The proportion of tetrahydrobiopterin deficiency and PAH gene deficiency variants among cases with hyperphenyalaninemia in Western Iran.

BACKGROUND: Defects either in phenylalanine hydroxylase (PheOH) or in the production and recycling of its cofactor (tetrahydrobiopterin [BH4]) are the causes of primary hyperphenylalaninemia (HPA). The aim of our study was to investigate the current status of different variants of HPA Kurdish patients in Kermanshah province, Iran. MATERIALS AND METHODS: From 33 cases enrolled in our study, 32 were identified as HPA patients. Reassessing of pre‑treatment phenylalanine concentrations and the analysis of urinary pterins was done by high‑performance liquid chromatography method. RESULTS: A total of 30 patients showed PAH deficiency and two patients were diagnosed with BH4 deficiency (BH4/ HPA ratio = 6.25%). Both of these two BH4‑deficient patients were assigned to severe variant of dihydropteridine reductase (DHPR) deficiency. More than 75% of patients with PAH deficiency classified as classic phenylketonuria (PKU) according their levels of pre‑treatment phenylalanine concentrations. CONCLUSION: Based on the performed study, we think that the frequency of milder forms of PKU is higher than those was estimated before and/or our findings here. Furthermore, the frequency of DHPR deficiency seems to be relatively high in our province. Since the clinical symptoms of DHPR deficiency are confusingly similar to that of classic PKU and its prognosis are much worse than classical PKU and cannot be solely treated with the PKU regime, our pilot study support that it is crucial to set up screening for BH4 deficiency, along with PAH deficiency, among all HPA patients diagnosed with HPA.

Sapropterina no tratamento da hiperfenilalaninemia com deficiência de BH4 / Sapropterin in the treatment of hyperphenylalaninemia with BH4 deficiency

