PKU
A treatable genetic metabolic disorder. Phenylketonuria (PKU) is caused by deficiency of phenylalanine hydroxylase (PAH), which converts phenylalanine to tyrosine. Without treatment, phenylalanine accumulates and damages the brain. Early detection via newborn screening and dietary management prevents intellectual disability.
Understanding PKU
Enzyme Deficiency
PAH converts phenylalanine to tyrosine. In PKU, this enzyme is deficient or absent.
Phe Accumulation
Phenylalanine builds up in blood and brain. Toxic at high levels.
Brain Damage
Excess Phe interferes with brain development. Causes intellectual disability if untreated.
Tyrosine Deficiency
Can't make tyrosine from phenylalanine. Tyrosine becomes essential. Needed for dopamine.
Autosomal Recessive
Need two copies of mutant gene. Parents are carriers. 25% chance per pregnancy.
Newborn Screening
Detected via heel prick test. Universal screening. Early detection critical.
PKU Treatment
Low-Phe Diet
Restrict protein intake. Special medical formulas. Lifelong management.
Medical Foods
Phe-free amino acid formulas. Low-protein specialty foods.
BH4 (Kuvan)
Some patients respond to BH4 cofactor supplementation. Increases enzyme activity.
Tyrosine Supplement
May need tyrosine since can't make from Phe. For neurotransmitters.
Pegvaliase (Palynziq)
Enzyme substitution therapy. Injectable. Breaks down Phe differently.
Regular Monitoring
Blood Phe levels checked regularly. Target levels vary by age.
Broader Relevance
BH4 Pathway
BH4 also needed for neurotransmitter synthesis. Some people have partial BH4 issues without PKU.
Aspartame Concern
Aspartame contains phenylalanine. PKU patients must avoid. Warning on labels.