Phenylketonuria is generally associated with severe mental deficiency, but a few untreated patients have been detected with an intelligence quotient above 70. Jervis1 found 3 patients with IQ's above 70 out of 330 patients in whom adequate psychometric data were available. Knox2 recently 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.3 Several excellent reviews of this subject are available.4-6 In brief, phenylketonuria is considered to be an inborn error of protein
ALLEN RJ, GIBSON RM. Phenylketonuria with Normal Intelligence. Am J Dis Child. 1961;102(1):115–122. doi:10.1001/archpedi.1961.02080010117019
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