Bone Status in Patients with Phenylketonuria: A Systematic Review.

Phenylketonuria (PKU) is the most common inborn error of amino acid metabolism. Although dietary and, in some cases, pharmacological treatment has been successful in preventing intellectual disability in PKU patients who are treated early, suboptimal outcomes have been reported, including bone mineral disease. In this systematic review, we summarize the available evidence on bone health in PKU patients, including data on bone mineral density (BMD) and bone turnover marker data. Data from cohort and cross-sectional studies of children and adults (up to 40 years of age) were obtained by searching the MEDLINE and SCOPUS databases following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. For each selected study, quality assessment was performed applying the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS I) tool. We found that mean BMD was lower in PKU patients than in reference groups, but was within the normal range in most patients when expressed as Z-score values. Furthermore, data revealed a trend towards an imbalance between bone formation and bone resorption, favoring bone removal. Data on serum levels of minerals and hormones involved in bone metabolism were very heterogeneous, and the analyses were inconclusive. Clinical trials that include the analysis of fracture rates, especially in older patients, are needed to gather more evidence on the clinical implications of lower BMD in PKU patients.

Neurocognitive functioning in adults with phenylketonuria: Report of a 10-year follow-up.

BACKGROUND: The long-term prognosis of early treated phenylketonuria (PKU) is still under discussion. Aim of this controlled long-term study was to assess the neurological and neuropsychological outcome in adult patients with early-treated PKU. METHODS: We investigated 35 patients with early-treated classical PKU aged 29 to 51 years (mean age 41 years) and 18 healthy controls matched for age and socioeconomic status. Patients and controls were assessed for their intelligence quotient (IQ), attention and information-processing abilities. Magnetic resonance imaging (MRI) of the brain was performed in all patients. Neuropsychological assessments and MRI were repeated at a five-year and a ten-year follow-up. RESULTS: In the entire interval IQ, information processing and attention of patients and controls remained constant. At both follow-up assessment times the IQ scores were significantly lower in patients compared to controls. Older adult patients (> 42 years) showed poorer information processing and attention at both assessment times compared to young adult patients (< 42 years) and controls. IQ, information processing and attention showed no correlation to imaging results. IQ, however, was significantly correlated to blood phenylalanine (Phe) levels in patients´ childhood and adolescence, and Phe levels had been higher in the adolescent years of older adult patients. CONCLUSIONS: Cognitive performance in adult patients with early-treated PKU does not seem to deteriorate in a ten-year interval. Neuropsychological assessment in adults with PKU revealed neurocognitive impairment particularly in older adult patients. This seems to refer to an early relaxation of diet that was recommended when the older patients were adolescents. Results indicate a benefit of dietary control during adolescence in PKU.

Phenylketonuria - Genetics Home Reference

A página traz informações em inglês sobre a fenilcetonúria: doença genética, causada pela ausência ou pela diminuição da atividade de uma enzima do fígado, que transforma a fenilalanina (aminoácido presente nas proteínas) em outro aminoácido chamado tirosina.

Molecular genetics and diagnosis of phenylketonuria: state of the art.

Detection of individuals with phenylketonuria (PKU), an autosomal recessively inherited disorder in phenylalanine degradation, is straightforward and efficient due to newborn screening programs. A recent introduction of the pharmacological treatment option emerged rapid development of molecular testing. However, variants responsible for PKU do not all suppress enzyme activity to the same extent. A spectrum of over 850 variants, gives rise to a continuum of hyperphenylalaninemia from very mild, requiring no intervention, to severe classical PKU, requiring urgent intervention. Locus-specific and genotypes database are today an invaluable resource of information for more efficient classification and management of patients. The high-tech molecular methods allow patients' genotype to be obtained in a few days, especially if each laboratory develops a panel for the most frequent variants in the corresponding population.

Cost-benefit analysis of hyperphenylalaninemia due to 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency: for consideration of expanded newborn screening in Hong Kong.

