Cerebrospinal Fluid Pterins, Pterin-Dependent Neurotransmitters, and Mortality in Pediatric Cerebral Malaria

BACKGROUND

Cerebral malaria (CM) pathogenesis remains incompletely understood. Having shown low systemic levels of tetrahydrobiopterin (BH4), an enzymatic cofactor for neurotransmitter synthesis, we hypothesized that BH4 and BH4-dependent neurotransmitters would likewise be low in cerebrospinal fluid (CSF) in CM.

METHODS

We prospectively enrolled Tanzanian children with CM and children with nonmalaria central nervous system conditions (NMCs). We measured CSF levels of BH4, neopterin, and BH4-dependent neurotransmitter metabolites, 3-O-methyldopa, homovanillic acid, and 5-hydroxyindoleacetate, and we derived age-adjusted z-scores using published reference ranges.

RESULTS

Cerebrospinal fluid BH4 was elevated in CM (n = 49) compared with NMC (n = 51) (z-score 0.75 vs -0.08; P < .001). Neopterin was increased in CM (z-score 4.05 vs 0.09; P < .001), and a cutoff at the upper limit of normal (60 nmol/L) was 100% sensitive for CM. Neurotransmitter metabolite levels were overall preserved. A higher CSF BH4/BH2 ratio was associated with increased odds of survival (odds ratio, 2.94; 95% confidence interval, 1.03-8.33; P = .043).

CONCLUSION

Despite low systemic BH4, CSF BH4 was elevated and associated with increased odds of survival in CM. Coma in malaria is not explained by deficiency of BH4-dependent neurotransmitters. Elevated CSF neopterin was 100% sensitive for CM diagnosis and warrants further assessment of its clinical utility for ruling out CM in malaria-endemic areas.

Cerebrospinal fluid monoamines, pterins, and folate in patients with mitochondrial diseases: systematic review and hospital experience

Mitochondrial diseases are a group of genetic disorders leading to the dysfunction of mitochondrial energy metabolism pathways. We aimed to assess the clinical phenotype and the biochemical cerebrospinal fluid (CSF) biogenic amine profiles of patients with different diagnoses of genetic mitochondrial diseases. We recruited 29 patients with genetically confirmed mitochondrial diseases harboring mutations in either nuclear or mitochondrial DNA (mtDNA) genes. Signs and symptoms of impaired neurotransmission and neuroradiological data were recorded. CSF monoamines, pterins, and 5-methyltetrahydrofolate (5MTHF) concentrations were analyzed using high-performance liquid chromatography with electrochemical and fluorescence detection procedures. The mtDNA mutations were studied by Sanger sequencing, Southern blot, and real-time PCR, and nuclear DNA was assessed either by Sanger or next-generation sequencing. Five out of 29 cases showed predominant dopaminergic signs not attributable to basal ganglia involvement, harboring mutations in different nuclear genes. A chi-square test showed a statistically significant association between high homovanillic acid (HVA) values and low CSF 5-MTHF values (chi-square = 10.916; p = 0.001). Seven out of the eight patients with high CSF HVA values showed cerebral folate deficiency. Five of them harbored mtDNA deletions associated with Kearns-Sayre syndrome (KSS), one had a mitochondrial point mutation at the mtDNA ATPase6 gene, and one had a POLG mutation. In conclusion, dopamine deficiency clinical signs were present in some patients with mitochondrial diseases with different genetic backgrounds. High CSF HVA values, together with a severe cerebral folate deficiency, were observed in KSS patients and in other mtDNA mutation syndromes.

Sepiapterin reductase deficiency: Report of 5 new cases

BACKGROUND

Sepiapterin reductase deficiency is a rare, under-recognized, autosomal recessively inherited disorder of neurotransmitter metabolism.

CASE REPORT

Five new patients from 3 unrelated Saudi consanguineous families are reported. Symptoms began at 6 months, with delay to diagnosis averaging 8 years. All 5 patients presented with severe symptoms including axial hypotonia, dystonia, and cognitive impairment, associated with hyper-reflexia (4 patients), spasticity (4 patients), bulbar dysfunction (4 patients), and oculogyric crisis (2 patients) with diurnal fluctuation and sleep benefit. Cerebrospinal fluid neurotransmitters analysis showed a typical pattern with increased sepiapterin and increased 7,8-dihydrobiopterin. Analysis of the SPR gene identified 3 novel mutations: c.1A > G, c.370T > C, and c.527C > T. Patient one, with early diagnosis, is currently developing within the normal range. The 4 other patients showed significant improvement in their motor function, but only mild improvement in their cognitive dysfunction.

