Identification of Mutations Causing 6-Pyruvoyl- Tetrahydrobiopterin Synthase Deficiency in Polish Patients With Variant Hyperphenylalaninemia.

Background: 6-Pyruvoyl-tetrahydrobiopterin synthase (PTPS) is required for biosynthesis of tetrahydrobiopterin, the cofactor of various enzymes including the hepatic phenylalanine hydroxylase. Mutations in the PTS gene result in a variant type of hyperphenylalaninemia, requiring cofactor replacement therapy for treatment. Methods and Results: Four Polish patients with PTPS deficiency were screened for mutations in the PTS gene. Three novel mutations E35G, N36K, and F100V were identified. In one patient, a known mutation D136V was identified in both PTS alleles. Conclusions: Mutation D136V present in both alleles was proposed to be connected with a mild form of PTPS deficiency. The other three mutations were found in heterozygous patients with a central type of PTPS deficiency. D136V mutation is a common mutation in the Polish population.

Should newborn mutation scanning for hyperphenylalaninaemia and galactosaemia be implemented? A Polish experience.

OBJECTIVE: To elucidate whether screening for mutations causing hyperphenylalaninaemia (HPA) and classic galactosaemia could provide important, additional information on a clinical phenotype. METHOD: Genotypes that cause disease at the phenylalanine hydroxylase (PAH) gene and galactose-1-phosphate uridyltransferase (GALT) gene in a group of 101 hyperphenylalaninaemic and 77 patients with classic galactosaemia were established. The PAH and GALT mutations were identified in genomic DNA extracted from whole blood leucocytes using single stranded conformational analysis and direct fluorescent sequencing of polymerase chain reaction (PCR) products. RESULTS: Mild HPA and mild phenylketonurea (PKU) were caused by divergent genotypes. In the studied group a total of 26 different mild and intermediate PAH mutations were identified, most of them being rare ones. Classic galactosaemia was caused by two frequent mutations, accounting for 82% of all mutated alleles. CONCLUSIONS: Identification of mild or intermediate mutations causing HPA could provide fast and reliable information about future clinical outcome of a newborn infant. Molecular diagnosis of HPA should be preceded by biochemical analysis and implemented to differentiate mild forms of HPA and cases of ambiguous classification. Because of multiple rare mutations scattered on all exons, scanning of the entire PAH coding sequence could be useful and cost beneficial. Routine genotyping is not proposed in classic phenylketonuria and classic galactosaemia, as it provides limited additional, prospective information on the clinical phenotype.

Mutations in exon 3 of the PAH gene causing mild hyperphenylalaninemia.

Phenylketonuria (PKU), an autosomal recessive disorder caused by a deficiency of hepatic phenylalanine hydroxylase (PAH), is clinically very heterogeneous. On molecular level more than 350 mutations in the PAH gene are known to date, which in different genotype combinations could account for biochemical and clinical variability. Mutations located in exon 3 coding for a part of the regulatory domain of the PAH enzyme cause classical PKU, mild PKU, and mild hyperphenylalaninemia (MHP). We describe the phenotypic effects of seven mutations in exon 3 of the PAH gene (R68G, R68S, R71H, S87R, P89S, I95F, and A104D). We propose that mutations located between amino acid positions 71 through 94 cause MHP.

[Maternal PKU syndrome as an obstetric problem: literature review and own clinical experience]. / Zespól fenyloketonurii matczynej jako problem polozniczy--przedstawienie wspólczesnych pogladów i wlasnych doswiadczen klinicznych.

Maternal phenylketonuria (M-PKU) is a syndrome of embryo- and fetopathy observed in the offsprings of mothers with increased blood level of phenylalanine. These women fall into two groups: phenylketonuria (PKU) and mild hyperphenylalaninemia (MHP). The Phe--level safe for the fetus is 4-6 mg%. Typical for M-PKU syndrome is: microcephalia, mental retardation, intrauterine growth retardation, congenital heart diseases and other anomalies like esophageal atresia, meningocoele, Pierre-Robin syndrome, cataract. The only way to prevent this syndrome is Phe--restricted diet that should be initiated before conception. We reviewed updated literature on the pathogenesis of this syndrome, clinic, possibility of prophylaxis and treatment. We present also 5 pregnancies of 3 patients with PKU, treated in National Research Institute of Mother and Child in Warsaw. On that ground we propose the scheme of prevention of maternal PKU syndrome.