Fenilcetonúria (FNC) é uma doença genética, autossômica recessiva, causada por mutações no gene localizado no cromossomo 12q22-q24, o qual codifica a enzima hepática fenilalanina-hidroxilase (FAH). Sua ausência ou deficiência impede a conversão hepática de fenilalanina (FAL), um dos aminoácidos essenciais e mais comuns do organismo, em tirosina, causando acúmulo de FAL no sangue e em outros tecidos. O aumento de fenilalanina no sangue em 98% dos casos é devido a mutações na codificação genética para a enzima fenilalanina-hidroxilase, enquanto 2% são devidos a defeitos no metabolismo da tetrahidrobiopterina (BH4), que é um cofator essencial para a atividade da fenilalanina-hidroxilase. A principal característica da doença não tratada é retardo mental, com piora durante a fase de desenvolvimento do cérebro e que se estabilizaria com a maturação completa deste órgão. O quociente de inteligência (QI) mede a extensão deste retardo e varia de leve a gravemente prejudicado. A HFA não tratada resulta em progressivo retardo mental, com QI < 50. A piora está relacionada aos níveis sanguíneos de FAL. Caso a doença seja diagnosticada logo após o nascimento e o paciente for mantido em dieta restrita em FAL, os sintomas podem ser prevenidos e a criança pode ter desenvolvimento e expectativa de vidas normais. Nesse sentido, o rastreamento no Brasil é realizado pelo teste do pezinho, cuja necessidade consta no Estatuto da Criança e do Adolescente, e está regulamentado pela portaria que estabeleceu o Programa Nacional de Triagem Neonatal para diagnóstico precoce de fenilcetonúria. No Protocolo Clínico e Diretrizes Terapêuticas do Ministério da Saúde para Fenilcetonúria foram incluídos os pacientes com níveis de FAL≥ 10mg/dl (600 µmol/l) em dieta normal 1,14 e todos os que apresentarem níveis de FAL entre 8 e 10 mg/dl persistentes (pelo menos em 3 dosagens consecutivas, semanais, em dieta normal). Dieta restrita em FAL é eficaz em reduzir os níveis sanguíneos de FAL e melhorar o QI e o prognóstico neuropsicológico dos pacientes com HFA. O tratamento deve ser iniciado tão cedo quanto possível, idealmente até o 10º dia de vida. O aleitamento materno deve ser encorajado e associado ao uso de fórmula isenta de FAL. Os níveis de FAL devem ser diminuídos rapidamente. Além da dieta, o tratamento clínico recomendado pelo PCDT do Ministério da Saúde para o controle metabólico dos pacientes é a utilização de fórmulas alimentares especiais. As fórmulas são medicamentos que devem conter as quantidades recomendadas de vitaminas e sais minerais adequadas à faixa etária do paciente. Sapropterina é uma forma sintética oral de BH4 (BH4 supplementation sapropterin dihydrochloride). Há relatos de casos de pessoas com FCN que apresentaram boa resposta após o uso de doses farmacológicas de BH4, com redução dos níveis de FAL. Todos tinham mutação no gene FAH. Pessoas com resposta ao BH4 são identificadas inicialmente por um teste com teste de tolerância a BH4. Resposta positiva é considerada como uma redução de 30% ou mais na concentração de FAL, 24 horas após a administração de BH4. A variação na intensidade da resposta é independente da gravidade da FCN, da dose de BH4 empregada no teste de tolerância, duração do teste e genótipo. Pessoas com mesmo genótipo mostram respostas diferentes. Há poucos resultados de uso de longa duração de BH4 que mostram que pode haver relaxamento da restrição dietética sem efeitos adversos. A maioria dos indivíduos dos estudos apresentava doença moderada ou leve. A Secretaria-Executiva da CONITEC realizou busca na literatura por artigos científicos, com o objetivo de localizar a melhor evidência científica disponível sobre o tema. A CONITEC em sua 14ª reunião ordinária realizada no dia 04 de abril de 2013, recomendou a não incorporação no SUS da sapropterina para o tratamento de hiperfenilalaninemia (HFA) com deficiência em tetrahidrobiopterina (BH4). Considerou-se que os estudos, a maioria de baixa qualidade metodológica, não conseguiram comprovar a superioridade do tratamento, principalmente no que diz respeito à ausência de dados específicos para o subgrupo com deficiência de BH4. Os membros da CONITEC presentes na 15ª reunião do plenário do dia 09/05/2013 deliberaram, por unanimidade, por não recomendar a sapropterina para o tratamento de hiperfenilalaninemia (HFA) com deficiência em tetrahidrobiopterina (BH4). A Portaria nº 34, de 6 de agosto de 2013 - Torna pública a decisão de não incorporar o medicamento sapropterina no tratamento da hiperfenilalaninemia com deficiência de BH4 no Sistema Único de Saúde (SUS).

Triagem neonatal para hiperfenilalaninemia: um estudo de coorte / Newborn screening for hyperphenylalaninemia: a cohort study

Introdução: A Fenilcetonúria Clássica é causada pela deficiência da enzima hepática fenilalaninahidroxilase. Se não diagnosticada e tratada precocemente, causa retardo mental. O objetivo deste estudo foi identificar indivíduos submetidos à triagem neonatal no Rio Grande do Sul entre 1986 e 2003, com teste positivo para hiperfenilalaninemia, estimar a prevalência de hiperfenilalaninemias, verificar níveis de controle e correlacionar os anos de realização do teste, início do tratamento, evolução e quadro clínico. Métodos: Casos de hiperfenilalaninemia foram identificados nos laboratórios e clínicas de tratamento. Foi aplicado questionário, contendo variáveis demográficas e sobre a patologia, o desenvolvimento infantil, a escolaridade, o aconselhamento genético e o rastreamento neonatal. Foram avaliados pacientes entre 6 meses e 16 anos de idade. Na análise estatística, utilizou-se o teste do qui-quadrado e ANOVA para avaliar a associação entre ano do diagnóstico e controle de fenilalanina e regressão logística para avaliar o efeito conjunto de idade do diagnóstico e controle de fenilalanina sobre o atraso no desenvolvimento. Resultados: De 1986 a 2003, 418 crianças apresentaram teste positivo para fenilalanina. Destes, 351 (84,0%) apresentaram resultados normais na segunda amostra, 58 (13,9%) foram considerados portadores de hiperfenilalaninemia e 9 (2,1%) tiveram o seguimento perdido. A cobertura do programa foi de 50%. Sobre o aconselhamento genético, 39 entrevistados (72,2%) responderam não saber, não lembrar ou deram respostas incorretas. Conclusão: Não se observou tendência histórica do diagnóstico ter se tornado mais precoce ou do controle laboratorial ter se tornado melhor. O controle bioquímico da fenilalanina não dependeu da precocidade do diagnóstico e sim, da idade dos pacientes.

