[Genotype and phenotype correlation of phenylalanine hydroxylase deficiency among patients from Henan]

To delineate the mutation spectrum of phenylalanine hydroxylase (PAH) gene among patients affected with phenylalanine hydroxylase deficiency (PAHD) in Henan Province of China, and to explore the correlation between the genotype and the phenotype.

A total of 155 affected children were recruited. Potential mutation of the PAH gene were analyzed by direct sequencing. The genotype-phenotype correlation was analyzed by matching the expected and observed phenotypes.

Over 72 mutations and 108 genotypes have been identified. There were 7 homozygous mutations, including 1 case with EX6-96A>G/EX6-96A>G, 1 with R241C/R241C, 1 with R413P/R413P, and 4 with R243Q/R243Q. Among these, 6 patients have presented classic PKU phenotypes, except for a R241C/R241C genotype which has led to mild PKU. In 104 patients carrying compound PAH mutations, 52 were classic, 34 were mild and 39 had mild HPA. Patients who were heterozygous for EX6-96A>G/R241C, R243Q/A434D, EX6-96A>G/R413P and EX6-96A>G/ R241C were found with both the classic PKU and mild PKU phenotypes. Common mutations associated with mild HPA have included R53H, R243Q, V399V and H107R. The common mutations associated with mild PKU included R243Q, R241C, EX6-96A>G, and IVS4-1G>A. The prevalent mutations in classic PKU were R243Q, EX6-96A>G and V399V. The consistency between prediction of the biochemical genotype and observed phenotype was 77.78%, especially in classic PKU, the consistency was up to 82.14%. Significant correlations were disclosed between pretreatment levels of phenylalanine and AV sum (r=-0.6729, P < 0.01).

The mutation spectrum of PAH gene in Henan seems to differ from that of other regions. Independent assortment of mutant alleles may result in a complex genotype-phenotype correlation, but the genotypes of PAHD patients have correlated with the phenotype.