CONCLUSION

Our cases illustrate the difficulties in the diagnosis of sepiapterin reductase deficiency in infancy, and the importance of early recognition and management.

Two Greek siblings with sepiapterin reductase deficiency

BACKGROUND

Sepiapterin reductase (SR) deficiency is a rare inherited disorder of neurotransmitter metabolism; less than 25 cases have been described in the literature so far.

METHODS

We describe the clinical history and extensive cerebrospinal fluid (CSF) and urine examination of two Greek siblings with the diagnosis of SR deficiency. The diagnosis was confirmed by enzyme activity measurement in cultured fibroblasts and by mutation analysis.

RESULTS

Both patients suffered from a progressive and complex L-dopa responsive movement disorder. Very low concentrations of the neurotransmitter metabolites homovanillic acid (HVA), 5-hydroxyindolacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) were observed in CSF. CSF neopterin and biopterin concentrations were abnormal in one case only, whereas in both cases sepiapterin concentrations were abnormally high and 5-hydroxytryptophan was undetectable. Urine concentrations of HVA, 5-HIAA and vanillyl mandelic acid (VMA) were decreased in both cases. Both patients had no detectable SR enzyme activity in primary dermal fibroblasts, and upon analysis of genomic DNA revealed the same homozygous point mutation introducing a premature stop codon into the reading frame of the SPR gene (mutant allele K251X).

CONCLUSIONS

Our cases illustrate that, apart from HVA and 5-HIAA analysis, the specific quantification of sepiapterin in CSF, rather than neopterin and biopterin alone, is crucial to the final diagnosis of SR deficiency. In addition, urinary concentrations of neurotransmitter metabolites may be abnormal in SR deficiency and may provide an initial indication of SR deficiency before CSF analysis is performed. The known, impressive beneficial response of SR deficient patients to treatment with L-dopa, is illustrated again in our cases.

Secondary abnormalities of neurotransmitters in infants with neurological disorders

Neurotransmitters are essential in young children for differentiation and neuronal growth of the developing nervous system. We aimed to identify possible factors related to secondary neurotransmitter abnormalities in pediatric patients with neurological disorders. We analyzed cerebrospinal fluid (CSF) and biogenic amine metabolites in 56 infants (33 males, 23 females; mean age 5.8mo [SD 4.1mo] range 1d-1y) with neurological disorders whose aetiology was initially unknown. Patients were classified into three clinical phenotypes: epileptic encephalopathy, severe motor impairment, and non-specific manifestations. All patients showed normal results for screening of inborn errors of metabolism. We report clinical, neuroimaging, and follow-up data. Among the patients studied, 10 had low homovanillic acid (HVA) levels and in four patients, 5-hydroxyindoleacetic acid (5-HIAA) was also reduced. Patients with neonatal onset had significantly lower levels of HVA than a comparison group. HVA deficiency was also associated with severe motor impairment and the final diagnosis related to neurodegenerative disorders. 5-HIAA values tended to be decreased in patients with brain cortical atrophy. The possibility of treating patients with L-Dopa and 5-hydroxytryptophan, in order to improve their neurological function and maturation, may be considered.

Utilidad del análisis del líquido cefalorraquídeo para el estudio de las deficiencias del metabolismo de neurotransmisores y pterinas y del transporte de glucosa y folato a través de la barrera hematoencefálica

BACKGROUND AND OBJECTIVE

In the last few years, it has been described inborn errors of neurotransmitter and pterin metabolism and defects in folate and glucose transport across blood brain barrier. All these defects are classified as rare diseases and needs cerebrospinal fluid (CSF) sample analysis for diagnosis. Our aim was to evaluate the results of the application of a CSF analysis protocol in a pediatric population from Spain and Portugal presenting with neurological disorders of unknown origin.

