Neuroblastoma stage 4S: Tumor regression rate and risk factors of progressive disease.

BACKGROUND: The clinical course of neuroblastoma stage 4S or MS is characterized by a high rate of spontaneous tumor regression and favorable outcome. However, the clinical course and rate of the regression are poorly understood. METHODS: A retrospective cohort study was performed, including all patients with stage 4S neuroblastoma without MYCN amplification, from two Dutch centers between 1972 and 2012. We investigated the clinical characteristics, the biochemical activity reflected in urinary catecholamine excretion, and radiological imaging to describe the kinetics of tumor regression, therapy response and outcome. RESULTS: The cohort of 31 patients reached a 10-year overall survival of 84% ± 7% (median follow-up 16 years; range, 3.3-39). During the regressive phase, liver size normalized in 91% of the patients and catecholamine excretion in 83%, both after a median of two months (liver size: range, 0-131; catecholamines: range, 0-158). The primary tumors completely regressed in 69% after 13 months (range, 6-73), and the liver architecture normalized in 52% after 15 months (range, 5-131). Antitumor treatment was given in 52% of the patients. Interestingly, regression rates were similar for treated and untreated patients. Four of seven patients < 4 weeks old died of rapid liver expansion and organ compression. Three patients progressed to stage 4, 3 to 13 months after diagnosis; all had persistently elevated catecholamines. CONCLUSION: Patients < 4 weeks old with neuroblastoma stage 4S are at risk of fatal outcome caused by progression of liver metastases. In other patients, tumor regression is characterized by a rapid biochemical normalization that precedes radiological regression.

Infantile hypophosphatasia without bone deformities presenting with severe pyridoxine-resistant seizures.

An infant carrying a heterozygous c.43_46delACTA and a heterozygous c.668 G>A mutation in the ALPL gene with hypophosphatasia in the absence of bone deformities presented with therapy-resistant seizures. Pyridoxal phosphate was extremely high in CSF and plasma. Pyridoxine treatment had only a transient effect and the severe encephalopathy was fatal. Repeated brain MRIs showed progressive cerebral damage. The precise metabolic cause of the seizures remains unknown and pyridoxine treatment apparently does not cure the epilepsy.

Clinical, biochemical and molecular analysis of 13 Japanese patients with ß-ureidopropionase deficiency demonstrates high prevalence of the c.977G > A (p.R326Q) mutation [corrected].

ß-ureidopropionase (ßUP) deficiency is an autosomal recessive disease characterized by N-carbamyl-ß-amino aciduria. To date, only 16 genetically confirmed patients with ßUP deficiency have been reported. Here, we report on the clinical, biochemical and molecular findings of 13 Japanese ßUP deficient patients. In this group of patients, three novel missense mutations (p.G31S, p.E271K, and p.I286T) and a recently described mutation (p.R326Q) were identified. The p.R326Q mutation was detected in all 13 patients with eight patients being homozygous for this mutation. Screening for the p.R326Q mutation in 110 Japanese individuals showed an allele frequency of 0.9 %. Transient expression of mutant ßUP enzymes in HEK293 cells showed that the p.E271K and p.R326Q mutations cause profound decreases in activity (≤ 1.3 %). Conversely, ßUP enzymes containing the p.G31S and p.I286T mutations possess residual activities of 50 and 70 %, respectively, suggesting we cannot exclude the presence of additional mutations in the non-coding region of the UPB1 gene. Analysis of a human ßUP homology model revealed that the effects of the mutations (p.G31S, p.E271K, and p.R326Q) on enzyme activity are most likely linked to improper oligomer assembly. Highly variable phenotypes ranging from neurological involvement (including convulsions and autism) to asymptomatic, were observed in diagnosed patients. High prevalence of p.R326Q in the normal Japanese population indicates that ßUP deficiency is not as rare as generally considered and screening for ßUP deficiency should be included in diagnosis of patients with unexplained neurological abnormalities.

ß-ureidopropionase deficiency: phenotype, genotype and protein structural consequences in 16 patients.

