Intellectual deficits after transient tyrosinemia in the term neonate.

In order to determine if prolonged, significant transient neonatal tyrosinemia (TNT) is injurious to the developing central nervous system, 15 term infants who had suffered from this disorder for a mean duration of 50 days underwent comprehensive psychometric evaluations at a mean (+/- 1 SD) age of 56.5 +/- 7.8 months. Their mean maximum detected tyrosine level had been 25.8 mg/dl (range, 13.6 to 42.0) and their defect was considered secondary to a combination of a high protein formula intake and a lack of supplemental vitamin C. Compared to a control group, significantly lower mean scores were obtained by the TNT group on the McCarthy Scale of Children's Abilities (77.1 vs. 92, P = .008) and the Illinois Test of Psycholinguistic Ability (92.3 vs. 109.9, P = .002). Performance scores varied inversely with the duration of TNT. Although these children are not classifiable as "mentally retarded," TNT may cause specific learning disabilities. There is, therefore, a need to determine the frequency of TNT in infants fed evaporated milk and other high-protein milk formulas and to develop ways to prevent its occurrence.