Recently acquired knowledge and increased interest in the problems of mental retardation have prompted this presentation on phenylketonuria. Twenty-one patients are reported with a review of the literature. Phenylketonuria may well become a working model for the study of diseases in which psychological abnormalities and multiple biochemical aberrations are the result of a genetically determined enzyme deficiency.
The Norwegian biochemist Fölling first described phenylketonuria in 1934.1 He isolated and crystallized phenylpyruvic acid from the strikingly malodorous urines of two defective siblings. Later, he reported 10 similar patients, noting the lack of clear-cut physical characteristics, a tendency toward dermatoses, muscular rigidity, and an ape-like, or pithecoid, posture. Since phenylpyruvic acid was not found in the urine of normal persons, he related its presence to the mental retardation and named the disease "Imbecillitas Phenylpyruvica." Cases were identified in other European countries and America,2-4 and by 1954 Jervis found 513