Phenylketonuria with Normal Intelligence

Abstract

Phenylketonuria is generally associated with severe mental deficiency, but a few untreated patients have been detected with an intelligence quotient above 70. Jervis¹found 3 patients with IQ's above 70 out of 330 patients in whom adequate psychometric data were available. Knox²recently listed 20 patients having "high grade" intelligence. Although there is considerable variability in the manifestations of phenylketonuria, probably the most consistent feature is mental deficiency. Studies of relatively large untreated populations of patients with phenylketonuria reveal a variable incidence of the other signs and symptoms, such as eczema, seizures, light hair, and blue eyes.³Several excellent reviews of this subject are available.^4-6In brief, phenylketonuria is considered to be an inborn error of protein