OBJECTIVES: To evaluate the cost-benefit of implementing an expanded newborn screening programme for hyperphenylalaninemias due to 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency in Hong Kong. SETTING: Regional public hospitals in Hong Kong providing care for cases of inborn errors of metabolism. METHODS: Implementational and operational costs of a new expanded mass spectrometry-based newborn screening programme were estimated. Data on various medical expenditures for the mild and severe phenotypic subtypes were gathered from a case cohort diagnosed with PTPS deficiency from 2001 to 2009. Local incidence from a previously published study was used. RESULTS: Implementation and operational costs of an expanded newborn screening programme in Hong Kong were estimated at HKD 10,473,848 (USD 1,342,801) annually. Assuming a birthrate of 50,000 per year and an incidence of 1 in 29,542 live births, the medical costs and adjusted loss of workforce per year would be HKD 20,773,207 (USD 2,663,232). Overall the annual savings from implementing the programme would be HKD 9,632,750 (USD 1,234,968). CONCLUSIONS: Our estimates show that implementation of an expanded newborn screening programme in Hong Kong is cost-effective, with a significant annual saving for public expenditure.

Recommendations for the nutrition management of phenylalanine hydroxylase deficiency.

The effectiveness of a phenylalanine-restricted diet to improve the outcome of individuals with phenylalanine hydroxylase deficiency (OMIM no. 261600) has been recognized since the first patients were treated 60 years ago. However, the treatment regime is complex, costly, and often difficult to maintain for the long term. Improvements and refinements in the diet for phenylalanine hydroxylase deficiency have been made over the years, and adjunctive therapies have proven to be successful for certain patients. Yet evidence-based guidelines for managing phenylalanine hydroxylase deficiency, optimizing outcomes, and addressing all available therapies are lacking. Thus, recommendations for nutrition management were developed using evidence from peer-reviewed publications, gray literature, and consensus surveys. The areas investigated included choice of appropriate medical foods, integration of adjunctive therapies, treatment during pregnancy, monitoring of nutritional and clinical markers, prevention of nutrient deficiencies, providing of access to care, and compliance strategies. This process has not only provided assessment and refinement of current nutrition management and monitoring recommendations but also charted a direction for future studies. This document serves as a companion to the concurrently published American College of Medical Genetics and Genomics guideline for the medical treatment of phenylalanine hydroxylase deficiency.

Undiagnosed phenylketonuria in parents of phenylketonuric patients, is it worthwhile to be checked?

In our phenylketonuria (PKU) cohort of 120 patients, we uncovered a couple of cases of undiagnosed mild phenylketonuria (mPKU)/hyperphenylalaninemia (mHPA) in maternal parents of the PKU cohort. This finding prompted us to evaluate the risk of either mild phenylketonuria or mild hyperphenylalaninemia in the parent population whose children were diagnosed with hyperphenylalaninemia (HPA). Taking into account the phenylalanine hydroxylase (PAH) mutation carrier frequency and the PAH mild mutation rate, we estimated that the prevalence of the parental mPKU/mHPA varied widely, from 1/74 in Turkey to 1/708 in Lithuania. The benefits of the parental detection procedure described here are the prevention of further maternal PKU syndrome, the follow-up of the newly detected patients and the accuracy of the genetic counseling provided to these families. This very simple procedure should be incorporated into neonatal PKU management of the hospitals in countries where a routine systematic neonatal screening is operational.

