Pyridoxine responsive epilepsy caused by a novel homozygous PNPO mutation

We report a patient with anti-epileptic treatment refractory neonatal seizures responsive to pyridoxine. Biochemical analysis revealed normal markers for antiquitin deficiency and also mutation analysis of the ALDH7A1 (Antiquitin) gene was negative. Mutation analysis of the PNPO gene revealed a novel, homozygous, presumed pathogenic mutation (c.481C > T; p.(Arg161Cys)). Measurements of B6 vitamers in a CSF sample after pyridoxine administration revealed elevated pyridoxamine as the only metabolic marker for PNPO deficiency. With pyridoxine monotherapy the patient is seizure free and neurodevelopmental outcome at the age of 14 months is normal.

Perioperative hyperinsulinaemic normoglycaemic clamp causes hypolipidaemia after coronary artery surgery

BACKGROUND

Glucose-insulin-potassium (GIK) administration is advocated on the premise of preventing hyperglycaemia and hyperlipidaemia during reperfusion after cardiac interventions. Current research has focused on hyperglycaemia, largely ignoring lipids, or other substrates. The present study examines lipids and other substrates during and after on-pump coronary artery bypass grafting and how they are affected by a hyperinsulinaemic normoglycaemic clamp.

METHODS

Forty-four patients were randomized to a control group (n=21) or to a GIK group (n=23) receiving a hyperinsulinaemic normoglycaemic clamp during 26 h. Plasma levels of free fatty acid (FFA), total and lipoprotein (VLDL, HDL, and LDL)-triglycerides (TG), ketone bodies, and lactate were determined.

RESULTS

In the control group, mean FFA peaked at 0.76 (sem 0.05) mmol litre(-1) at early reperfusion and decreased to 0.3-0.5 mmol litre(-1) during the remaining part of the study. GIK decreased FFA levels to 0.38 (0.05) mmol litre(-1) at early reperfusion, and to low concentrations of 0.10 (0.01) mmol litre(-1) during the hyperinsulinaemic clamp. GIK reduced the area under the curve (AUC) for FFA by 75% and for TG by 53%. The reduction in total TG was reflected by a reduction in the VLDL (-54% AUC) and HDL (-42% AUC) fraction, but not in the LDL fraction. GIK prevented the increase in ketone bodies after reperfusion (-44 to -47% AUC), but was without effect on lactate levels.

CONCLUSIONS

Mild hyperlipidaemia was only observed during early reperfusion (before heparin reversal) and the hyperinsulinaemic normoglycaemic clamp actually resulted in hypolipidaemia during the largest part of reperfusion after cardiac surgery.

Prolidase deficiency diagnosed by 1H NMR spectroscopy of urine

Three urine samples from two prolidase-deficient patients were analysed using 1H NMR spectroscopy. One-dimensional 1H NMR spectra showed a characteristic pattern of overlapping resonances of the proline and hydroxyproline protons of the imidodipeptides. The model compounds Ala-Pro, Gly-Pro, Phe-Pro, Leu-Pro, Val-Pro, Gly-Hyp and Pro-Hyp were measured as well. The non-proline resonances of Val-Pro, Ala-Pro and Gly-Pro could be assigned in the urine spectra. These resonances could then be used for quantification of the corresponding imidodipeptids. The presence of Leu-Pro in the patients' urine was demonstrated by the results of COSY experiments. However, this imidodipeptide could not be quantified owing to overlap of the resonaces in the one-dimensional 1H NMR spectrum of the patients' urine. Phe-Pro, Pro-Hyp and Gly-Hyp could not be assigned in the spectrum of the patient's urine. The characteristic resonances in the urine from a prolidase-deficient patient, i.e. Ala-Pro, Val-Pro, Gly-Pro, and resonances of the (hydroxy)proline part of the imidodipeptides can be used to diagnose this disease.

Mild learning difficulties and offending behaviour--is there a link with monoamine oxidase A deficiency?

