Abstract
Neonatal screening for phenylketonuria (PKU, OMIM: 261600) was introduced at the end of the 1960s. We developed a rapid and simple molecular test for the most frequent phenylalanine hydroxylase (PAH, Gene ID: 5053) mutations. Using this method to detect the 18 most frequent mutations, it is possible to achieve a 75% detection rate in Italian population. The variants selected also reach a high detection rate in other populations, for example, 70% in southern Germany, 68% in western Germany, 76% in Denmark, 68% in Sweden, 63% in Poland, and 60% in Bulgaria. We successfully applied this confirmation test in neonatal screening for hyperphenylalaninemias using dried blood spots and obtained the genotype in approximately 48 h. The method was found to be suitable as second tier test in neonatal screening for hyperphenylalaninemias in neonates with a positive screening test. This test can also be useful for carrier screening because it can bypass the entire coding sequence and intron–exon boundaries sequencing, thereby overcoming the questions that this approach implies, such as new variant interpretations.
Highlights
Hyperphenylalaninemias are a group of inherited diseases characterized by an increase of plasma phenylalanine at birth, diagnosed with metabolic newborn screening (NBS) in the first weeks of life
In approximately 98% of cases, the disease is due to mutations in the phenylalanine hydroxylase (PAH) gene (OMIM: 261600); in the remaining 2%, the defect lies in the biopterin metabolism genes (OMIM: 261630, 233910, 261640) [1]
We developed a method to analyze a number of known mutations, similar to the first-level mutation test that is used for the diagnostic purpose and for the carrier screening of cystic fibrosis [10]
Summary
Hyperphenylalaninemias are a group of inherited diseases characterized by an increase of plasma phenylalanine at birth, diagnosed with metabolic newborn screening (NBS) in the first weeks of life. To distinguish the two conditions beyond NBS, it is crucial to perform additional laboratory tests enabling differentiation of PAH defects from biopterin metabolism defects so that a proper treatment, which differs for the two groups of diseases, could be established as soon as possible. For this purpose, genotyping of hyperphenylalaninemic patients can be helpful. Mutation analysis in the PAH gene can help to identify a subgroup of patients who are responsive to tetrahydrobiopterin treatment [4,6] This analysis is indispensable for genetic counseling and for prenatal diagnosis [7,8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