PATIENTS AND METHOD

We studied CSF samples from and 283 patients with neurological disorders of unknown origin and 127 controls. Neurotransmitters were analysed by HPLC with electrochemical detection, and pterins and 5-methyltetrahydrofolate were determined by HPLC with fluorescence detection.

RESULTS

We diagnosed 3 patients with tyrosine hidroxylase deficiency, 2 with dopa responsive dystonia, 14 with GTP-ciclohydrolase deficiency, 2 with glucose transport deficiency and 43 with cerebral folate deficiency.

CONCLUSIONS

This study allowed us to diagnose new patients, and more importantly, the establishment in all of them of a pharmacological or nutritional treatment. The most frequent defect found was CSF 5-methyltetrahydrofolate deficiency, which was present in different groups of patients.

Detection of 28 neurotransmitters and related compounds in biological fluids by liquid chromatography/tandem mass spectrometry

This work presents two liquid chromatography/tandem mass spectrometry (LC/MS/MS) acquisition modes: multiple reaction monitoring (MRM) and neutral loss scan (NL), for the analysis of 28 compounds in a mixture. This mixture includes 21 compounds related to the metabolism of three amino acids: tyrosine, tryptophan and glutamic acid, two pterins and five deuterated compounds used as internal standards. The identification of compounds is achieved using the retention times (RT) and the characteristic fragmentations of ionized compounds. The acquisition modes used for the detection of characteristic ions turned out to be complementary: the identification of expected compounds only is feasible by MRM while expected and unexpected compounds are detected by NL. In the first part of this work, the fragmentations characterizing each molecule of interest are described. These fragmentations are used in the second part for the detection by MRM and NL of selected compounds in mixture with and without biological fluids. Any preliminary extraction precedes the analysis of compounds in biological fluids.

HPLC with electrochemical and fluorescence detection procedures for the diagnosis of inborn errors of biogenic amines and pterins

The analysis of biogenic amines (BA) and pterins in cerebrospinal fluid (CSF) is essential for the early diagnosis of neurotransmission defects in the paediatric age. Our aim was to standardize previously reported HPLC procedures for the analysis of BA and pterins in CSF and to establish reference values for a paediatric population. Samples from 127 subjects (age range 11 days to 16 years; average 3.8) were analyzed by HPLC with electrochemical and fluorescence detection. Both BA (homovanilic and 5-hydroxyindoleacetic acid) and pterins (neopterin and biopterin) concentrations in CSF showed a negative correlation with age. This finding led us to stratify reference values into six groups according to age. In conclusion, analysis of BA and pterins in CSF by HPLC procedures is a useful set of tools for the diagnosis of inborn errors of metabolism of these compounds. The establishment of reference intervals may be difficult, since there is a strong correlation between BA concentrations and the age of controls and, as a result, a large number of CSF samples from control populations would be necessary for this purpose.

Cerebrospinal fluid pterins and folates in Aicardi-Goutières syndrome: a new phenotype

OBJECTIVE

To describe three unrelated children with a distinctive variant of Aicardi-Goutières syndrome (AGS) characterized by microcephaly, severe mental and motor retardation, dyskinesia or spasticity, and occasional seizures.

RESULTS

Neuroimaging showed bilateral calcification of basal ganglia and white matter. CSF glucose, protein, cell count, and interferon alpha were normal. Abnormal CSF findings included extremely high neopterin (293 to 814 nmol/L; normal 12 to 30 nmol/L) and biopterin (226 to 416 nmol/L; normal 15 to 40 nmol/L) combined with lowered 5-methyltetrahydrofolate (23 to 48 nmol/L; normal 64 to 182 nmol/L) concentrations in two patients. The absence of pleocytosis and normal CSF interferon alpha was a characteristic finding compared to the classic AGS syndrome. Genetic and enzymatic tests excluded disorders of tetrahydrobiopterin metabolism, including mutation analysis of GTP cyclohydrolase feed-back regulatory protein. CSF investigations in three patients with classic AGS also showed increased pterins and partially lowered folate levels.

CONCLUSIONS

Intrathecal overproduction of pterins is the first biochemical abnormality identified in patients with AGS variants. Long-term substitution with folinic acid (2-4 mg/kg/day) resulted in substantial clinical recovery with normalization of CSF folates and pterins in one patient and clinical improvement in another. The underlying defect remains unknown.