We have attempted to replicate the findings of Brunner et al., who described a large Dutch kindred where several males were of borderline intelligence and showed characteristically aggressive and sometimes dangerous or extremely antisocial behaviour. The genetic defect for this syndrome was assigned to the p11-p21 region of the X chromosome following linkage analysis in a single kindred. Subsequent sequencing of a candidate gene, monoamine oxidase A (MAO-A), at the position of maximum linkage revealed a causative mutation in the coding region of the MAO-A gene in position 936. In addition to identifying both the phenotype and the associated mutation found by Brunner et al., we also wished to test the hypothesis that mutations elsewhere in the MAO-A gene could cause the low intelligence quotient/personality disorder phenotype associated with low urinary catecholamine degradation products. Fifty-four male subjects similar in clinical characteristics to the affected males in the Dutch kindred were identified within secure mental health facilities in England and Wales. All were assessed using the antisocial personality disorder section of the SCID-II interview instrument, and information about their offending behaviour and family history was obtained from the medical notes. A blood and early-morning urine sample was obtained from each patient. Analysis of urinary excretion patterns of biogenic amines and their metabolites, represented as ratios of normetanefrine to vanillylmandelic acid, revealed two possible cases of MAO-A deficiency, which were found to be negative after resampling.

Human alpha-N-acetylgalactosaminidase (alpha-NAGA) deficiency: no association with neuroaxonal dystrophy?

Two new individuals with alpha-NAGA deficiency are presented. The index patient, 3 years old, has congenital cataract, slight motor retardation and secondary demyelinisation. Screening of his sibs revealed an alpha-NAGA deficiency in his 7-year-old healthy brother who had no clinical or neurological symptoms. Both sibs are homozygous for the E325K mutation, the same genotype that was found in the most severe form of alpha-NAGA deficiency presenting as infantile neuroaxonal dystrophy. Thus, at the age of 7 years the same genotype of alpha-NAGA may present as a 'non-disease' (present healthy case) and can be associated with the vegetative state (the first two patients described with alpha-NAGA deficiency). The clinical heterogeneity among the 11 known individuals with alpha-NAGA deficiency is extreme, with a 'non-disease' (two cases) and infantile neuroaxonal dystrophy (two cases) at the opposite sides of the clinical spectrum. The broad spectrum is completed by a very heterogeneous group of patients with various degrees of epilepsy/behavioural difficulties/psychomotor retardation (four patients) and a mild phenotype in adults without overt neurological manifestations who have angiokeratoma and clear vacuolisation in various cell types (three cases). These observations are difficult to reconcile with a straightforward genotype-phenotype correlation and suggest that factors or genes other than alpha-NAGA contribute to the clinical heterogeneity of the 11 patients with alpha-NAGA deficiency.

Tyrosine hydroxylase deficiency unresponsive to L-dopa treatment with unusual clinical and biochemical presentation

Tyrosine hydroxylase (TH) deficiency is generally considered as a cause of the autosomal recessive form of dopa-responsive dystonia, also known as Segawa disease. Clinical hallmarks comprise parkinsonian and other extrapyramidal symptoms. Biochemically the defect leads to the defective synthesis of catecholamines, in particular dopamine. The diagnosis relies on a characteristic pattern of biogenic amine metabolites exclusively in the CSF and can be confirmed by establishing a mutation in the TH gene. Here we present a patient meeting all diagnostic criteria, including a new homozygous mutation (926T > C) with confirmed parental heterozygosity, extrapyramidal symptoms, but atypical other symptoms with periodic neurological episodes observed every 4 days and unresponsive to dopa treatment. The CSF biochemical abnormalities were severe. Uncharacteristically, a strongly abnormal urinary catecholamine metabolite pattern was also consistently observed. The atypical presentation of this patient shows that the clinical and metabolic phenotype of TH deficiency is more variable than formerly thought, and that the condition should no longer be considered as a treatable disorder per se.

