“Phenylketonuria (PKU) is a common metabolic disorder among Chinese, with a prevalence of about 1 in 16,500 births. This frequency is very similar to that among Caucasians…An Arg111-to-Ter111 mutation has been identified in exon 3 of the PAH gene in a Chinese PKU patient. The mutation is in linkage disequilibrium with the mutant haplotype 4 alleles which are the most prevalent haplotype among the Orientals. The mutation accounts for about 10% of the Chinese PKU alleles and is absent from the Caucasians, demonstrating that independent mutational events have occurred in the PAH locus after racial divergence.”
“Following the introduction 30 years ago of neonatal screening and early dietary treatment for phenylketonuria there has been a dramatic decrease in the severity of neurological dysfunction associated with this disorder. However, there is evidence that subtle neurological impairment remains common in early treated subjects and in the last 3 years there have been a number of reports of overt neurological impairment with white matter abnormalities on MRI...These data are consistent with studies in animals showing that hyperphenylalaninaemia increases myelin turnover in a dose dependent manner. It is suggested that the effects of phenylalanine on myelin pose a lifelong hazard to the nervous system.”
If undiagnosed and untreated, phenylketonuria can result in impaired postnatal cognitive development resulting from a neurotoxic effect of hyperphenylalaninemia.