In hereditary tyrosinemia, an autosomal recessive disorder of infants, it has been postulated that hepatic toxicity arising from defective degradation of tyrosine accounts for the severe liver disease that is a feature of this condition. We measured the concentration of alpha-fetoprotein, a marker for liver disease, and of amino acid in cord blood from three infants with hereditary tyrosinemia and found that the concentration of alpha-fetoprotein was greatly increased at birth, whereas the level of tyrosine was normal or not specifically elevated, and that hypertyrosinemia developed only postnatally. These results indicate that liver disease is prenatal in hereditary tyrosinemia and that therapy aimed at reduction of the elevated tyrosine level is unlikely to be of fundamental value.
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