The frequency of PKU and hyperphenylalaninemia in Sweden - a study in institutions for the mentally retarded as well as in neonates.

In a country-wide screening examination in Sweden, PKU was observed in 75 (4.5 per 1,000) and hyperphenylalaninemia in 14 (0.8 per 1,000) of a total of 16,805 patients in institutions for the mentally retarded. In the national neonatal screening program in 1965-1975, which covered nearly 1 million individuals, PKU was observed in 36 and hyperphenylalaninemia in 19 individuals. The incidences of PKU and hyperphenylalaninemia in newborns are calculated to be 1/26,000 and 1/50,000, respectively. In addition, PKU and hyperphenylalaninemia were diagnosed in 14 and 1 non-institutionalized individuals, respectively, born before September 1965. The total numbers of individuals detected as having PKU and hyperphenylalaninemia in Sweden in the present investigation are 125 and 34, respectively.