This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Mild phenylketonuria is a rare form of phenylketouria (PKU variant), an inborn error of amino acid metabolism, characterized by symptoms of PKU of mild to moderate severity. Patients with blood phenylalanine concentrations of 600-1,200 micromol/L are considered to have mild PKU. Clinical signs include reduced cognitive function and behavioral and developmental disorders. It is caused by certain mutations in the PAH gene which result in slightly higher activity of the phenylalanine hydroxylase compared with the classic phenylketonuria where there is a complete or near-complete deficiency of phenylalanine hydroxylase activity. Inheritance is autosomal recessive. Treatment is with a diet low in phenylalanine (patients can have up to 400-600 mg/day of phenylalanine).
For more information, visit GARD.