Eniluracil treatment completely inactivates dihydropyrimidine dehydrogenase in colorectal tumors

PURPOSE

To determine the effect of eniluracil on colorectal tumor dihydropyrimidine dehydrogenase (DPD) activity.

PATIENTS AND METHODS

Patients who were to undergo primary colorectal tumor resection received oral eniluracil 10 mg/m(2) twice daily for 3 days before surgery. Mononuclear cells were obtained before the start of eniluracil and on the morning of surgery, to measure DPD activity, protein, and mRNA. Plasma uracil was also measured at these two time points to assess the effect of eniluracil on pyrimidine accumulation. DPD activity, protein, and mRNA were also assessed in colorectal tumors and adjacent normal mucosa of patients who received eniluracil and untreated control patients.

RESULTS

DPD activity in tumors from 10 untreated patients ranged from 30 to 92 pmol/min/mg of protein. In contrast, there was no detectable tumor DPD activity in 10 patients who received eniluracil. A similar pattern was observed in mononuclear cells, where median pretherapy activity was 366.5 pmol/min/mg of protein (range, 265 to 494 pmol/min/mg of protein) and was undetectable immediately before surgery. Plasma uracil changed from a median less than 0.2 micromol/L before therapy to 27.76 micromol/L before surgery. No difference in DPD protein or mRNA was observed between pretherapy and presurgery mononuclear cell samples or between treated and untreated tumor samples.

CONCLUSION

This study provides definitive evidence that eniluracil completely inactivates DPD activity in human solid tumors. The increased plasma uracil and decreased DPD activity are consistent with systemic inactivation of the enzyme. The mechanism of inactivation is at the catalytic level, because no changes in DPD protein or mRNA were observed. Treatment with eniluracil will eliminate DPD activity as a source of pharmacokinetic fluorouracil variability or resistance in human colorectal cancer.

Genotype and phenotype in patients with dihydropyrimidine dehydrogenase deficiency

Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disease characterised by thymine-uraciluria in homozygous deficient patients and has been associated with a variable clinical phenotype. In order to understand the genetic and phenotypic basis for DPD deficiency, we have reviewed 17 families presenting 22 patients with complete deficiency of DPD. In this group of patients, 7 different mutations have been identified, including 2 deletions [295-298delTCAT, 1897delC], 1 splice-site mutation [IVS14+1G>A)] and 4 missense mutations (85T>C, 703C>T, 2658G>A, 2983G>T). Analysis of the prevalence of the various mutations among DPD patients has shown that the G-->A point mutation in the invariant splice donor site is by far the most common (52%), whereas the other six mutations are less frequently observed. A large phenotypic variability has been observed, with convulsive disorders, motor retardation and mental retardation being the most abundant manifestations. A clear correlation between the genotype and phenotype has not been established. An altered beta-alanine, uracil and thymine homeostasis might underlie the various clinical abnormalities encountered in patients with DPD deficiency.

Iatrogenic isolated isoleucine deficiency as the cause of an acrodermatitis enteropathica-like syndrome

We present two patients with a suspected inborn error of metabolism. A female newborn presented with dysmorphic features and convulsions. Metabolic screening suggested a defect in isoleucine degradation. Within 2 weeks after the introduction of an isoleucine-restricted diet, she developed a severe acrodermatitis enteropathica-like syndrome. The plasma level of isoleucine was low with a normal leucine/isoleucine ratio. The second patient, a female infant deficient in leucine as a result of a leucine-restricted diet, did not develop a dermatosis. Isoleucine is essential for normal growth and differentiation of keratinocytes and enterocytes. Deficiency of isoleucine, and not leucine or an imbalance in the leucine/isoleucine ratio, may result in an acrodermatitis enteropathica-like syndrome.

