[Significance of early detection and early treatment of the development of children with phenylketonuria].

The amino acid l-phenylalanine (PA) accounts for 3-6 percent of all food proteins. Its breakdown is mainly through change into tyrosine. This irreversible metabolic step which makes PA an essential amino acid occurs in the liver and is catalyzed by PA-hydroxylase. In the autosome-recessive phenylketonuria syndrome (PKU, medium incidence rate 1:10,000) there is no PA-hydroxylase activity in the hepatic tissue. Infants suffering from PKU are born without any visible damage, but the untreated disease leads to irreversible brain injury. In the GDR legislation for early screening has been in force since 1971, so that the disease is recognized in all new-born babies. Brain damage can be prevented by dietetic treatment which starts during the first month but not later than the second month of life. The results of examinations performed on 107 infants suffering from PKU, with different onsets of dietetic treatment, underline the fundamental importance of early recognition and treatment for optimal development.