Evaluación del estado de salud en pacientes con fenilcetonuria / Assessment of the health status of patients with phenylketonuria

Introducción: la fenilcetonuria es el más conocido de todos los errores congénitos del metabolismo. Su detección precoz y una dieta baja en fenilalanina pueden prevenir el retraso mental en los pacientes. Objetivo: evaluar el impacto del programa de prevención precoz de fenilcetonuria en la provincia de Holguín, en el periodo de enero de 1986 a octubre de 2012. Métodos: se realizó un estudio descriptivo retrospectivo en los niños atendidos en la consulta de fenilcetonuria del Hospital Pediátrico de Holguín. El universo estuvo constituido por los 12 pacientes con el diagnóstico de fenilcetonuria. La información se obtuvo a través de las historias clínicas. Se evaluó el control metabólico mediante los valores de fenilalanina sérica registrados en las historias clínicas, el estado nutricional se valoró mediante las tasas de percentiles establecidas en Cuba y el coeficiente intelectual se analizó mediante test psicométricos. Resultados: el 66,6 por ciento(8 de los pacientes) presentó un control metabólico bueno, y 7 para un 58,3 por ciento un intelecto normal. De los pacientes diagnosticados antes de 1986, 3 presentan un retardo mental ligero (42,9 por ciento) y el 28,6 por ciento está incapacitado (2). El 100 por ciento de los diagnosticados por programa presentan un intelecto normal y 5 no presentan síntomas. Estudian 4 para un 80 por ciento. El 83,3 por ciento de los pacientes estudiados son eutróficos (10). Conclusiones: el programa de diagnóstico precoz ha permitido que el estado de salud de los pacientes fenilcetonúricos mejore en cuantía significativa, con una estabilidad en el control metabólico y una integración apreciable a la sociedad

Introduction: phenylketonuria is the most recognized congenital metabolic error. Its early detection and low phwnylalanine diet can prevent mental retardation in these patients. Objective: to evaluate the impact of the early phenylketonuria prevention program in Holguin province from January 1986 to October 2012. Methods: a retrospective descriptive study was made in children who were assisted at the phenylketonuria department of pediatric hospital in Holguin province. The universe of study was 12 patients diagnosed with phenylketonuria. The medical histories provided the necessary information. The metabolic control was evaluated through the serum phanylalanin figures recorded in the medical history, the nutritional status was assessed according to the percentile rates set in Cuba and the intellect coefficient was analyzed with psychometric tests. Results: in this group, 66.6 percent (8 patients) presented good metabolic control and 58.3 percent (7) showed normal intellect. Of the patients diagnosed with the disease before 1986, three (42.9 percent ) suffered mild mental retardation and two (28.6 percent) were disabled. All the patients diagnosed by this program showed normal intellect and 5 had no symptoms. Four were studying for 80 percent. Of the studied patients, 83.3 percent (10) were eutrophic. Conclusions: the early diagnosis program has allowed the significant improvement of the health status of the phenylketonuric patients, with stable metabolic control and noticeable integration to the society

[Maternal phenylketonuria]. / Maternális phenylketonuria.

Elevated maternal phenylalanine levels during pregnancy are teratogenic, and may result in embryo-foetopathy, which could lead to stillbirth, significant psychomotor handicaps and birth defects. This foetal damage is known as maternal phenylketonuria. Women of childbearing age with all forms of phenylketonuria, including mild variants such as hyperphenylalaninaemia, should receive detailed counselling regarding their risks for adverse foetal effects, optimally before contemplating pregnancy. The most assured way to prevent maternal phenylketonuria is to maintain the maternal phenylalanine levels within the optimal range already before conception and throughout the whole pregnancy. Authors review the comprehensive programme for prevention of maternal phenylketonuria at the Metabolic Center of Budapest, they survey the practical approach of the continuous maternal metabolic control and delineate the outcome of pregnancies of mothers with phenylketonuria from the introduction of newborn screening until most recently.

Extremely high phenylalanine levels in a newborn on parenteral nutrition: phenylketonuria in the neonatal intensive care unit.

A 1890-g newborn on total parenteral nutrition (TPN) had phenylalanine levels reaching 4164 µM indicating phenylketonuria (PKU). Review of 64 PKU cases from the California Newborn Screening Program disclosed another newborn diagnosed while on TPN. Phenylalanine levels rose five times faster with TPN, as estimated from rates in these infants. Thus, TPN use is associated with very high phenylalanine levels in newborns with PKU. When starting TPN soon after birth (for example, on day 1), early detection of PKU-by newborn screening 12 to 24 h after infusions are begun-should be helpful in limiting exposures to toxic levels of phenylalanine.