Monoamine oxidase A deficiency: biogenic amine metabolites in random urine samples

We have recently described an association between abnormal behaviour and monoamine oxidase A (MAO-A) deficiency in several males from a single large Dutch kindred. A characteristically abnormal excretion pattern of biogenic amine metabolites was present in 24-hour urine of affected males. Because of this strikingly abnormal metabolite pattern observed in 24 hour urine samples of MAO-A deficient males we hypothesized that it should be possible to diagnose this condition by examining random urine samples. We therefore studied multiple urine samples obtained over a two-week study period from two males with selective MAO-A deficiency. The results demonstrate that the characteristic abnormalities in the excretion of biogenic amines and their metabolites were faithfully present in every one of 12 independent samples obtained from the MAO-A deficient males over the two-week study period. We conclude that MAO-A deficiency can be reliably diagnosed by measuring the ratio of normetanephrine (NMN) to VMA (or that of NMN to MHPG) in random urine samples.

Inborn errors of pyrimidine degradation: clinical, biochemical and molecular aspects

The pyrimidines, uracil and thymine, are degraded in four steps. The first three steps of pyrimidine catabolism, controlled by enzyme shared by both pathways, result in the production of the neurotransmitter amino acid beta-alanine from uracil and the nonfunctional (R)-(-)-beta-aminoisobutyrate from thymine. The fourth step is controlled by several aminotransferases, which have different affinities for beta-alanine, beta-aminoisobutyrate and GABA. Defects concerning the first three steps all lead to a reduced production of beta-alanine; defects of the transaminases involving the metabolism of beta-alanine and GABA lead to accumulation of these neurotransmitter substances. In addition, other metabolites will accumulate or be reduced depending on the specific enzyme defect. Analysis of the abnormal concentrations of these metabolites in the body fluids is essential for the detection of patients with pyrimidine degradation defects. Clinically these disorders are often overlooked because symptomatology is highly aspecific. The growth in our knowledge concerning inborn errors of pyrimidine degradation has emphasized the importance of the clinical awareness of these defects as a possible cause of neurological disease and a contraindication for treatment of cancer patients with certain pyrimidine analogues. The various defects are discussed and attention is paid to clinical genetic and diagnostic aspects.

Specific genetic deficiencies of the A and B isoenzymes of monoamine oxidase are characterized by distinct neurochemical and clinical phenotypes

Monoamine oxidase (MAO) exists as two isoenzymes and plays a central role in the metabolism of monoamine neurotransmitters. In this study we compared the neurochemical phenotypes of previously described subjects with genetically determined selective lack of MAO-A or a lack of both MAO-A and MAO-B with those of two subjects with a previously described X chromosome microdeletion in whom we now demonstrate selective MAO-B deficiency. Mapping of the distal deletion breakpoint demonstrates its location in intron 5 of the MAO-B gene, with the deletion extending proximally into the Norrie disease gene. In contrast to the borderline mental retardation and abnormal behavioral phenotype in subjects with selective MAO-A deficiency and the severe mental retardation in patients with combined MAO-A/MAO-B deficiency and Norrie disease, the MAO-B-deficient subjects exhibit neither abnormal behavior nor mental retardation. Distinct neurochemical profiles characterize the three groups of MAO-deficient patients. In MAO-A-deficient subjects, there is a marked decrease in deaminated catecholamine metabolites and a concomitant marked elevation of O-methylated amine metabolites. These neurochemical changes are only slightly exaggerated in patients with combined lack of MAO-A and MAO-B. In contrast, the only biochemical abnormalities detected in subjects with the MAO-B gene deletion are a complete absence of platelet MAO-B activity and an increased urinary excretion of phenylethylamine. The differences in neurochemical profiles indicate that, under normal conditions, MAO-A is considerably more important than MAO-B in the metabolism of biogenic amines, a factor likely to contribute to the different clinical phenotypes.