Introduction: Classical phenylketonuria is caused by deficiency of the hepatic enzyme phenylalanine hydroxylase. If not diagnosed and treated early, it causes mental retardation. The aim of this study was to identify patients who underwent neonatal screening in Rio Grande do Sul between 1986 and 2003 and tested positive for hyperphenylalaninemia, to estimate the prevalence of hyperphenyl-alaninaemias, to check the levels of control, and to correlate the years of testing, initiation of treatment, evolution and clinical picture. Methods: Cases of hyperphenylalaninemia were identified in laboratories and treatment clinics. A questionnaire was administered containing demographic variables and about the pathology, child development, education, genetic counseling and neonatal screening. We evaluated patients between 6 months and 16 years of age. The statistical analysis used the chi-square test and ANOVA to assess the association between year of diagnosis and control of phenylalanine and logistic regression to assess the combined effect of age at diagnosis and control of phenylalanine on the developmental delay. Results: From 1986 to 2003, 418 children tested positive for phenylalanine. Of these, 351 (84.0%) had normal results in the second sample, 58 (13.9%) were considered with hyperphenylalaninemia, and 9 (2.1%) were lost for follow-up . The coverage of the program was 50%. Concerning genetic counseling, 39 respondents (72.2%) reported not knowing, not remembering or gave incorrect answers. Conclusion: There was no historical trend of diagnosis having become earlier or of laboratory control having improved. The biochemical control of phenylalanine was dependent on patient age rather than on early diagnosis.

Síndrome de fenilquetonuria materna, un nuevo desafío para Chile / Maternal phenylketonuria syndrome, a new challenge for Chile

Phenylquetonuria (PKU) is a hereditary disease, caused by the deficiency or absence of the enzyme phenylalanine hydroxylase, which produces an abnormal conversion of phenylalanine (Phe) to tyrosine. If PKU is not diagnosed and treated during the neonatal period, blood accumulation of Phe causes neurological damage. Chile has a neonatal screening program for PKU and congenital hypothyroidism since 1992; this program has diagnosed 162 PKU patients in Chile, which are being followed-up in INTA, Universidad de Chile. Nowadays, there are 20 PKU patients in adolescence, so we face a new challenge such as maternal PKU syndrome. This syndrome refers to the teratogenic effect of Phe in a pregnant PKU female. The most frequent anomalies are intrauterine growth retardation, microcephaly, global development retardation and congenital heart defects. Their occurrence is directly related to maternal Phe during pregnancy. In order to assure a normal pregnancy and to prevent this syndrome, levels of Phe in blood should be kept between 2 and 6 mgldl prior to conception and throughout pregnancy. Considering this challenge, INTA has proposed a strict protocol of follow-up to improve the compliance to nutritional therapy and prevent maternal PKU syndrome.

