pediatrics
Tyrosine Metabolism Disorders
Transient tyrosinemia of the newborn
Transient immaturity of metabolic enzymes, particularly 4-hydroxyphenylpyruvic acid dioxygenase, sometimes leads to elevated plasma tyrosine levels (usually in premature infants, particularly those receiving high-protein diets); metabolites may show up on routine Screening Tests for Newborns for Most infants are asymptomatic, but some have lethargy and poor feeding. Tyrosinemia is distinguished from PKU by elevated plasma tyrosine levels. Most cases resolve spontaneously. Symptomatic patients should have dietary tyrosine restriction (2 g/kg/day) and be given vitamin C 200 to 400 mg orally once a day. 