ß-ureidopropionase is the third enzyme of the pyrimidine degradation pathway and catalyzes the conversion of N-carbamyl-ß-alanine and N-carbamyl-ß-aminoisobutyric acid to ß-alanine and ß-aminoisobutyric acid, ammonia and CO(2). To date, only five genetically confirmed patients with a complete ß-ureidopropionase deficiency have been reported. Here, we report on the clinical, biochemical and molecular findings of 11 newly identified ß-ureidopropionase deficient patients as well as the analysis of the mutations in a three-dimensional framework. Patients presented mainly with neurological abnormalities (intellectual disabilities, seizures, abnormal tonus regulation, microcephaly, and malformations on neuro-imaging) and markedly elevated levels of N-carbamyl-ß-alanine and N-carbamyl-ß-aminoisobutyric acid in urine and plasma. Analysis of UPB1, encoding ß-ureidopropionase, showed 6 novel missense mutations and one novel splice-site mutation. Heterologous expression of the 6 mutant enzymes in Escherichia coli showed that all mutations yielded mutant ß-ureidopropionase proteins with significantly decreased activity. Analysis of a homology model of human ß-ureidopropionase generated using the crystal structure of the enzyme from Drosophila melanogaster indicated that the point mutations p.G235R, p.R236W and p.S264R lead to amino acid exchanges in the active site and therefore affect substrate binding and catalysis. The mutations L13S, R326Q and T359M resulted most likely in folding defects and oligomer assembly impairment. Two mutations were identified in several unrelated ß-ureidopropionase patients, indicating that ß-ureidopropionase deficiency may be more common than anticipated.

S-adenosylmethionine and S-adenosylhomocysteine in plasma and cerebrospinal fluid in Rett syndrome and the effect of folinic acid supplementation.

Rett syndrome is a neurodevelopmental disorder characterized by cognitive and locomotor regression and stereotypic hand movements. The disorder is caused by mutations in the X chromosomal MECP2 a gene encoding methyl CpG-binding protein. It has been associated with disturbances of cerebral folate homeostasis, as well as with speculations on a compromised DNA-methylation. Folinic acid is the stable form of folate. Its derived intermediate 5-MTHF supports the conversion of homocysteine to methionine, the precursor of S-adenosylmethionine (SAM). This in turn donates its methyl group to various acceptors, including DNA, thereby being converted to S-adenosylhomocysteine (SAH). The SAM/SAH ratio reflects the methylation potential. The goal of our study was to influence DNA methylation processes and ameliorate the clinical symptoms in Rett syndrome. Therefore we examined the hypothesis that folinic acid supplementation, besides increasing cerebrospinal fluid (CSF) 5-MTHF (p = 0.003), influences SAM and SAH and their ratio. In our randomized, double-blind crossover study on folinic acid supplementation, ten female Rett patients received both folinic acid and placebo for 1 year each. It was shown that both SAM and SAH levels in the CSF remained unchanged following folinic acid administration (p = 0.202 and p = 0.097, respectively) in spite of a rise of plasma SAM and SAH (p = 0.007; p = 0.009). There was no significant change in the SAM/SAH ratio either in plasma or CSF. The apparent inability of Rett patients to upregulate SAM and SAH levels in the CSF may contribute to the biochemical anomalies of the Rett syndrome. Our studies warrant further attempts to promote DNA methylation in the true region of interest, i.e. the brain.

Brown-Vialetto-Van Laere and Fazio Londe syndrome is associated with a riboflavin transporter defect mimicking mild MADD: a new inborn error of metabolism with potential treatment.

We report on three patients (two siblings and one unrelated) presenting in infancy with progressive muscle weakness and paralysis of the diaphragm. Metabolic studies revealed a profile of plasma acylcarnitines and urine organic acids suggestive of a mild form of the multiple acyl-CoA dehydrogenation defect (MADD, ethylmalonic/adipic acid syndrome). Subsequently, a profound flavin deficiency in spite of a normal dietary riboflavin intake was established in the plasma of all three children, suggesting a riboflavin transporter defect. Genetic analysis of these patients demonstrated mutations in the C20orf54 gene which encodes the human homolog of a rat riboflavin transporter. This gene was recently implicated in the Brown-Vialetto-Van Laere syndrome, a rare neurological disorder which may either present in infancy with neurological deterioration with hypotonia, respiratory insufficiency and early death, or later in life with deafness and progressive ponto-bulbar palsy. Supplementation of riboflavin rapidly improved the clinical symptoms as well as the biochemical abnormalities in our patients, demonstrating that high dose riboflavin is a potential treatment for the Brown-Vialetto-Van Laere syndrome as well as for the Fazio Londe syndrome which is considered to be the same disease entity without the deafness.

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.

Catecholamines profiles at diagnosis: Increased diagnostic sensitivity and correlation with biological and clinical features in neuroblastoma patients.