Blood phenylalanine control in phenylketonuria: a survey of 10 European centres.

BACKGROUND: Only limited data are available on the blood phenylalanine (Phe) concentrations achieved in European patients with phenylketonuria (PKU) on a low-Phe diet. OBJECTIVE: A survey was conducted to compare blood Phe control achieved in diet-treated patients with PKU of different age groups in 10 European centres. METHODS: Centres experienced in the management of PKU from Belgium, Denmark, Germany, Italy, The Netherlands, Norway, Poland, Spain, Turkey and the United Kingdom provided retrospective audit data of all patients with PKU treated by diet over a 1-year period. Standard questions were used to collect median data on blood Phe concentrations, percentage of blood Phe concentrations below upper target reference ranges and frequency of blood Phe sampling. RESULTS: Data from 1921 patients on dietary management were included. Blood Phe concentrations were well controlled and comparable across centres in the early years of life. The percentages of blood Phe concentrations meeting each centre's local and national target ranges were 88% in children aged up to 1 year, 74% for 1-10 years, 89% for 11-16 years and 65% for adults (>16 years). The frequency of home blood sampling, compared with local and national recommendations for monitoring Phe concentrations, appeared to decline with age (from approximately 100% in infancy to 83% in teenagers and 55% in adults). CONCLUSIONS: Although blood Phe control generally deteriorated with age, some improvement was observed in adolescent years across the 10 European centres. The blood Phe control achieved seemed comparable in many of the European centres irrespective of different dietary treatments or national policies.

Cost effectiveness of establishing a neonatal screening programme for phenylketonuria in Libya.

BACKGROUND: Inborn errors of metabolism (IEM) are a significant cause of morbidity and mortality in North Africa and the Middle East. With the evident success of neighbouring countries in initiating neonatal screening for IEM, the Libyan Authorities are now considering introducing neonatal screening for phenylketonuria (PKU) in Libya in the first instance, with the prospect of expanding the programme to cover other IEM in the future. OBJECTIVE: To estimate the cost effectiveness of neonatal screening for PKU compared with no neonatal screening in Libya. METHODS: A decision model was constructed to estimate the cost effectiveness of neonatal screening for PKU, from the perspective of Libyan society. Healthcare resource use and other input parameters were based on expert opinion. RESULTS: The expected discounted cost to Libyan society of screening over 15 years and managing ∼374 patients with detected PKU over their lifetime was estimated to be $US213.6 (95% CI 211.9, 214.3) million (year 2007-8 values). The current expected discounted cost of managing these same PKU patients over their lifetime as a result of not screening was estimated to be $US321.2 (95% CI 318.0, 322.7) million. Hence, screening would save Libyan society $US107.6 (95% CI 105.5, 109.1) million over the lifetime of PKU patients and lead to an additional 6947 life-years (95% CI 6837, 7056). The expected cost per undiscounted life-year gained was estimated to be -$US15,500 (95% CI -16,600, 1100). There would be a 90% return on investment in the screening programme since society would gain $US1.9 for every $US1 invested. Probabilistic sensitivity analysis demonstrated that the screening programme has a 0.95 probability of being cost effective even at a willingness-to-pay threshold of $US4000 per life-year gained. CONCLUSIONS: Within the model's limitations, neonatal screening for PKU appears to offer Libyan society a strategy that is cost effective compared with no neonatal screening.

Phenylketonuria.

