Objective To report 20 cases with phenylketonuria (PKU) detected by neonatal screening program in Thailand

Method Blood samples were collected by filter paper method before the newborns were discharged from the hospital. Elevated blood phenylalanine was identified by the Guthrie test. The diagnosis was confirmed by plasma amino acid analysis and testing for tetrahydrobiopterin deficiency.

Result A total of 5,243,841 newborns were screened, with 16 cases being confirmed as having PKU. 4 additional cases of PKU who were siblings of screening detected cases were not screened. The patients who were diagnosed through the newborn screening program after treatment have a normal growth and development, except 2 cases who subsequently were found to have a 6-pyruvoyl-tetrahydropterin synthase deficiency. Another 4 cases who were not screened presented with delayed development, microcephaly, hypopigmented hair and skin, and one case developed seizure. Although these patients were treated with a phenylalanine restricted diet, all of them had moderate to severe psychomotor retardation.

Conclusion 20 cases of PKU including 16 cases who were detected by the newborn screening program having a good outcome due to early detection and treatment, and 4 cases who were diagnosed later have psychomotor retardation. The results of this study confirm the benefit of early detection and treatment of PKU through the screening program.