Molecular epidemiology, genotype-phenotype correlation and BH4 responsiveness in Spanish patients with phenylketonuria

• Published in: Journal of human genetics 2016-08, Vol.61 (8), p.731-744
• Main Authors: Aldámiz-Echevarría, Luis, Llarena, Marta, Bueno, María A, Dalmau, Jaime, Vitoria, Isidro, Fernández-Marmiesse, Ana, Andrade, Fernando, Blasco, Javier, Alcalde, Carlos, Gil, David, García, María C, González-Lamuño, Domingo, Ruiz, Mónica, Ruiz, María A, Peña-Quintana, Luis, González, David, Sánchez-Valverde, Felix, Desviat, Lourdes R, Pérez, Belen, Couce, María L
• Format: Article
• Language: English
• Subjects: Alleles; Enzyme Replacement Therapy; Gene Frequency; Genetic Association Studies; Genetic Heterogeneity; Genotype; Humans; Molecular Epidemiology; Mutation; Phenotype; Phenylalanine Hydroxylase - genetics; Phenylalanine Hydroxylase - metabolism; Phenylketonurias - diagnosis; Phenylketonurias - epidemiology; Phenylketonurias - genetics; Phenylketonurias - therapy; Spain - epidemiology
• ISSN: 1434-5161; 1435-232X
• DOI: 10.1038/jhg.2016.38

Phenylketonuria (PKU), the most common inborn error of amino acid metabolism, is caused by mutations in the phenylalanine-4-hydroxylase (PAH) gene. This study aimed to assess the genotype-phenotype correlation in the PKU Spanish population and the usefulness in establishing genotype-based predictions of BH4 responsiveness in our population. It involved the molecular characterization of 411 Spanish PKU patients: mild hyperphenylalaninemia non-treated (mild HPA-NT) (34%), mild HPA (8.8%), mild-moderate (20.7%) and classic (36.5%) PKU. BH4 responsiveness was evaluated using a 6R-BH4 loading test. We assessed genotype-phenotype associations and genotype-BH4 responsiveness in our population according to literature and classification of the mutations. The mutational spectrum analysis showed 116 distinct mutations, most missense (70.7%) and located in the catalytic domain (62.9%). The most prevalent mutations were c.1066-11G>A (9.7%), p.Val388Met (6.6%) and p.Arg261Gln (6.3%). Three novel mutations (c.61-13del9, p.Ile283Val and p.Gly148Val) were reported. Although good genotype-phenotype correlation was observed, there was no exact correlation for some genotypes. Among the patients monitored for the 6R-BH4 loading test: 102 were responders (87, carried either one or two BH4-responsive alleles) and 194 non-responders (50, had two non-responsive mutations). More discrepancies were observed in non-responders. Our data reveal a great genetic heterogeneity in our population. Genotype is quite a good predictor of phenotype and BH4 responsiveness, which is relevant for patient management, treatment and follow-up.