INTRODUCTION: Neuroblastoma (NBL) accounts for 10% of the paediatric malignancies and is responsible for 15% of the paediatric cancer-related deaths. Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are most commonly analysed in urine of NBL patients. However, their diagnostic sensitivity is suboptimal (82%). Therefore, we performed in-depth analysis of the diagnostic sensitivity of a panel of urinary catecholamine metabolites. PATIENTS AND METHODS: Retrospective study of a panel of 8 urinary catecholamine metabolites (VMA, HVA, 3-methoxytyramine [3MT], dopamine, epinephrine, metanephrine, norepinephrine and normetanephrine [NMN]) from 301 NBL patients at diagnosis. Special attention was given to subgroups, metaiodobenzylguanidine (MIBG) non-avid tumours and VMA/HVA negative patients. RESULTS: Elevated catecholamine metabolites, especially 3MT, correlated with nine out of 12 NBL characteristics such as stage, age, MYCN amplification, loss of heterozygosity for 1p and bone-marrow invasion. The combination of the classical markers VMA and HVA had a diagnostic sensitivity of 84%. NMN was the most sensitive single diagnostic metabolite with overall sensitivity of 89%. When all 8 metabolites were combined, a diagnostic sensitivity of 95% was achieved. Among the VMA and HVA negative patients, were also 29% with stage 4 disease, which usually had elevation of other catecholamine metabolites (93%). Diagnostic sensitivity for patients with MIBG non-avid tumour was improved from 33% (VMA and/or HVA) to 89% by measuring the panel. CONCLUSIONS: Our study demonstrates that analysis of a urinary catecholamine metabolite panel, comprising 8 metabolites, ensures the highest sensitivity to diagnose NBL patients.

New insights in dihydropyrimidine dehydrogenase deficiency: a pivotal role for beta-aminoisobutyric acid?

DPD (dihydropyrimidine dehydrogenase) constitutes the first step of the pyrimidine degradation pathway, in which the pyrimidine bases uracil and thymine are catabolized to beta-alanine and the R-enantiomer of beta-AIB (beta-aminoisobutyric acid) respectively. The S-enantiomer of beta-AIB is predominantly derived from the catabolism of valine. It has been suggested that an altered homoeostasis of beta-alanine underlies some of the clinical abnormalities encountered in patients with a DPD deficiency. In the present study, we demonstrated that only a slightly decreased concentration of beta-alanine was present in the urine and plasma, whereas normal levels of beta-alanine were present in the cerebrospinal fluid of patients with a DPD deficiency. Therefore the metabolism of beta-alanine-containing peptides, such as carnosine, may be an important factor involved in the homoeostasis of beta-alanine in patients with DPD deficiency. The mean concentration of beta-AIB was approx. 2-3-fold lower in cerebrospinal fluid and urine of patients with a DPD deficiency, when compared with controls. In contrast, strongly decreased levels (10-fold) of beta-AIB were present in the plasma of DPD patients. Our results demonstrate that, under pathological conditions, the catabolism of valine can result in the production of significant amounts of beta-AIB. Furthermore, the observation that the R-enantiomer of beta-AIB is abundantly present in the urine of DPD patients suggests that significant cross-over exists between the thymine and valine catabolic pathways.

Etiology of mental retardation in children referred to a tertiary care center: a prospective study.

A prospective assessment following a step-wise protocol in 281 patients with unexplained cognitive delay was used to assess diagnostic possibilities. Diagnostic procedures were complex and required a multidisciplinary approach. One third of diagnoses was established based on clinical history and physical exam only; for another third, clinical history and physical exam provided essential clues for additional investigations; and a third were established by additional investigations only. The likelihood to reach a diagnosis did not depend on the severity of mental retardation. We found that in a tertiary care center, a diagnosis can be established in 1 out of every 2 patients. Clinical history and physical examination are the most important instruments to reach a diagnosis.

Report of two never treated adult sisters with aromatic L-amino Acid decarboxylase deficiency: a portrait of the natural history of the disease or an expanding phenotype?

