Inborn Metabolic Diseases

pp 221-232


  • John H. WalterAffiliated withWillink Biochemical Genetics Unit, Royal Manchester Children’s Hospital
  • , Philip J. LeeAffiliated withCharles Dent Metabolic Unit, National Hospital for Neurology & Neurosurgery
  • , Peter BurgardAffiliated withDepartment of General Pediatrics, Universitäts-Kinderklinik

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Mutations within the gene for the hepatic enzyme phenylalanine hydroxylase (PAH) and those involving enzymes of pterin metabolism are associated with hyperphenylalaninaemia (HPA). Phenylketonuria (PKU) is caused by a severe deficiency in PAH activity and untreated leads to permanent central nervous system damage. Dietary restriction of phenylalanine (PHE) along with aminoacid, vitamin and mineral supplements, started in the first weeks of life and continued through childhood, is an effective treatment and allows for normal cognitive development. Continued dietary treatment into adulthood with PKU is generally recommended but, as yet, there is insufficient data to know whether this is necessary. Less severe forms of PAH deficiency may or may not require treatment depending on the degree of HPA. High blood levels in mothers with PKU leads to fetal damage. This can be prevented by reducing maternal blood PHE throughout the pregnancy with dietary treatment. Disorders of pterin metabolism lead to both HPA and disturbances in central nervous system amines. Generally they require treatment with oral tetrahydrobiopterin and neurotransmitters.