Defining tetrahydrobiopterin responsiveness in phenylketonuria: Survey results from 38 countries.

BACKGROUND: A subset of patients with phenylketonuria benefit from treatment with tetrahydrobiopterin (BH4), although there is no consensus on the definition of BH4 responsiveness. The aim of this study therefore was to gain insight into the definitions of long-term BH4 responsiveness being used around the world. METHODS: We performed a web-based survey targeting healthcare professionals involved in the treatment of PKU patients. Data were analysed according to geographical region (Europe, USA/Canada, other). RESULTS: We analysed 166 responses. Long-term BH4 responsiveness was commonly defined using natural protein tolerance (95.6%), improvement of metabolic control (73.5%) and increase in quality of life (48.2%). When a specific value for a reduction in phenylalanine concentrations was reported (n = 89), 30% and 20% were most frequently used as cut-off values (76% and 19% of respondents, respectively). When a specific relative increase in natural protein tolerance was used to define long-term BH4 responsiveness (n = 71), respondents most commonly reported cut-off values of 30% and 100% (28% of respondents in both cases). Respondents from USA/Canada (n = 50) generally used less strict cut-off values compared to Europe (n = 96). Furthermore, respondents working within the same center answered differently. CONCLUSION: The results of this study suggest a very heterogeneous situation on the topic of defining long-term BH4 responsiveness, not only at a worldwide level but also within centers. Developing a strong evidence- and consensus-based definition would improve the quality of BH4 treatment.

The challenges of managing coexistent disorders with phenylketonuria: 30 cases.

INTRODUCTION: The few published case reports of co-existent disease with phenylketonuria (PKU) are mainly genetic and familial conditions from consanguineous marriages. The clinical and demographic features of 30 subjects with PKU and co-existent conditions were described in this multi-centre, retrospective cohort study. METHODS: Diagnostic age of PKU and co-existent condition, treatment regimen, and impact of co-existent condition on blood phenylalanine (Phe) control and PKU management were reported. RESULTS: 30 patients (11 males and 19 females), with PKU and a co-existent condition, current median age of 14 years (range 0.4 to 40 years) from 13 treatment centres from Europe and Turkey were described. There were 21 co-existent conditions with PKU; 9 were autoimmune; 6 gastrointestinal, 3 chromosomal abnormalities, and 3 inherited conditions. There were only 5 cases of parental consanguinity. Some patients required conflicting diet therapy (n=5), nutritional support (n=7) and 5 children had feeding problems. There was delayed diagnosis of co-existent conditions (n=3); delayed treatment of PKU (n=1) and amenorrhea associated with Grave's disease that masked a PKU pregnancy for 12 weeks. Co-existent conditions adversely affected blood Phe control in 47% (n=14) of patients. Some co-existent conditions increased the complexity of disease management and increased management burden for patients and caregivers. CONCLUSIONS: Occurrence of co-existent disease is not uncommon in patients with PKU and so investigation for co-existent disorders when the clinical history is not completely consistent with PKU is essential. Integrating care of a second condition with PKU management is challenging.

Sapropterin dihydrochloride: a new drug and a new concept in the management of phenylketonuria.

Phenylketonuria (PKU) is characterized by persistent hyperphenylalaninemia, due to mutations in the gene coding for phenylalanine hydroxylase (PAH). If untreated, patients develop profound mental retardation. The principal treatment for PKU is lifelong dietary phenylalanine restriction, requiring the administration of special phenylalanine-free protein supplements. Adhering to the diet is burdensome, and poor compliance and control of blood phenylalanine are common, especially in adolescents and adults. A subset of patients, particularly those with milder forms of PKU, shows a clinically significant reduction in blood phenylalanine when treated with pharmacological doses of tetrahydrobiopterin, the cofactor of PAH. A tablet formulation of sapropterin dihydrochloride is approved for therapeutic use in Europe and the USA. Clinical trials have demonstrated durable reductions in blood phenylalanine, and/or increased dietary phenylalanine tolerance, in some patients with hyperphenylalaninemia due to PKU. Although further data are needed, especially with regard to long-term neuropsychological outcomes or possible use in pregnancy, sapropterin appears to represent a useful addition to the management of PKU.

Significance of genotype in tetrahydrobiopterin-responsive phenylketonuria.

