Phenylalanine control and family functioning in early-treated phenylketonuria.

The association between effective metabolic control and patients' intelligence test performance and behavior in phenylketonuria (PKU) has been demonstrated frequently. The present study reexamined this relationship in a population of 41 young children with early-treated PKU, and added a dimension of family investigation to determine relationships between dietary phenylalanine control and patient functioning, family functioning and phenylalanine control, and family functioning and patient functioning. Significant correlations were found between concurrent phenylalanine control and patients' intelligence test scores, and lifetime phenylalanine control and patients' social competence. Parent-report measures of family psychological adjustment, stress, interaction, and socioeconomic status showed no significant association with children's dietary phenylalanine control. Family cohesion and adaptability correlated positively with patients' cognitive performance. Results support a policy of diet continuation in PKU, and suggest that family interaction patterns influence patient functioning. Longitudinal study of family factors in PKU is indicated.