phenylketonuria_flashcards
What is phenylketonuria (PKU)?
An autosomal recessive condition caused by a disorder of phenylalanine metabolism.
What causes PKU?
Usually due to a defect in phenylalanine hydroxylase.
What enzyme is usually defective in PKU?
Phenylalanine hydroxylase.
What is the role of phenylalanine hydroxylase?
Converts phenylalanine to tyrosine.
What can high levels of phenylalanine lead to?
Learning difficulties and seizures.
Where is the gene for phenylalanine hydroxylase located?
On chromosome 12.
What is the incidence of PKU?
Around 1 in 10,000 live births.
What are the features of PKU?
Developmental delay, fair hair and blue eyes, learning difficulties, seizures, eczema, ‘musty’ odour to urine and sweat.
When does PKU usually present?
By 6 months of age.
What is the classic appearance of a child with PKU?
Fair hair and blue eyes.
What test is used for diagnosing PKU?
Guthrie test (‘heel-prick’ test) done at 5-9 days of life.
What biochemical markers indicate PKU?
Hyperphenylalaninaemia, phenylpyruvic acid in urine.
What is the management strategy for PKU?
There is poor evidence to suggest strict diet prevents learning disabilities, but dietary restrictions are important during pregnancy.
Why are dietary restrictions important during pregnancy for women with PKU?
Genetically normal fetuses may be affected by high maternal phenylalanine levels.
