DEFINITION:

A disorder of tyrosine metabolism characterized by the transient build-up of tyrosine and phenylalanine in the blood.

EPIDEMIOLOGY:

• incidence: 0.5-10% of newborn infants
• age of onset:
  • first 2-4 weeks of life
• risk factors:
  • prematurity (low birth weight)
  • high-protein diet in a full term infant
  • M > F

PATHOGENESIS:

• suggested that there is a delayed maturation of p-hydroxyphenyl-pyruvic acid oxidase which catalyzes the conversion of tyrosine to p-OH-phenylpyruvic acid
• most infants come to medical attention because of a positive Guthrie Test

CLINICAL FEATURES:

• most infants are asymptomatic
• symptoms include:
  • difficulty swallowing
  • lethargy
  • poor feeding
  • prolonged jaundice

INVESTIGATIONS:

MANAGEMENT: