogastric tube feeding because of failure to thrive. The third patient was diagnosed at the age of 5 d when she presented with feeding difficulties, hypotonia, and respiratory insufficiency. Magnetic resonance imaging (MRI) of the brain in all patients revealed delayed myelination and some cerebral atrophy. In the patient with choreoathetosis, MRI showed bilateral abnormalities in the signal intensity of the putamen and caudate nuclei. MRI of the other two patients showed normal basal ganglia. Proton magnetic resonance spectroscopy (1H MRS) from a voxel located in the basal ganglia revealed a decrease in N-acetylaspartate and myo-inositol peaks and an elevation of glutamine/ glutamate. The presence of spectroscopic abnormalities in a stable metabolic condition, in particular the rise in glutamine/ glutamate, indicates that the metabolic balance on cerebral parenchymal level is less optimal than estimated from biochemical analysis of urine, plasma, or cerebrospinal fluid.

3-, 6- and 7-hydroxyoctanoic acids are metabolites of medium-chain triglycerides and excreted in urine as glucuronides

Three new metabolites of medium-chain fatty acid oxidation, 3-, 6- and 7-hydroxyoctanoyl beta-D-glucuronide, were identified in the urine of six infants who were fed a diet enriched in medium-chain triglycerides (MCT). Glucuronides were extracted from the urine by organic solvent extraction with ethyl acetate and by solid-phase extraction on Sep-Pak C18 cartridges. The compounds of interest were also purified from the organic solvent extract by preparative one-dimensional thin-layer chromatography. Cleavage of the glucuronides was achieved by either alkaline hydrolysis or enzymatic hydrolysis with beta-D-glucuronidase. The analyses of the trimethylsilylated derivatives were performed both by gas chromatography with flame ionization detection (GC/FID) and by gas chromatography/mass spectrometry (GC/MS). The structure of the hydroxyoctanoic acids was proved by comparison of their mass spectra with those of reference substances. Authentic 6-hydroxyoctanoic acid was synthesized. The presence of 6-hydroxyoctanoyl glucuronide shows that in addition to beta-oxidation, omega-oxidation and (omega-1)-hydroxylation, medium-chain fatty acids can be oxidized at the omega-2 position. The conjugation of medium-chain hydroxy-monocarboxylic acids with glucuronic acid has not been described in humans before.

Peroxisomal disorders: a review

Until recently peroxisomal disorders were considered to be extremely rare and the diagnostic procedures available for postanatal and prenatal diagnosis were not widely known. At present, 17 human disorders are linked to peroxisomal dysfunction. The clinical, biochemical and morphological peroxisome heterogeneity described in the different diseases illustrate that only combined analysis of all the different approaches will lead to a correct diagnosis and a coherent pathophysiological model to guide ongoing research. With the study of human peroxisomal disease, advances have been gained as to the function of the peroxisome in normal and pathological conditions. Genetic analysis of peroxisome biogenesis and research on peroxisomal targeting signals are now in progress. Peroxisomal disorders are usually classified according to the degree of biochemical impairment. In this paper, a tentative classification of peroxisomal disorders will be proposed, based on the degree of biochemical abnormalities combined with new data obtained on whether or not defective peroxisome assembly is involved: (1) disorders with peroxisome assembly deficiencies; (2) disorders with single enzyme deficiencies. The clinical onset and the major symptoms of the various disorders, and the recently discovered findings are discussed.

Group tests for selective screening of inborn errors of metabolism

Selective screening for inherited metabolic disorders can be performed efficiently by chromatographic techniques. Each technique is suited for a well-defined group of substances present in urine, plasma and CSF. A comprehensive screening programme may involve the analysis of amino acids, organic acids, imidazoles, purines and pyrimidines, oligosaccharides and mucopolysaccharides in urine as well as very long-chain fatty acids in plasma. The experienced laboratory, in close co-operation with a specialized paediatrician, will make a positive diagnosis in 6% of the referred samples, provided a careful selection of the patients is made. Our experience of 10 years of screening revealed 100 different defects; 30% of these were so-called amino acid disorders, 50% organic acidurias and the remaining 20% miscellaneous defects. Chromatographic methods are well suited for the discovery of novel defects. In this respect group screening tests will remain of major importance for the study of inborn errors of metabolism.

Selective screening for amino acid disorders

The analysis of amino acids is the most frequently applied technique in the selective screening of inborn errors of metabolism. When urine is used as a starting material, simple techniques such as thin-layer chromatography or high-voltage electrophoresis is preferred as a first approach. The quantitative analysis requires instrumentation, usually an amino acid analyser. Both plasma and urine are needed for establishing renal transport defects. Apart from the accumulation of the 'usual' amino acids, the presence of unusual amino acids may be of diagnostic significance. Furthermore the finding of decreased plasma concentrations of specific amino acids may pinpoint several inherited defects. No amino acid screening procedure is complete without the availability of an organic acid and a purine/pyrimidine analytical system, both yielding important additional diagnostic information. Considerable clinical problems may occur in subjects with a decreased tolerance to protein amino acids without being homozygous for any inherited defect. Examples of these disorders that need further studies are homocysteinaemia associated with vascular disease and carriers of ornithine transcarbamylase deficiency.

Experimental design of 31P MRS assessment of human forearm muscle function: restrictions imposed by functional anatomy

The restrictions imposed by the functional anatomy of the finger flexor muscles on the experimental design of 31P MRS assessment of human forearm muscle function employing surface coil localization and voluntary exercise were investigated. It was found that 31P MRS metabolic data of finger flexor muscle should be correlated with mechanical data of combined flexion of only the ring and little fingers, rather than all four fingers as has been commonly the case in previously reported studies.