Metabolics

Question 1

Which cofactor defect is associated with phenylketonuria?

Answer 1

Tetrahydrobiopterin (BH4) is an essential cofactor for phenylalanine hydroxylase. Defects in BH4 metabolism can account for around 2% of patients presenting with elevated phenylalanine levels. Presentation is similar to PKU, and diagnosis can be made by measuring elevated levels of biopterin or neopterin in the blood, urine or CSF. Treatment includes diet low in phenylalanine and BH4 supplementation.