Vitamin-responsive complex I deficiency in a myopathic patient with increased activity of the terminal respiratory chain and lactic acidosis

An 11-year-old girl with exercise intolerance, fatiguability from early childhood, had high blood lactate levels. Histochemistry showed increased activity of succinate dehydrogenase at the periphery of the muscle fibres, whereas aggregates of mitochondria were seen by electron microscopy. Biochemical investigation of isolated mitochondria and homogenate from muscle showed evidence of a severe complex I deficiency. In contrast, succinate dehydrogenase, complex II+III and complex IV were increased in activity. Therapy with biotin, riboflavin, nicotinamide, carnitine and amino acids resulted in an improvement of her endurance. 31P NMR spectroscopy of her forearm muscle showed a decreased ratio of phosphocreatine (PCr) over ATP. After exercise the PCr recovery rate was 26% of the average rate in 20 healthy untrained controls. When the therapy was suspended the PCr/ATP ratio at rest decreased from 2.60 to 2.34, and the PCr recovery rate after exercise decreased to 21% of the average control rate. The therapy was reinstituted but only riboflavin and carnitine were given. The PCr/ATP ratio increased to 2.60 and the PCr recovery rate increased to 32% of the control rate. Improvement of the energy metabolism in patients with defects in the oxidative phosphorylation may add to the quality of life; 31P NMR spectroscopy can measure these improvements.

Molybdenum-cofactor deficiency: an easily missed cause of neonatal convulsions

Intractable seizures in the neonatal period may be caused by molybdenum-cofactor deficiency, an inborn error which combines the deficiencies of sulphite oxidase and xanthine dehydrogenase. The neurological symptoms of molybdenum cofactor and isolated sulphite oxidase deficiencies are identical. Two new cases are reported, and the literature on neonatal convulsions due to molybdenum-cofactor and sulphite deficiencies is reviewed. Because of the high incidence of neonatal convulsions a search for this deficiency is advocated in each case of unexplained refractory neonatal convulsions. Diagnosis may be missed or delayed on standard metabolic screening for several reasons discussed. By simply using a sulphite strip test in a fresh urine sample an indication for the defect can be obtained. Antenatal diagnosis can be performed by assay of sulphite oxidase activity in a chorionic villus sample.

X-linked borderline mental retardation with prominent behavioral disturbance: phenotype, genetic localization, and evidence for disturbed monoamine metabolism

We have identified a large Dutch kindred with a new form of X-linked nondysmorphic mild mental retardation. All affected males in this family show very characteristic abnormal behavior, in particular aggressive and sometimes violent behavior. Other types of impulsive behavior include arson, attempted rape, and exhibitionism. Attempted suicide has been reported in a single case. The locus for this disorder could be assigned to the Xp11-21 interval between DXS7 and DXS77 by linkage analysis using markers spanning the X chromosome. A maximal multipoint lod score of 3.69 was obtained at the monoamine oxidase type A (MAOA) locus in Xp11.23-11.4. Results of 24-h urine analysis in three affected males indicated a marked disturbance of monoamine metabolism. These data are compatible with a primary defect in the structural gene for MAOA and/or monoamine oxidase type B (MAOB). Normal platelet MAOB activity suggests that the unusual behavior pattern in this family may be caused by isolated MAOA deficiency.

Deficiency of the adenine nucleotide translocator in muscle of a patient with myopathy and lactic acidosis: a new mitochondrial defect