Two sisters were diagnosed in their adulthood with aromatic L-amino acid decarboxylase (AADC) deficiency (OMIM#608643). They experienced early myasthenia-like manifestations, myoclonic jerks, oculogyric crises, tremors, and developmental delay during childhood; clinical stabilization afterwards; and spontaneous improvement during adolescence and young adulthood. Two novel pathogenic mutations on DDC gene [p.Tyr37Thrfs*5 (c.105delC) and p.F237S (c.710 T>C)] were associated with undetectable enzyme activity in plasma and only a mild reduction of biogenic amines in cerebrospinal fluid (CSF). The increase of both 3-O-methyldopa and 5-hydroxytryptophan on CSF was the most relevant biochemical alteration denoting AADC defect in these subjects. Transdermal rotigotine remarkably improved their gross motor functions and the asthenic status they complained. The present cases broaden the phenotypic spectrum of AADC deficiency and suggest that (1) AADC defect is not a progressive neurological disease and behaves rather as a neurodevelopmental disorder that improves during the second decade of life; (2) treatment-naïve adults can still respond well to neurotransmitter therapy; and (3) the possibility of a mild presentation of AADC deficiency should be considered when examining young adults with asthenic and parkinsonian symptoms.

Phenylketonuria and glycogen storage disease type III in sibs of one family.

Hyperphenylalaninemia result from a block in the conversion of phenylalanine into tyrosine due to a defect in either the enzyme phenylalanine hydroxylase (98% of subjects) or in the metabolism of the cofactor tetrahydrobiopterin. Phenylalanine hydroxylase deficiency is the most common form of inherited hyperphenylalaninemia disorders, with a prevalence between 1/4,000-1/40,000. Glycogen storage disease (GSD) type III is caused by debranching enzyme deficiency of glycogen degradation. The clinical features vary in relation to the localization of the enzyme defect. Two clinical entities exist: a combined hepatic myogenic form (GSD IIIa) and a purely hepatic form (GSD IIIb). The inheritance is autosomal recessive. We describe a Turkish family in which two girls were found to have phenylketonuria, while in two other sisters glycogen storage disease type III was diagnosed. The parents of these children are cousins and they have had 12 children.

The Brown-Vialetto-Van Laere and Fazio Londe syndrome revisited: natural history, genetics, treatment and future perspectives.

The Brown-Vialetto-Van Laere syndrome is a rare neurological disorder which may present at all ages with sensorineural deafness, bulbar palsy and respiratory compromise. Fazio-Londe syndrome is considered to be the same disease entity. Recently it was demonstrated that in some patients the disease is caused by mutations in the SLC52A3 gene which encodes the intestinal (hRFT2) riboflavin transporter. In these patients riboflavin deficiency is the cause of the BVVL/FL syndrome and supplementation of riboflavin proved a life saving treatment. Mutations in the SLC52A2 gene and the SLC52A1 (GPR172B) gene, coding for human riboflavin transporters hRFT3 and hRFT1 have been associated with the BVVL syndrome as well. We performed a review of the literature, with emphasis on the natural history and the effects of treatment in these patients. A total of 35 publications were traced reporting on the clinical presentation of 74 patients who presented before age 18. The most prevalent symptoms were bulbar palsy, hearing loss, facial weakness and respiratory compromise. Death was reported in 28 of the 61 untreated patients, with a very low survival in patients presenting before age 4. All 13 patients who were treated with riboflavin survived, with a strong clinical improvement after days to months of treatment in eight patients. Three patients demonstrated a stable clinical course and treatment was stopped early in two patients. Abnormalities in plasma flavin levels and/or plasma acylcarnitine profiles were observed in some but not in all patients, and also patients with normal plasma flavin levels and acylcarnitine profiles demonstrated a striking clinical improvement on riboflavin supplementation. It is now clear that proper diagnosis requires mutation analysis of all three transporter genes and treatment should be started immediately without first awaiting results of molecular analysis. Clinical improvement may be rapid or gradual over a period of more than 12 months.

Neurodegeneration with Brain Iron Accumulation on MRI: An Adult Case of α-Mannosidosis.

CASE: A 34-year-old woman was referred to our hospital with progressive movement disorders and neurodegeneration with brain iron accumulation and enlargement of the frontal diploe on the MRI. Metabolic testing revealed that she had α-mannosidosis (AMD), a lysosomal storage disorder. BACKGROUND: AMD is a rare genetic disorder that causes α-mannosidase deficiency resulting in lysosomal accumulation of undigested oligosaccharides. The symptoms of AMD consist of facial and skeletal deformities combined with progressive psychiatric and neurological complaints, especially ataxia and mental retardation. Bilateral patellar dislocation and hearing impairment are frequent. DISCUSSION: The movement disorders we found in our patient have not been reported previously, but they are likely late symptoms of this progressive disorder. The iron deposits in the basal ganglia have also not been reported in AMD and are yet of unknown significance. Lysosomal storage disorders, such as AMD, should be considered in patients with progressive neurologic conditions and neurodegeneration with brain iron accumulation on MRI.