R208X mutation in CLN2 gene associated with reduced cerebrospinal fluid pterins in a girl with classic late infantile neuronal ceroid lipofuscinosis

Clinical picture of neuronal ceroid lipofuscinosis with late infantile onset (LINCL) is characterized by myoclonic seizures and psychomotor regression. We present a case of classic LINCL and reduced cerebrospinal fluid (CSF) pterins in a girl of normal psychomotor development and born to non-consanguineous parents. She first presented with febrile seizures at the age of four. At that time, brain computed tomography finding was normal, but electroencephalogram showed hypsarrhythmia. At the age of five, tremor, generalized ataxia, and motor and mental regression appeared. Brain magnetic resonance imaging showed cerebellar atrophy. Electron microscopy examination showed storage of intracytoplasmic curvilinear inclusions in neurons, fibroblasts, and secretory cells of the skin and rectal mucosa. Tripeptidyl peptidase I (TPP-I) activity in leukocytes was very low (5.4 nmol/h/mg protein; range in homozygote cases of LINCL, 0.4-26.0). Molecular genetic studies showed a homozygous mutation, R208X, in exon 6 of CLN2 gene. CSF analysis revealed very low neopterin (7.3 nmol/L; normal range, 9-30) and biopterin (4.1 nmol/L; normal range, 10-30), reduced homovanillic acid (266 nmol/L; normal range, 211-871), and low homovanillic acid/5-hydroxyindoleacetic acid ratio (1.21; normal ratio, 1.5-3.5). Treatment with L-Dopa/Carbidopa (4 mg/kg) and antiepileptics was introduced, but without significant effect. It seems that low CSF pterins and impaired dopamine turnover are secondary manifestations of classical LINCL caused by homozygous inheritance of the R208X mutation in CLN2 gene.

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.

Identification of mutations causing 6-pyruvoyl-tetrahydropterin synthase deficiency in four Italian families

6-Pyruvoyl-tetrahydrobiopterin synthase (PTPS) is involved in tetrahydrobiopterin (BH4) biosynthesis, the cofactor for various enzymes including the hepatic phenylalanine hydroxylase. Inherited PTPS deficiency leads to BH4 depletion, causes hyperphenylalaninemia, and requires cofactor replacement therapy for treatment. We previously isolated the human PTPS cDNA and recently characterized its corresponding gene, PTS. Here we developed PCR-based mutation analysis with newly designed primers to detect genomic alterations and describe five mutations, four of which are novel, in the PTS gene of four Italian families with affected individuals. The mutant alleles found included three missense mutations (T67M, K129E, D136V), a previously described triplet deletion (delta V57), and a single c-3-->g transversion in the 3'-acceptor splice site of intron 1, leading to cryptic splice site usage that resulted in a 12 bp deletion (mutant allele delta (K29-S32)). Except for K129E, all mutant alleles were inactive and/or unstable proteins, as shown by recombinant expression and Western blot analysis of patients' fibroblasts. The PTPS-deficient patient with the homozygous K129E allele had transient hyperphenylalaninemia, did not depend on BH4 replacement therapy, and showed normal PTPS immunoreactivity, but no enzyme activity in primary fibroblasts and red blood cells. In contrast to its inactivity in these cells, the K129E mutant was 2-3 fold more active than wild-type PTPS when transfected into COS-1 or the human hepatoma cell line Hep G2. K129E appears thus as a mutant PTPS whose activity depends on the cell type.

Cerebrospinal fluid concentrations of pterins and metabolites of serotonin and dopamine in a pediatric reference population

Accurate diagnosis and management of inborn errors of monoamine neurotransmitter and tetrahydrobiopterin metabolism depend on reliable reference ranges of key metabolites. Cerebrospinal fluid (CSF) was collected in a standardized way from 73 children and young adults with neurologic disease, with strict exclusions. In each specimen, concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (HIAA), total neopterin, 7,8-dihydrobiopterin, and tetrahydrobiopterin (BH4) were measured using HPLC. There was a continuous decrement in CSF HVA, HIAA, and BH4 during the first few years of life; this was independent of height (or length). Age-related reference ranges for each metabolite are given. Extensive correlations between HVA, HIAA, 7,8-dihydrobiopterin, and BH4 were further analyzed by multiple regression. Age and CSF BH4 were significant explanatory variables for CSF HIAA, but CSF HVA had only HIAA as a significant explanatory variable.