In a patient with a mitochondrial myopathy, presenting with lactic acidosis, 31P-nuclear magnetic resonance spectroscopy in resting muscle showed half the creatine phosphate level of controls. The creatine phosphate resynthesis rate after aerobic exercise was only 18% of that in controls. However, the activities of complexes I to V catalyzing oxidative phosphorylation and the pyruvate and the 2-oxoglutarate dehydrogenase complexes showed a 2- to 20-fold increase. In line with this, the uncoupled mitochondrial respiration rate was significantly higher than in controls. In contrast, the respiration of the mitochondria from the patient was less stimulated by ADP than that of control mitochondria. This finding could point to a defect in complex V, the enzyme directly involved in ATP synthesis. The activity of complex V, measured as the mitochondrial ATPase activity, and its concentration, as judged from Western blots using antisera against the F1 part of complex V, were, however, also greatly increased in the patient. Alternatively, the transport system, importing ADP into and exporting ATP out of the mitochondrial matrix, the ADP/ATP or adenine nucleotide translocator, could be affected. Immunostaining of Western blots revealed a 4-fold decrease in the concentration of the adenine nucleotide translocator in the patient. Because oxidative phosphorylation was not disturbed in fibroblasts and lymphocytes, we conclude that this patient suffers from a muscle-specific deficiency of his mitochondrial adenine nucleotide translocator, a defect unknown so far.

Application of simple chromatographic methods for the diagnosis of defects in pyrimidine degradation

Recent findings suggest that inborn errors of pyrimidine catabolism are less rare than generally assumed. We propose a complete set of diagnostic methods for these disorders, suitable for the clinical chemistry laboratory, and present relevant reference data. Applications of thin-layer chromatography, high-performance liquid chromatography, and conventional cation-exchange amino acid analysis lead to detection of various defects in pyrimidine degradation, including the recently described deficiencies of dihydropyrimidine dehydrogenase and dihydropyrimidinase. We also illustrate the potential of the methods to analyze for the catabolites expected to be increased in the urine of patients with ureidopropionase deficiency. Possible pitfalls in the diagnosis and ways to prevent misdiagnosis are demonstrated. The methods offer possibilities for clinical chemistry laboratories to extend their diagnostic capacity to the new area of pyrimidine degradation defects.

Application of simple chromatographic methods for the diagnosis of defects in pyrimidine degradation

Recent findings suggest that inborn errors of pyrimidine catabolism are less rare than generally assumed. We propose a complete set of diagnostic methods for these disorders, suitable for the clinical chemistry laboratory, and present relevant reference data. Applications of thin-layer chromatography, high-performance liquid chromatography, and conventional cation-exchange amino acid analysis lead to detection of various defects in pyrimidine degradation, including the recently described deficiencies of dihydropyrimidine dehydrogenase and dihydropyrimidinase. We also illustrate the potential of the methods to analyze for the catabolites expected to be increased in the urine of patients with ureidopropionase deficiency. Possible pitfalls in the diagnosis and ways to prevent misdiagnosis are demonstrated. The methods offer possibilities for clinical chemistry laboratories to extend their diagnostic capacity to the new area of pyrimidine degradation defects.

Neonatal cardiomyopathy and lactic acidosis responsive to thiamine

A congestive cardiomyopathy was diagnosed in a girl at the age of 4 weeks. In the weeks following she developed general muscle hypotonia and plasma lactate increased to 8.5 mmol/L. Biochemical investigations of a muscle biopsy at the age of 3 months showed a deficiency in the oxidation of all substrates tested: pyruvate plus malate, 2-ketoglutarate and palmitate plus malate. After freezing and thawing of the homogenate and the addition of essential cofactors, the oxidation of the ketoacids normalized. The oxidation defect in the untreated homogenate can be explained by a deficiency in one of the cofactors (such as thiamine pyrophosphate, NAD+ or CoASH), or by a defect in the oxidative phosphorylation. Treatment with thiamine and carnitine resulted in a decrease in blood lactate to normal levels and a dramatic clinical improvement. Suspension of thiamine caused deterioration of her clinical condition and lactic acidaemia. The thiamine therapy was then continued. The girl is now 6 years old and in perfect health.

Simultaneous determination of acidic 3,4-dihydroxyphenylalanine metabolites and 5-hydroxyindole-3-acetic acid in urine by high-performance liquid chromatography

We describe a simple and rapid quantitative method for the simultaneous determination of 3,4-dihydroxyphenylalanine acid metabolites and 5-hydroxyindole-3-acetic acid. After solvent extraction from acidified urine, the acids are analyzed by reversed-phase high-performance liquid chromatography. For detection and quantification, we used a fluorescence detector in combination with an amperometric detector to obtain a high degree of specificity. Sample preparation and chromatographic analysis can be completed within an hour. Results by the method correlate well with those by a previously used gas-chromatographic method, but the new method is faster and avoids the need for derivatization.