La fenilquetonuria (PKU) es una patología hereditaria, producida por la deficiencia o ausencia de la enzima fenilalanina hidroxilasa, lo que impide la metabolización normal de la fenilalanina (FA) a tirosina. La acumulación de fenilalanina en la sangre ocasiona daño neurológico si no es diagnosticada y tratada desde el periodo neonatal. Desde 1992 Chile tiene un programa de pesquisa neonatal de PKU e hipotiroidismo congénito, lo que ha permitido diagnosticar 162 casos con PKU, los que mantienen un seguimiento integral en el INTA, de la Universidad de Chile. Actualmente hay 20 PKU en etapa de adolescencia, por lo que nos enfrentamos a un nuevo desafío, el síndrome de PKU materna. Este síndrome se refiere al efecto teratogénico de la FA en una embarazada con PKU. Las alteraciones más características son el retraso del crecimiento intrauterino, la microcefalia, el retraso global del desarrollo y los defectos cardiacos congénitos. La presencia de estas alteraciones está directamente relacionada con los niveles de FA de la madre durante el embarazo. Para asegurar un embarazo normal y prevenir este síndrome se recomienda la mantención de niveles de FA entre 2 y 6 mg/dl, desde el período preconcepcional y durante todo el embarazo. El INTA considerando este desafío, ha propuesto un protocolo de seguimiento estricto preconcepcional y durante el embarazo con el objetivo de favorecer la adherencia al tratamiento nutricional y prevenir el síndrome de PKU materna.

Tissue-specific activation of mitogen-activated protein kinases for expression of transthyretin by phenylalanine and its metabolite, phenylpyruvic acid

Phenylketonuria is an autosomal recessive disorder caused by a deficiency of phenylalanine hydroxylase. Transthyretin has been implicated as an indicator of nutritional status in phenylketonuria patients. In this study, we report that phenylalanine and its metabolite, phenylpyruvic acid, affect MAPK, changing transthyretin expression in a cell- and tissue-specific manner. Treatment of HepG2 cells with phenylalanine or phenylpyruvic acid decreased transcription of the TTR gene and decreased the transcriptional activity of the TTR promoter site, which was partly mediated through HNF4alpha. Decreased levels of p38 MAPK were detected in the liver of phenylketonuria-affected mice compared with wild-type mice. In contrast, treatment with phenylalanine increased transthyretin expression and induced ERK1/2 activation in PC-12 cells; ERK1/2 activation was also elevated in the brainstem of phenylketonuria-affected mice. These findings may explain between-tissue differences in gene expression, including Ttr gene expression, in the phenylketonuria mouse model.

[Phenylketonuria and its dietary therapy in children]

Phenylketonuria [PKU] is the most common autosomal recessive disease. Hyperphenylalaninemia is caused by deficiency or inactivity of the phenylalanine hydroxylase in liver. In this disorder phenylalanine in not metabolized to tyrosine. Increased levels of blood phenylalanine causes irreversible brain damage. As infants with PKU do not show any clinical signs in the postnatal period, first stage in treatment is an effective screening and diagnosis. Main treatment of PKU is diet therapy, which should be initiated before the third week of life and monitored by a team formed of a pediatrician, an experienced dietitian, a psychologist, a social worker and a nurse. Phenylalanine-restricted diet should provide enough protein-energy and other nutrients for an optimal growth and brain development and include tyrosine supplement to preserve the phenylalanine plasma concentration in a range of 2 to 6 mg/dl. The exact amount should be prescribed based on age, specific genotype, growth rate and individual need for energy. Successful management of PKU patients should be monitored by growth rate. Duration of diet therapy is controversial; continuing phenylalanine-restricted diet beyond adolescence is recommended

Evolución clínica de niños con niveles plasmáticos de fenilalanina entre 2.1 y 6.0 mg/dl en el período neonatal / Clinical evolution of children with phenylalanine plasma levels between 2.1 and 6.0 mg/dl during the neonatal period

