RESUMO
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.