Serum tryptophan to large neutral amino acid ratio and urinary tryptophan in three patients with phenylketonuria in a family. A clinical and biochemical study.

[classical phenylketonuria]

In this work clinical and biochemical findings are presented in three untreated children with phenylketonuria in a family . Their clinical pictures were not typical for classical phenylketonuria . As a result , diagnosis was missed . It has been shown that patterns of large neutral amino acids in serum and urine were somewhat different . Significantly lower serum TRP /LNAA ratio was observed in all patients with phenylketonuria , compared to the control group . These findings suggest that there was subnormal tryptophan availability in the central nervous system leading to its decreased metabolism through the serotonin and kynurenine pathways . These results may explain decreased children 's growth and their mental deficiency .