The ketogenic diet is well tolerated and can be effective in patients with argininosuccinate lyase deficiency and refractory epilepsy.

Argininosuccinate lyase (ASL) deficiency (MIM 608310, McKusick 207900) is a rare disorder of the urea cycle, which leads to a deficiency of arginine and hyperammonemia. Epilepsy is a frequent complication of this disorder. A ketogenic diet (KD) can be a very effective therapy for refractory epilepsy, and it has been widely used in children. Until now, no experiences with the KD in patients with urea cycle defects have been reported.We present two cases of patients with ASL deficiency and refractory epilepsy who were treated with a KD. In both patients, the KD was initiated during a hospital admission and the fat percentage of the diet was increased to above 90% in five equal steps. In patient 1, during the KD the protein intake was continued as before, and in patient 2 the natural protein was increased with 0,2 g/kg/day while the protein from the amino acid supplement (UCD-2(®), Milupa) was decreased with 0,3 g/kg/day. During and after the introduction of the KD, all biochemical parameters reflecting urea cycle function and ammonia levels were stable in both patients and no signs of derangement were detected. On the KD, patient 1 demonstrated a reduction in seizure frequency of >50%, and an increase in well-being. In patient 2, no effects of the KD on the seizure frequency were noted and after 6 months the KD was discontinued.Concluding, the KD does not cause metabolic derangement, is well tolerated, and can be effective in patients with ASL deficiency who are treated with a protein restriction.

Clinical and electroencephalographic effects of folinic acid treatment in Rett syndrome patients.

Rett syndrome is characterized by the development of stereotypic hand movements and seizures, which are often difficult to treat. Previous studies have shown conflicting results during add-on folinic acid. Here, the authors reevaluate the response to folinic acid in terms of epilepsy control and electroencephalography features. They performed a randomized, placebo-controlled, double-blind crossover trial, with a follow-up of more than 2 years. Twelve girls with Rett syndrome participated, comparable in clinical stage and disease severity. The Rett syndrome patients were given either folinic acid or placebo, for 1 year each. Only 3 girls benefited to some extent: 2 had a reduction and/or decrease in seizures, and all 3 showed some decreased epileptiform activity on electroencephalography during the addition of folinic acid. Despite this, antiepileptic drugs were adjusted. Because the effect of added folinic acid was limited and did not prevent antiepileptic drug increase, the authors do not recommend adding on folinic acid in Rett syndrome girls with epilepsy.

Persistent decline in estimated but not measured glomerular filtration rate on tenofovir may reflect tubular rather than glomerular toxicity.

BACKGROUND: Tenofovir disoproxil fumarate (TDF) has been associated with proximal renal tubulopathy and reduction in estimated glomerular filtration rate (eGFR), without accounting for the tubular secretion of creatinine. METHODS: A substudy was performed among 19 participants of a randomized 48-week trial, comparing continuing first-line zidovudine/lamivudine (ZDV/3TC) with switching to TDF/emtricitabine (FTC). GFR was measured with [(125)I]-iothalamate (mGFR) and effective renal plasma flow (ERPF) with [(131)I]-hippuran. eGFR and tubular effects were assessed using plasma and urine samples. RESULTS: Of the 19 patients, 18 were men, 15 whites, mean (SD) age 46.0 (8.9) years, plasma HIV-1 RNA less than 50 copies/ml in all. After 48 weeks, eGFR using Cockcroft-Gault equation and ERPF, but not mGFR, had significantly decreased, and urinary α1-microglobulin/creatinine and microalbumin/creatinine significantly increased in patients on TDF. Although phosphate metabolism on TDF was affected at week 4, differences between groups disappeared during follow-up. CONCLUSION: Replacing ZDV/3TC with TDF/FTC in this limited sample of virologically suppressed HIV-1-infected adults was associated with mild persistent tubular but not glomerular dysfunction over 48 weeks. The observed persistent decrease in Cockcroft-Gault-based eGFR, but not mGFR, rather than being indicative of glomerular dysfunction may be explained by TDF inhibiting tubular creatinine excretion.

Plasma and erythrocyte fatty acid patterns in patients with recurrent depression: a matched case-control study.

