A novel large deletion (exons 12, 13) and a missense mutation (p.G46R) in the PAH in a Japanese patient with phenylketonuria.

Background: Phenylketonuria (PKU) is caused by a defect in phenylalanine hydroxylase (PAH). More than 500 mutations have been reported for the gene encoding PAH. However, approximately 1%-5% of these include large deletions and large duplications that cannot be detected by conventional methods.

Methods: In this report we tried to fully characterize a PAH-deficient patient. The patient was a 2-year-old Japanese boy who was diagnosed with classical PKU at the time of neonatal screening, which was confirmed by the tetrahydrobiopterin-loading test. PCR-related direct sequencing and multiplex ligation-dependent probe amplification (MLPA) were used to analyze of the PAH of the patient.

Results: Using PCR-related direct sequencing method, we could detect only a heterozygous novel missense mutation: p.136G>C (p.G46R). A second mutation was detected by MLPA. The patient was heterozygous for a novel large deletion of exons 12 and 13: c.1200-?_1359+?del (EX12_13del). For genetic counseling, an accurate genetic diagnosis is often necessary.

Conclusions: Through a combination of MLPA and conventional methods, the success rate of PAH mutation identification can be close to 100%.