Review Question - QID 106529

This child is suffering from Phenylketonuria (PKU), which presents with the classic symptoms of musty odor and eczema.

Classical PKU results from a deficiency in the enzyme phenylalanine hydroxylase. Screening for PKU is commonly performed as part of the newborn screen. Once identified, patients with PKU are instructed to consume a diet low in phenylalanine. Foods high in phenylalanine include meat, fish, eggs and legumes. If this diet is not followed, it can lead to progressive neurologic deterioration. The musty odor is secondary to phenyl acetate accumulation in the urine and sweat.

Koch emphasizes the importance of newborn screening for PKU. He notes that screening has largely eliminated the development of mental retardation from this disorder.

Ney et al. review the current recommendation for pharmacologic and nutritional management of PKU. They endorse the use of glycomacropeptide to improve bone health and the use of tetrahydrobiopterin to improve tolerance to dietary phenylalanine.

Illustration A is a diagram displaying the metabolic pathway of phenylalanine. PKU is produced from a deficiency in the enzyme phenylalanine hydroxylase.

Incorrect Answers:
Answer 1, 5: Patients with maple syrup urine disease suffer from the accumulation of branched chain amino acids.
Answer 3, 4: The build up of these compounds is the result of a deficiency within the urea cycle, resulting in hyperammonemia.