Introducción: La Academia Americana de Pediatría (AAP) ha clasificado la Fenilquetonuria (PKU) e Hiperfenilalaninemia (HFA) según la tolerancia de la ingesta de fenilalanina (FA) en: PKU clásica: 20 mg FA/kg/día, PKU moderada: 21 y 25 mg FA/kg/día y PKU leve: 25 y 50 mg FA/kg/día, e HFA benigna con dieta normal, manteniendo un nivel plasmático de FA entre 2,0 y 10,0 mg/dl. Objetivo: Evaluar la evolución clínica de 67 niños con valores de FA plasmática entre 2.1 y 6.0 mg/dL en el período neonatal. Resultados: Del total, 29 niños tenía entre 0 y 2 años, 23 entre 2 y 4 años y 15 niños eran mayores de 4 años de edad. El estado nutricional de 45 niños era normal, 14 niños estaban con sobrepeso u obesidad, y 8 casos tenían riesgo nutricional. Se determinó que 4 niños tenían una ingesta menor de 20 mg FA/kg/día, dos niños entre 21 y 25 mg FA/kg/día, 15 casos entre los 26 a 50 mg FA/kg/día y 46 niños estaban con dieta normal. Conclusión: Los recién nacidos con niveles de FA entre 2.1 y 6.0 mg/dl durante el período neonatal, tienen una evolución clínica y nutricional diferente, que puede ir desde una PKU clásica a una HFA benigna, por lo cual se recomienda mantener un control frecuente de FA sanguínea y una vigilancia nutricional, con un mínimo de 2 años de seguimiento.

Introduction: The American Academy of Pediatric (AAP) has classified Phenylketonuria (PKU) and Hyperphenylalaninaemias (HPhe) according to tolerance of phenylalanine (Phe) intake in: Classic PKU (20 mg Phe/kg/day), moderate PKU (between 21 and 25 mg Phe/kg/day) and mild PKU (between 25 and 50 mg Phe/kg/day), and benign HPhe with normal diet, maintaining blood Phe levels between 2,0 and 10,0 mg/dL. Objective: To evaluate the clinical evolution of 67 children with blood Phe values between 2,1 and 6.0 mg/dl in the neonatal period. Results: Of the total, 29 children were aged between 0 and 2 years, 23 between 2 and 4 years and 15 children were older than 4 years of age. The nutritional state of 45 children was normal, 14 children were overweight or obese, and 8 were at nutritional risk. Four children had Phe intake below 20 mg/kg/day, two children between 21 and 25 mg/kg/day; 15 cases between 26 to 50 mg/kg/day and 46 children were on normal diet. Conclusion: Newborns with blood Phe levels between 2,1 and 6,0 mg/dl in the neonatal period, had a different clinical and nutritional evolution, which could go from the classic PKU to a benign HPhe. Thus, it is recommended to keep a frequent control of plasmatic Phe levels and nutritional monitoring for a minimum of 2 years of follow up.

Dietoterapia en errores innatos del metabolismo / Nutritional treatment of inborn errors of metabolism

Dependiendo del defecto enzimático, algunos errores innatos del metabolismo (EIM) responden satisfactoriamente a la manipulación de la dieta. Según la alteración metabólica, se han identificado siete formas de tratamiento nutricional, las que permiten reestablecer el balance metabólico. Una de ellas es a través de la reducción del sustrato acumulado causado por la deficiencia primaria de una enzima o por la inhibición secundaria de una de ellas. Un ejemplo ampliamente descrito en la literatura es la fenilquetonuria en la que se ha demostrado que gracias al diagnóstico neonatal temprano, seguido de un tratamiento basado en una dieta restringida en fenilalanina revierten su acumulación previniendo con ello el da¤o neurológico que la enfermedad causa al no ser tratada temprana y adecuadamente. Otra forma de tratamiento es la suplementación de una sustancia nutritiva en déficit debido al defecto metabólico, como ocurre en los defectos del ciclo de la urea, en los cuales donde la arginina debe entregarse como fármaco. Algunos EIM con defecto parcial de la enzima tienen la posibilidad de estimular vías alternas para detoxificar o evitar la síntesis de sustancias nocivas a través drogas o megadosis de vitaminas, un ejemplo es la homocistinuria donde la betaína y piridoxina reducen la producción de homocisteína. Otros defectos enzimáticos abren vías metabólicas alternas, las que generan metabolitos tóxicos, el tratamiento en estos casos, consiste en proporcionar cofactores o megadosis de vitaminas para formar complejos no tóxicos que sean excretados por vía urinaria. Es importante se¤alar que el diagnóstico precoz y el seguimiento estricto a largo plazo, permite que un ni¤o con un EIM se desarrolle normalmente.