Atypical (mild) forms of dihydropteridine reductase deficiency: neurochemical evaluation and mutation detection

We investigated two patients with an atypical (mild) form of dihydropteridine reductase (DHPR) deficiency. Both responded to the loading test with tetrahydrobiopterin; their plasma phenylalanine levels were lowered from 278 mumol/L to 85 and 48 mumol/L and from 460 mumol/L to 97 and 36 mumol/L after 4 and 8 h, respectively. In one of the patients, a combined loading test with phenylalanine followed by tetrahydrobiopterin was also carried out and showed a profile typical for DHPR deficiency. The phenylalanine hydroxylation rate was calculated to be 43 and 87%, 4 and 8 h after cofactor administration, respectively. Diagnosis was confirmed by the absence of DHPR activity in the patient's erythrocytes. In cultured fibroblasts, residual activity of 4 and 10%, respectively, was found. Excretion of urinary pterins was essentially normal, and the biopterin to neopterin ratio in cerebrospinal fluid was increased. Although in both patients cerebrospinal fluid homovanillic acid was found to be normal, and 5-hydroxyindoleacetic acid was substantially reduced, there was no sign of neurologic alterations until the age of 2 y. However, one of the patients recently developed deceleration of head growth, whereas psychomotor development continued to be normal for age. Using the chemical cleavage method on the amplified cDNA, mismatches of T to G at nucleotide 659 and of G to A at nucleotide 475, respectively, were identified. These results also demonstrate that screening for tetrahydrobiopterin deficiency by urinary pterin analysis alone can miss some newborns with mild DHPR deficiency and that all children with tetrahydrobiopterin defects need full neurochemical evaluation together with analysis of the enzyme activity.

Estimation of tetrahydrobiopterin and other pterins in cerebrospinal fluid using reversed-phase high-performance liquid chromatography with electrochemical and fluorescence detection

We describe an isocratic, reversed-phase high-performance liquid chromatographic method for the simultaneous measurement of fully oxidised, dihydro- and tetrahydropterins in cerebrospinal fluid. Tetrahydrobiopterin is detected electrochemically using an ESA Coulochem detector in the redox mode. Dihydropterins are detected by fluorescence following post-column electrochemical oxidation, and fully oxidised pterins by their natural fluorescence. Apart from addition of antioxidants, no sample preparation is required. Comparison is made with methods requiring chemical oxidation for detection of tetrahydrobiopterin. Some results on children with neurological disease are presented.

High-performance liquid chromatography with column switching for the analysis of biogenic amine metabolites and pterins

An automatic high-performance liquid chromatographic system with facilities for column switching is described which involves minimal pre-treatment of biological samples, separates complex mixtures of compounds in a short period of time and uses fluorimetric or amperometric detection. The system has been applied to the analysis of oxidized pterins in urine and reduced pterins in cerebrospinal fluid and rat brain fractions (R- and S-enantiomers of tetrahydrobiopterin resolved). The system can also be used for the analysis of most of the dopamine and serotonin metabolites in cerebrospinal fluid and brain fractions from norepinephrine to serotonin.

Use of tetrahydropterins in the treatment of hyperphenylalaninemia due to defective synthesis of tetrahydrobiopterin: evidence that peripherally administered tetrahydropterins enter the brain

Substantial amounts of tetrahydrobiopterin and 6-methyltetrahydropterin can be detected in CSF when these pterins are given peripherally to patients with hyperphenylalaninemia due to defective biopterin synthesis. Results of this study suggest that administration of either of these pterins in proper doses may prove to be a treatment not only for the impaired peripheral phenylalanine metabolism, but also for the neurologic disorders that are characteristic of the variant forms of hyperphenylalaninemia due to defective tetrahydrobiopterin synthesis or metabolism.

CFS hydroxylase cofactor levels in some neurological diseases

The cerebrospinal fluid concentration of hydroxylase cofactor has been measured in patients with Parkinson's disease, the Shy-Drager and Steele-Richardson syndromes, adult onset focal dystonia, essential tremor, Huntington's disease and presenile dementia. The results were compared with age matched controls and low values were demonstrated for all disease groups studied except for focal dystonia.