BACKGROUND: The polyunsaturated fatty acid (PUFA) composition of (nerve) cell membranes may be involved in the pathophysiology of depression. Studies so far, focussed mainly on omega-3 and omega-6 PUFAs. In the present study, saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and PUFAs of the omega-3, -6 and -9 series in plasma and erythrocytes of patients with recurrent major depressive disorder (MDD-R) were compared with controls. METHODOLOGY AND PRINCIPAL FINDINGS: We carried out a case-control study. The sample consisted of 137 patients with MDD-R and 65 matched non-depressed controls. In plasma and erythrocytes of patients with MDD-R the concentrations of most of the SFAs and MUFAs, and additionally erythrocyte PUFAs, all with a chain length > 20 carbon (C) atoms, were significantly lower than in the controls. In contrast, the concentrations of most of the shorter chain members (< or = 18C) of the SFAs and MUFAs were significantly higher in the patients. Estimated activities of several elongases in plasma of patients were significantly altered, whereas delta-9 desaturase activity for C14:0 and C18:0 was significantly higher. CONCLUSIONS/SIGNIFICANCE: The fatty acid status of patients with MDD-R not only differs with regard to omega-3 and omega-6 PUFAs, but also concerns other fatty acids. These alterations may be due to: differences in diet, changes in synthesizing enzyme activities, higher levels of chronic (oxidative) stress but may also result from adaptive strategies by providing protection against enhanced oxidative stress and production of free radicals.

Clinical, biochemical and genetic findings in two siblings with a dihydropyrimidinase deficiency.

Dihydropyrimidinase (DHP) is the second enzyme of the pyrimidine degradation pathway and it catalyses the ring opening of 5,6-dihydrouracil and 5,6-dihydrothymine to N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid, respectively. To date, only nine individuals have been reported suffering from a complete DHP deficiency. We report two siblings presenting with strongly elevated levels of 5,6-dihydrouracil and 5,6-dihydrothymine in plasma, cerebrospinal fluid and urine. One of the siblings had a severe delay in speech development and white matter abnormalities, whereas the other one was free of symptoms. Analysis of the DHP gene (DPYS) showed that both patients were compound heterozygous for the missense mutation 1078T>C (W360R) in exon 6 and a novel missense mutation 1235G>T (R412M) in exon 7. Heterologous expression of the mutant enzymes in Escherichia coli showed that both missense mutations resulted in a mutant DHP enzyme without residual activity. Analysis of the crystal structure of eukaryotic DHP from the yeast Saccharomyces kluyveri and the slime mold Dictyostelium discoideum suggests that the W360R and R412M mutations lead to structural instability of the enzyme which could potentially impair the assembly of the tetramer.

Sepiapterin reductase deficiency an autosomal recessive DOPA-responsive dystonia.

The diagnosis of a 14-year-old girl with a new homoallelic mutation in the sepiapterin reductase (SR) gene is reported. Initially she presented at the age of 2 with hypotonia and mild cognitive developmental delay, and was diagnosed as having mild methylmalonic aciduria, which was recently identified as methylmalonylCoA racemase deficiency, a new defect in valine-isoleucine metabolism. After a 12-year progression of her neurologic condition, which had made her wheelchair-bound at the age of 6, dystonia with diurnal variation had become apparent. At the age of 14 this finding led to rapid diagnosis of SR deficiency. The diagnostic approach with CSF neurotransmitter and pterins analysis and combined phenylalanine/BH(4) loading test, and finally measurement of sepiapterin in CSF is illustrative for the diagnosis of SR deficiency. As in all other patients with this new defect, very low levels of homovanillic acid and 5-hydroxyindoleacetic acid and high levels of biopterin and sepiapterin in the CSF are the diagnostic hallmark. The girl improved dramatically on treatment with L-DOPA and 5-hydroxytryptophan. The initial diagnosis of methylmalonic aciduria may afterwards be considered to have not significantly contributed to her clinical condition and only has led to a long delay of the clinically relevant diagnosis of SR deficiency. Although the clinical condition of this recently recognized autosomal recessive defect in pterin metabolism is complex and many symptoms can occur in variable severity and time of onset, dystonia with diurnal variation is a characteristic finding, as shown in nearly all patients described so far. The rapid and favourable response on treatment with L-DOPA warrants the classification of SR deficiency as another autosomal recessive type of DOPA-responsive dystonia (DRD). This classification is important to improve the awareness of clinicians that more than one metabolic defect can underlie the phenotype of a DOPA-responsive dystonic disorder and that dystonia should always trigger a rapid diagnosis of the underlying neurotransmitter synthesis defect, in view of the excellent treatability of a DRD.