Variations in intelligence in phenylketonuria.

pHENYLKETONURIA was originallycalled imbecilitas phenylpyruvica, phenylpyruvic amentia or phenylpyruvic oligophrenia. In time it was realized that although the great majority of patients with phenylketonuria are mentally retarded, a small proportion have normal or near normal intelligence. Furthermore it is now evident that the early treatment of the disease by a low phenylalanine diet will often prevent the appearance of mental retardation.1 Since not all patients with this disease are necessarily retarded and since they all have a similar metabolic disorder characterized by the excretion of phenylketones in the urine, phenylketonuria seems the most appropriate tiUe.2 This paper describes the variations in intelligence of a series of 75 patients with untreated phenylketonuria, including an adult with normal intelligence. Some observations on the effect of a low phenylalanine diet in 12 children are also presented.