RELATIVE INABILITY OF MOTHER AND CHILD TO CONVERT PHENYLALANINE TO TYROSINE - POSSIBLE CAUSE OF NONSPECIFIC MENTAL-RETARDATION

In order to test the hypothesis that hereditary deficiencies in nonessential amino acid synthesis might be an important basis of mental retardation, we looked for associated heterozygosity for phenyketonuria in mother-child pairs among 18 families with nonspecific mental retardation. Although no evidence of phenylketonuria exists in any of these families, 6 showed such association. This represents approximately 30 times chance association and suggests that heterozygosity for phenylketonuria may play a major role in the prenatal development of nonspecific mental retardation. © 1979.