Hyperphenylalaninemia in the Philippines.

To present patients with hyperphenylalaninemia (HPA) diagnosed by routine newborn screening and to discuss the principles in managing hyperphenylalaninemia, retrospective clinical chart review was conducted. Newborn screening for phenylketonuria (PKU) was performed using the Guthrie Test or Bacterial Inhibition Assay, utilizing dried blood spots on special filter cards. Positive screens were confirmed through plasma amino acid determination, urinary pterins for tetrahydrobiopterin deficiency, enzyme analysis. Once confirmed, the patients were kept on low-phenylalanine diet and regularly monitored for blood phenylalanine levels and developmental profile. A total of 189,720 newborns were screened from 1996--2001. Seventy five screened positive for PKU; 41 returned for retest; 3 were confirmed positive for HPA. This paper presents the first two cases of HPA detected by the Philippine Newborn Screening Program. The management of each case upon diagnosis is discussed. The significance of early detection and treatment of HPA is emphasized.

Report of VNTR with 13 repeats linked to phenylalanine hydroxylase locus in unaffected members of two PKUfamilies

Phenylketonuria [PKU] is one of the most common metabolic inborn diseases caused by mutations in the phenylalanine hydroxylase [PAH] gene. This gene is linked to a variable number of tandem repeats [VNTR] region which is a polymorphic marker that facilitates the implementation of prenatal diagnosis and carrier screening. In this study, VNTR with 13 repeats that has not been reported previously was observed in 2 PKU families from Fars province, south of Iran. This allele showed 4% frequency in normal individuals

Seguimiento de pacientes con hiperfenilalaninemia diagnosticados precozmente / Follow-up of patients with early diagnostic of hyperphenylalaninemia

Se presentan 17 pacientes con hiperfenilalaninemia diagnosticados en el período neonatal (20,3 ñ 12,6 días de vida), cuyas concentraciones iniciales de fenilalanina sérica eran de 16,5 a 46,2 mg por ciento. En todos el tratamiento dietético comenzó al hacer el diagnóstico y han sido seguidos en un policlínico especial del Instituto de Nutrición y Tecnología de los Alimentos de la Universidad de Chile. Se describen la dieta, los suplementos de minerales y vitaminas requeridos, que han permitido, durante el seguimiento, mantener concentraciones de fenilalanina en el suero entre 2 y 6 mg/dl, salvo transgresiones transitorias que han ocurrido en 2 casos. En 82,2 por ciento de los casos el crecimiento y el desarrollo han sido normales. Se subraya la importancia de tomar la primera muestra en tarjet de papel filtro a todos los recién nacidos antes de cumplir 10 días de vida, para hecer oportunamente el diagnóstico. Los programas se seguimiento integral facilitan el manejo y el desarrollo físico y mental normales de estos niños

Newborn mass screening and molecular genetics of phenylketonuria in east Asia.

Phenylketonuria (PKU) is an autosomal recessive disorder caused by a deficiency of hepatic phenylalanine hydroxylase (PAH), and is performed with newborn mass screening. PKU causes irreversible mental retardation that can be prevented by a strict low-phenylalanine diet. More than 100 different mutations have been identified world wide and it has been revealed that PKU is a highly heterogeneous disorder. Here, we describe the progress of the molecular genetics of PKU in East Asia. Approximately 60% of all PKU alleles in East Asians have been characterized with 10 PKU mutations. Two major PKU mutations, R413P and IVS4nt-1, may have originated in different populations, spreading in prehistoric times through the Asian continent due to the founder effect, genetic drift, and bottleneck effect. We found different mutations in Caucasians and East Asians, thus PKU mutations have occurred after ethnic divergence between Caucasians and East Asians. Furthermore, PKU genotype and in vitro PAH activity in expression analysis correlates to the clinical and biochemical phenotypes in East Asians. The molecular defects at the PAH gene regulate the in vivo PAH activities and clinical manifestations.