398 ALBERT S. MORACZEWSKI 



One type of congenital mental deficiency is exemplified by 

 the condition known as phenylpyruvic oligophrenia or as 

 phenylketonuria."^' The first term emphasizes the impairment 

 of the brain or mental function; the second refers to the rela- 

 tively high concentration of phenylpyruvic acid found in the 

 urine of the affected individual. Careful study of many cases 

 has revealed that it is an hereditary disorder of protein meta- 

 bolism mediated by a non-sex-linked recessive gene."'' As a 

 result of this genetic defect, there is a defect of the enzyme 

 system, phenylalanine hydroxylase. Without the proper func- 

 tioning of phenylalanine hydroxylase, there is an excessive 

 accumulation of phenylalanine in the blood and cerebrospinal 

 fluid. The precise manner in which the deleterious effect is 

 brought about is not known. Apparently it is the excess of 

 phenylalanine (or one of its products) which interferes with 

 the proper development of the central nervous system and 

 leads to a consequent mental retardation. If this condition is 

 discovered very early in the infant's life, the development of 

 mental deficiency can be largely prevented by administering 

 a diet free of the offending amino acid."^ 



Another type of mental deficiency resulting from a congenital 

 metabolic defect is cretinism,"^ It should be noted, however, that 

 a primary deficiency in the synthesis of the thyroid hormone is 

 not the only cause of cretinism. It can also arise from other 

 causes of thyroid hypofunction, e. g., from abnormal embryonic 

 development of the thyroid gland or from deficient dietary 



^^ For a general review of this disease see the following: G. A. Jervis, " Phenyl- 

 pyruvic Oligophrenia," in Genetics and the Inheritance of Integrated Neurological 

 and Psychiatric Patterns (Baltimore: Williams & Wilkins, 1954), 259-282; W. E. 

 Knox and D. Y-y. Hsia, " Pathogenic Problems in Phenylketonuria," American 

 Journal of Medicine, XXII (1957) , 687 ff. 



^^ Lippman, op. cit., p. 276; C. Mitoma, R. M. Auld and S. Uudenfriend, " The 

 Enzymatic Defect in Phenylpyruvic Oliogophrenia," Proceedings of the Society for 

 Experimental Biology and Medicine, XCIV (1957), 634. 



^' M. D. Armstrong and F. H. Tyler, " Studies on Phenylketonuria. I: Restricted 

 Phenylalanine Intake in Phenylketonuria," Journal of Clinical Investigation, XXXIV 

 (1955), 565. 



^* Cf. J. B. Stanbury and E. M. McGirr, " Sporadic or Non-Endemic Familial 

 Cretinism with Goiter," American Journal of Medicine, XXlI (1957), 712. 



