PKU and temperament. Rating children three through seven years old in PKU families

Parents of children with PKU completed behavior rating forms for their children three through seven years old. The 25 completed forms represented 79 percent of the families contacted; 16 of the children had PKU and 9 were siblings of children with PKU. Of the 16 children with PKU, 15 were on phenylalanine-restricted diets at the time of the study. The children with PKU were rated as significantly more rhythmic, more intense, and less persistent than the siblings without PKU. When ratings were compared with those obtained from a private pediatrics practice, children with PKU were significantly less persistent and the siblings were significantly less rhythmic and less intense. There was a significant correlation between blood phenylalanine levels and persistence ratings, with children having higher blood levels tending to be rated as less persistent than children having lower blood levels.