BACKGROUND: The value of genotyping to identify tetrahydrobiopterin-responsive (BH(4)-responsive) patients with phenylalanine hydroxylase (PAH) deficiency is a matter of debate. METHODS: We reviewed 250 cases of patients with PAH deficiency, using published data from 198 cases and unpublished data from 52 cases of patients attending our own clinic. Patients underwent analyses for BH(4) load and genetic mutations. Partial and full BH(4) responses were defined as a 10-29% decrease and a >or=30% decrease from baseline in blood phenylalanine levels, respectively. BH(4)-responsive alleles were identified from BH(4)-responsive patients as either homozygous for a specific allele or compound heterozygous for that allele with a null mutation. RESULTS: Most inconsistencies between observed genotype and BH(4) response were associated with mutations in the regulatory domain of PAH (p.R68S, p.I65T, p.L48S and p.F39C), where 20/62 alleles (32.2%) were non-responsive. In the catalytic domain (mutations p.Y414C, p.R261Q, p.E390G, p.A300S, p.R241C, p.A403V and p.V388M), only 8/125 alleles (6.4%) were non-responsive. Seven patients had a genotype with two BH(4)-responsive alleles resulting in no response or only a partial response to BH(4). Ten patients had identical genotypes but inconsistent responses in BH(4) load. CONCLUSIONS: These results show that BH(4) non-responsiveness is associated with genotype. However, patients with mutations in the regulatory domain show inconsistent results. In patients with two responsive alleles, non-responsiveness may be related to negative inter-allelic complementation. In patients with the same genotype and inconsistent results for BH(4) load, external factors such as intestinal absorption of BH(4), catabolic conditions or other genetic factors may be responsible. Further in vitro studies are necessary to clarify the genotype-phenotype correlation in patients with BH(4)-responsive PKU.

[Propionic acidemia and sensorineural hearing loss: is there a connection at the molecular genetics level?]. / Propionazidämie und Schallempfindungsschwerhörigkeit: Gibt es eine molekulargenetische Basis?

CURRENT KNOWLEDGE: Propionic acidemia is caused by a gene defect leading to malfunction of the enzyme propionyl-CoA carboxylase (PCC) and in turn to a pathologic accumulation of propionic acid. Many mutations have been found at the molecular genetic level over the past 20 years, and their implications for the limitation of enzyme activity of PCC in propionic acidemia are discussed. SCIENTIFIC QUESTION AND AIMS OF THE STUDY: As an elevated incidence of deafness has been observed in patients with propionic acidemia, the question arises of whether mutations primarily responsible for this disease could also be the underlying cause for a genetic form of deafness. METHODS AND RESULTS: As well as a standard pure tone audiogram, a pedigree was elaborated and DNA isolated for each family concerned. In one family several subjects displayed mutations of both the PCCA and the PCCB -subunits; these included only one girl whose phenotype was affected, however. CONCLUSIONS: Mutation of the PCCB subunit p.R113X has not previously been mentioned in the literature. According to our present knowledge no connection can be assumed between either of the two mutations and the severe sensorineural hearing loss.

Effects of cholesterol and simvastatin treatment in patients with Smith-Lemli-Opitz syndrome (SLOS).

Smith-Lemli-Opitz syndrome (SLOS) is a malformation syndrome caused by deficiency of 7-dehydrocholesterol reductase catalysing the last step of cholesterol biosynthesis. This results in an accumulation of 7- and 8-dehydrocholesterol (7 + 8-DHC) and, in most patients, a deficiency of cholesterol. Current therapy consists of dietary cholesterol supplementation, which raises plasma cholesterol levels, but clinical effects have been reported in only a few patients. Hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors were shown to reduce 7 + 8-DHC levels and increase cholesterol concentrations in two small trials with divergent clinical outcome. This retrolective study evaluates the effects of cholesterol only and of cholesterol plus the HMG-CoA reductase inhibitor simvastatin on plasma sterols in 39 SLOS patients and on anthropometric measures in 20 SLOS patients. Cholesterol as well as additional simvastatin decreased the plasma (7 + 8-DHC)/cholesterol ratio. However, the mechanism leading to the decreasing ratio was different. Whereas it was due to an increasing cholesterol concentration in the cholesterol-only cohort, a decreasing 7 + 8-DHC concentration was demonstrated in the cohort receiving additional simvastatin. We could not confirm a positive effect of simvastatin treatment on anthropometric measures or behaviour, as previously reported.

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.

CblC/D defect combined with haemodynamically highly relevant VSD.

An infant with combined methylmalonic aciduria and homocystinuria (cblC/D defect) presented with significant VSD. She underwent successful cardiac surgery at 53 days.

Ventricular septal defect closure in a neonate with combined methylmalonic aciduria/homocystinuria.

