Inborn error of phenylalanine metabolism. Results in
severe irreversible mental retardation at infancy.
1:10,000 to 12,000 live births in North America;
considerable geographic variability.
Deficiency of the liver enzyme phenylalanine
hydroxylase, which converts phenylalanine to tyrosine; it leads to
accumulation of phenylalanine and abnormal metabolites thereof.
Neonatal screening programs for phenylketonuria (PKU)
are established in many countries (Guthrie test). Elevated plasma levels of
phenylalanine are seen in affected infants after protein feeding.
Affected infants are normal at birth. Untreated
children develop severe mental retardation with movement disorders. They
typically have pale, dry skin and blue eyes. Severe vomiting, mimicking
infantile pyloric stenosis, may be the presenting feature. Typical mousy
pungent odor caused by the excretion of phenylacetic acid. Perirectal
eczema-like or scleroderma-like skin rash. Treatment consists of a diet low
Ensure patient is receiving
There should be no difficulties with
anesthetic management of children who are receiving appropriate dietary
There are no specific implications.
Tetrahydrobiopterin (BH4) Deficiency: Of
children with phenylketonuria, 1 to 2% have a defect in the gene coding
for that cofactor of phenylalanine hydroxylase instead of a deficiency in
the enzyme itself. BH4 deficiency also causes decreased synthesis of
l-dopa, 5 hydroxytryptophan, and nitric oxide (NO). Without treatment,
the most severe form leads to microcephaly, developmental delay, and
progressive neurological deterioration with parkinsonian symptoms. Treatment
includes the daily administration of l-dopa (up to 10 to 12 mg/kg/d)
and 5-hydroxytryptophan (up to 8-10 mg/kg/d).
Dal D, Celiker V: Anesthetic management of a strabismus patient with phenylketonuria Paediatr Anaesth
Rezvani I: Defects in metabolism of amino acids, in Behrman RE, Kliegman
RM, Arvin AM (eds): Nelson Textbook of Pediatrics. 15th ed. Philadelphia, WB
Saunders, 329-333, 1995.