Simultaneous determination of acidic 3,4-dihydroxyphenylalanine metabolites and 5-hydroxyindole-3-acetic acid in urine by high-performance liquid chromatography

We describe a simple and rapid quantitative method for the simultaneous determination of 3,4-dihydroxyphenylalanine acid metabolites and 5-hydroxyindole-3-acetic acid. After solvent extraction from acidified urine, the acids are analyzed by reversed-phase high-performance liquid chromatography. For detection and quantification, we used a fluorescence detector in combination with an amperometric detector to obtain a high degree of specificity. Sample preparation and chromatographic analysis can be completed within an hour. Results by the method correlate well with those by a previously used gas-chromatographic method, but the new method is faster and avoids the need for derivatization.

Diagnosis and treatment of malignant pheochromocytoma with 131I-meta-iodobenzylguanidine: a case report

The case of a 67-year-old male patient with metastatic malignant pheochromocytoma is described to illustrate the significant improvement of the diagnosis and treatment of pheochromocytoma since the recent introduction of 131I-meta-iodobenzylguanidine (131I-MIBG). Because of the generally observed tumor heterogeneity as to 131I-MIBG uptake and radiosensitivity in advanced disease, treatment results may be improved further, if 131I-MIBG therapy is initiated when tumor load is still small.

The role of I-131-MIBG in the diagnosis and therapy of carcinoids

The successful use of 131I-MIBG for the diagnosis and treatment of pheochromocytoma and neuroblastoma has led to its application in patients with carcinoid, another neural crest tumor. The present report describes the scintigraphic findings, in correlation with clinical and biochemical parameters, in 20 patients with histologically proven carcinoids. 131I-MIBG total body scintigraphy was positive in 12 and equivocal in 1 of 19 patients with metastases. The necessity of delayed imaging and the possible advantage of single photon emission tomography for the detection of this tumor are emphasized. The results of 131I-MIBG treatment in five patients with progressive carcinoid metastases are discussed. It is concluded that 131I-MIBG has a role in the work up of patients with proven carcinoid and can be used for palliative treatment of this tumor.

beta-Aminoisobutyric acid as a marker of thymine catabolism in malignancy

Urine from untreated patients with various tumours and controls has been examined for the excretion of beta-aminoisobutyric acid and uric acid. The patients were classified into four groups: I, beta-aminoisobutyric acid and uric acid both normal; II, beta-aminoisobutyric acid normal, uric acid elevated; III, beta-aminoisobutyric acid elevated, uric acid normal; IV, beta-aminoisobutyric acid and uric acid both elevated. Uric acid was used as an indicator for tissue-breakdown. Pseudouridine being a specific parameter for t-RNA degradation was estimated for comparison. Increased urinary concentrations of beta-aminoisobutyric acid were frequently found in tumour patients, especially in patients with leukaemia and non-Hodgkin lymphoma. Tissue breakdown being the cause of the beta-aminoisobutyric aciduria could only be considered in part of the patients. Moreover, strongly elevated ratios of beta-aminoisobutyric acid to uric acid were found. Urinary patterns of pyrimidines and purines were determined in order to exclude other abnormalities. The results are discussed in relation to thymine metabolism and renal function.

Biochemical monitoring of children with neuroblastoma

In this article, a short review is given of the biochemical aspects of diagnosis, estimation of prognosis and follow-up of neuroblastoma in children. The importance of determination of patterns of DOPA-metabolites, rather than single metabolite assay, is stressed and illustrated by patient cases. Also the relevance of urinary cystathionine and beta-amino-isobutyric acid is indicated.