Methylmalonic acidemia with associated homocystinuria is a rare inborn error of amino acid metabolism affecting energy supply on the cellular level. Its effects on recovery from surgically induced organ ischemia are largely unknown. We report the successful closure of a nonrestrictive ventricular septal defect by following a normothermic strategy combined with ample metabolic substrate supply.

Long-term treatment with sodium phenylbutyrate in ornithine transcarbamylase-deficient patients.

Ornithine transcarbamylase deficiency is a very heterogeneous urea cycle disorder resulting in hyperammonemia with various presentations from the neonatal period through adulthood. We performed a retrospective study in nine patients (four male/five female, age at diagnosis ranging from 6 days to 14 years) to evaluate the safety and efficacy of sodium phenylbutyrate (Ammonaps) in long-term treatment. All patients were diagnosed by DNA mutational analysis and/or liver enzyme measurement. They had previously been treated with sodium benzoate (median dose 248 mg/kg/day; range 106-275) and low protein diet (median 0.84 g/kg/day) and were switched to sodium phenylbutyrate (median dose of 352 mg/kg/day) at 8.9 and 4.9 years of age (median) in males and females, respectively. We analyzed clinical and biochemical data and the median follow-up duration was 26 months. During that time, there were no hyperammonemic episodes requiring hospitalization. Median plasma ammonia and glutamine levels were 30 and 902 micromol/L, respectively. Total protein intake could be increased to 0.95 g/kg/day after 18 months. No side effects related to therapy were observed. Further prospective studies should be performed to define the optimal dosage of sodium phenylbutyrate and the requirements for protein diet at different ages.

Outcome of tyrosinaemia type III.

Tyrosinaemia type III is a rare disorder caused by a deficiency of 4-hydroxyphenylpyruvate dioxygenase, the second enzyme in the catabolic pathway of tyrosine. The majority of the nine previously reported patients have presented with neurological symptoms after the neonatal period, while others detected by neonatal screening have been asymptomatic. All have had normal liver and renal function and none has skin or eye abnormalities. A further four patients with tyrosinaemia type III are described. It is not clear whether a strict low tyrosine diet alters the natural history of tyrosinaemia type III, although there remains a suspicion that treatment may be important, at least in infancy.

Final intelligence in late treated patients with phenylketonuria.

UNLABELLED: Despite neonatal screening programmes, there is still a number of patients with phenylketonuria who are not diagnosed and start treatment late. The question in this study was to evaluate which factors will contribute, other than the quality and duration of dietary treatment, to final outcome in late treated patients with phenylketonuria. We retrospectively analysed the data of 40 patients with phenylketonuria, of whom 2 patients at 35 and 24 years of age had a normal IQ despite never being treated. In 38 patients starting dietary treatment between 0.7 and 7 years of age, mean IQ/DQ at diagnosis was 52.7 (SD = 16) (mean age 2.5 years), final IQ (mean age 33.5 years) was 79.0 (SD = 16), the difference was highly significant (P < 0.0001). Important factors for the final intelligence in adult late treated patients with phenylketonuria were onset (r = -0.46, P < 0.009) and DQ/IQ (r = 0.51, P < 0.002) when dietary treatment was started. Thus, in late treated patients with phenylketonuria, in addition to the quality and duration of treatment, the outcome is mainly influenced by the age of starting treatment and also by the intellectual status of the patient. In one of the two patients with normal intelligence, nuclear magnetic resonance spectroscopy showed that brain phenylalanine was undetectable even though blood phenylalanine was 30 mg/dl. A second metabolic disorder may protect these patients from severe brain damage. CONCLUSION: These data indicate that brain damage in untreated or late treated patients with phenylketonuria is influenced by various genetic factors.

Three-year-old girl with partial trisomy 4p and partial monosomy 8p with resemblance to Brachmann-de Lange syndrome--another locus for Brachmann-de Lange syndrome on 4p?

We describe a 3-year-old girl with partial trisomy 4p and partial monosomy 8p who had prenatal and postnatal growth retardation, mental retardation, no speech development, mild synophrys, hirsutism, apparently low-set ears, dysphonic hoarse voice, hyperactivity, and small hands with proximal placement of the thumbs. She had recurrent lung infections, due to earlier aspiration and immune deficiency (chronic granulomatous disease). Cytogenetic findings in this and other cases with suggestive phenotype may point to an additional locus for Brachmann-de Lange phenotype.

Diagnosis of mitochondrial trifunctional protein deficiency in a blood spot from the newborn screening card by tandem mass spectrometry and DNA analysis.

