Variations in genotype-phenotype correlations in phenylalanine hydroxylase deficiency in Chinese Han population.
BACKGROUND
The value of genotyping to predict variant phenotypes in patients with phenylalanine hydroxylase (Pah) deficiency is a matter of debate. However, there exists no comprehensive population relationship study focused on the Han Chinese.


METHODS
We analyzed genotype-phenotype correlation for 186 different genotypes in 338 unrelated Chinese patients harboring 109 different Pah mutations. Two systems were used in this process. The first was a phenotype prediction system based on arbitrary values (AV) attributed to each mutation. The second was a pair-wise correlation analysis. The observed phenotype for AV analysis was the corresponding metabolic phenotype stratified according to the pretreatment phenylalanine (Phe) value.


RESULTS
We found that the observed phenotype matched the predicted phenotype in 54.41% of 272 patients for whom AV information was available; the highest degree of concordance (61.83%) was found in patients with null/null genotypes, whereas the lowest "concordance rate" (32.69%) was observed for patients with expected mild-PKU phenotype. There are repeated inconsistencies for such mutations as R241C, R243Q, R261Q, V388M, V399V, R408Q, A434D and EX6-96A>G which are associated with variable phenotypes in patients with identical genotype. Significant correlations were disclosed between pretreatment Phe values and predicted residual activity (r=-0.45643, P<0.0001) or AV sum (r=-0.59523, P<0.0001).


CONCLUSIONS
Our study supports the notion that the Pah mutation genotype is the main determinant of metabolic phenotype in most patients in a particular population, and provided novel insights into the values that underpin the subsequent treatment and the prognosis of PKU in Chinese.
Department of Neonatal Medicine, Xin-Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, China.
Tianwen
T
Zhu
Jun
J
Ye
Lianshu
L
Han
Wenjuan
W
Qiu
Huiwen
H
Zhang
Lili
L
Liang
Xuefan
X
Gu
D000483:Alleles; D044466:Asian People / Q000235:genetics; D002681:China; D005091:Exons; D056726:Genetic Association Studies; D056426:Genetic Loci; D023281:Genomics; D005838:Genotype; D006801:Humans; D009154:Mutation; D010641:Phenotype; D010649:Phenylalanine / Q000097:blood / Q000627:therapeutic use; D010651:Phenylalanine Hydroxylase / Q000097:blood / Q000235:genetics; D010661:Phenylketonurias / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology; D011379:Prognosis
D010649:Phenylalanine; D010651:Phenylalanine Hydroxylase
AV; Chinese Han population; Complex phenotypes; MHP; PAHD; PKU; PRA; Pah; Phe; Phenotype–genotype correlation; arbitrary value; mild hyperphenylalaninemia; phenylalanine; phenylalanine hydroxylase; phenylalanine hydroxylase deficiency; phenylketonuria; predicted residual PAH activity