II. Epidemiology
- Incidence: 1:15000
III. Pathophysiology
- Autosomal-recessive disorder
-
Phenylalanine hydroxylase gene mutation
- Enzyme converts Phenylalanine to Tyrosine
- Phenylalanine concentrations rise with mutation
- Phenylalanine threshold for adverse effects >20 mg/dl
IV. Symptoms
- Irritability
V. Signs: Complications on unrestricted diet
- Head Circumference small for age (Microcephaly)
- Cognitive delay
- Light skin pigmention
VI. Labs
- Identified on Newborn Screen
VII. Management
- Strict low Phenylalanine diet for life
- Infant: Low Phenylalanine formula
- Pregnancy: Monitor Phenylalanine concentrations
- Supplementation
- Tyrosine 25 mg/kg/day
- Amino Acid dosing
- Infant: 3 g/kg/day
- Child: 2 g/kg/day