Phenylketonuria is the most prevalent disorder caused by an inborn error in aminoacid metabolism. It results from mutations in the phenylalanine hydroxylase gene. Phenotypes can vary from a very mild increase in blood phenylalanine concentrations to a severe classic phenotype with pronounced hyperphenylalaninaemia, which, if untreated, results in profound and irreversible mental disability. Neonatal screening programmes identify individuals with phenylketonuria. The initiation of a phenylalanine-restricted diet very soon after birth prevents most of the neuropsychological complications. However, the diet is difficult to maintain and compliance is often poor, especially in adolescents, young adults, and pregnant women. Tetrahydrobiopterin stimulates phenylalanine hydroxylase activity in about 20% of patients, and in those patients serves as a useful adjunct to the phenylalanine-restricted diet because it increases phenylalanine tolerance and allows some dietary freedom. Possible future treatments include enzyme substitution with phenylalanine ammonia lyase, which degrades phenylalanine, and gene therapy to restore phenylalanine hydroxylase activity.

[Diagnosis, treatment and long-term following up of 223 patients with hyperphenylalaninemia detected by neonatal screening programs].

OBJECTIVE: To investigate the incidence of hyperphenylalaninemia (HPA) caused by different etiologic factors in China and the relationship between the phenylalanine and mental development of patients with HPAs who were diagnosed by neonatal screening and early treated. METHODS: Two hundred and twenty-three patients with HPA detected by neonatal screening programs were refered to us at the age of (41 +/- 27) days after birth. The differential diagnosis was performed by BH(4) (20 mg/kg) loading test, urinary pterin analysis and dihydropteridine reductase (DHPR) activity determination respectively. The control of phenylalanine (Phe) metabolism, growth and mental development were evaluated in all treated patients. Related gene mutation analysis was performed in some patients RESULTS: One hundred and twenty-nine of 223 patients (57.8%) were diagnosed as phenylalanine hydroxylase deficiency (PAHD), 64 patients (28.7%) as BH(4) responsive PAHD, 30 patients (13.5%) as 6-pyruvoyl tetrahydropterin synthase deficiency (PTSD). One hundred and forty-nine patients were followed at age of 4 m - 2 y in our clinic. The 136 of 149 patients were treated according to different etiology at the age of 1.6 m (0.5 - 3.5 m) after birth. Thirteen patients were followed up without the need for treatment. All patients had normal growth development. One hundred and eight (79.4%) of 136 treated patients had normal mental development. The negative correlation (r = -0.439, P < 0.01) between IQ and average Phe levels were observed in 58 patients. Twenty-eight patients were able to go to primary school or even university. Nine kinds of PTS gene mutations were found in 9 cases with PTSD, among which 286G-->A and 259C-->T were most commonly seen, accounting for 45%. Seven kinds of PAH gene mutations were found in 13 cases with BH(4) responsive PAHD with the R241C (43.8%) mutation being the most frequent one. CONCLUSION: The differential diagnosis should be quickly made in all HPA patients detected by neonatal screening. Near 80% patients early treated had normal mental development. The good control of blood Phe level is a key factor for mental development.

Low therapeutic threshold for hepatocyte replacement in murine phenylketonuria.

Phenylalanine homeostasis in mammals is primarily controlled by liver phenylalanine hydroxylase (PAH) activity. Inherited PAH deficiency (phenylketonuria or PKU) leads to hyperphenylalaninemia in both mice and humans. A low level of residual liver PAH activity ensures near-normal dietary protein tolerance with normal serum phenylalanine level, but the precise threshold for normal phenylalanine clearance is unknown. We employed hepatocyte transplantation under selective growth conditions to investigate the minimal number of PAH-expressing hepatocytes necessary to prevent hyperphenylalaninemia in mice. Serum phenylalanine levels remained normal in mice exhibiting nearly complete liver repopulation with PAH-deficient hepatocytes (<5% residual wild-type liver PAH activity). Conversely, transplantation of PAH-positive hepatocytes into PAH-deficient Pah(enu2) mice, a model of human PKU, yielded a significant decrease in serum phenylalanine (<700 muM) when liver repopulation exceeded approximately 5%. These data suggest that restoration of phenylalanine homeostasis requires PAH activity in only a minority of hepatocytes.