Trifunctional protein (TFP) plays a significant role in the mitochondrial beta-oxidation of long-chain fatty acids. Its deficiency impairs the energy generating function of this pathway and causes hypoketotic hypoglycemia once hepatic glycogen stores are depleted. A Reye-like syndrome, cardiomyopathy, and sudden death may follow. The diagnosis is based on demonstration of significantly decreased enzyme activity of at least two of the three involved enzymes in fibroblasts. The possibility of prospective diagnosis of TFP deficiency by newborn screening using tandem mass spectrometry (MS/MS) has not been evaluated. We report the postmortem diagnosis of a male newborn, who suffered sudden death at 2 wk of age, and his younger sister, who died of cardiomyopathy complicated by acute heart failure at the age of 6 mo, after she had acquired a common viral infection. Blood spots from the original newborn screening cards were the only remaining material from the patients. Analysis by MS/MS revealed acylcarnitine profiles consistent with either TFP or long-chain 3-hydroxyacyl coenzyme A dehydrogenase (LCHAD) deficiency. To prove the diagnosis, the alpha- and beta-subunit genes coding for TFP were examined. The patients were compound heterozygous for a 4-bp-deletion and an a-->g missense mutation, both in the same exon 3 donor consensus splice site. This is the first report of the diagnosis of TFP deficiency using blood spots obtained for newborn screening and suggests that TFP deficiency may be detectable by prospective newborn screening using MS/MS.

Rationale for the German recommendations for phenylalanine level control in phenylketonuria 1997.

UNLABELLED: Treatment of hyperphenylalaninaemias due to phenylalanine hydroxylase deficiency with a low phenylalanine (Phe) diet is highly successful in preventing neurological impairment and mental retardation. There is consensus that, for an optimal outcome, treatment should start as early as possible, and that strict blood Phe level control is of primary importance during the first years of life, but for adolescent and adult patients international treatment recommendations show a great variability. A working party of the German Working Group for Metabolic Diseases has evaluated research results on IQ data, speech development, behavioural problems, educational progress, neuropsychological results, electroencephalography, magnetic resonance imaging, and clinical neurology. Based on the actual knowledge, recommendations were formulated with regard to indication of treatment, differential diagnosis, and Phe level control during different age periods. The development of the early-and-strictly-treated patient in middle and late adulthood still remains to be investigated. Therefore, the recommendations should be regarded as provisional and subject to future research. Efficient treatment of phenylketonuria has to go beyond recommendations for blood Phe level control and must include adequate dietary training, medical as well as psychological counselling of the patient and his family, and a protocol for monitoring outcome. CONCLUSIONS: Early-and-strictly-treated patients with phenylketonuria show an almost normal development. During the first 10 years treatment should aim at blood Phenylalanine levels between 40 and 240 micromol/L. After the age of 10, blood phenylalanine level control can be gradually relaxed. For reasons of possible unknown late sequelae, all patients should be followed up life-long.

Early clinical manifestation of glutaric aciduria type I and nephrotic syndrome during the first months of life.

We describe a male patient with glutaric aciduria type I which had already presented during the neonatal period with therapy-resistant seizures. In the course of the disease, he also developed choreoathetosis and dystonia. The disease was associated with nephrotic syndrome. Renal histology showed signs of a glomerular disorder with shrinking of glomerular tufts, increase in mesangial matrix, proliferation of extracapillary epithelial cells and formation of larger epithelial crescents. The child died at 22 weeks of age due to end-stage renal failure. This report illustrates an unusual and early clinical manifestation of glutaric aciduria type I and a hitherto unknown association with nephrotic syndrome in early childhood.

Phenylalanine hydroxylase genotypes, predicted residual enzyme activity and phenotypic parameters of diagnosis and treatment of phenylketonuria.

The interdependence of the predicted in vitro residual enzyme activity (PRA), as deduced from the complete genotypes of 64 hyperphenylalaninaemic patients, and parameters for diagnosis of hyperphenylalaninaemic disorders, the fluctuation of the phyenlylalanine (Phe) values during treatment, long-term dietary control during treatment, and a parameter for the outcome of therapy (IQ) was investigated by correlation analysis. A highly significant correlation was found between the PRA and diagnostic parameters, as well as the fluctuation of the Phe values during treatment. Significant correlations were also observed between the parameter describing the fluctuation of the Phe values and the IQ, as well as between the quality of dietary control and IQ. The PRA is a valuable tool for the differential diagnosis of hyperphenylalaninaemic disorders and for the prediction of one aspect of the course of the disease which is related to the intellectual outcome of therapy. The quality of dietary control was independent of the genotype, indicating that the outcome of therapy can be successfully manipulated in spite of the genetic make-up.