non-PKU hyperphenylalaninemia
an autosomal recessive condition caused by mutation in the PAH (locus: 12q24.1), which encodes phenylalanine hydroxylase; the resulting enzyme defect does not abolish enzyme activity; enough activity remains to keep plasma phenylalanine concentrations below 1mM without dietary restriction, and the clinical phenotype is normal.
Medical dictionary.
2011.