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Evidence for liver disease preceding amino acid abnormalities in hereditary tyrosinemia
Insights
Hereditary tyrosinemia causes liver disease before birth. Postnatal tyrosine elevation suggests treatments targeting tyrosine levels may not be effective for this infant disorder.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Hereditary tyrosinemia is an infant disorder linked to tyrosine metabolism.
- Hepatic toxicity from impaired tyrosine breakdown is suspected to cause liver disease.
Observation:
- Alpha-fetoprotein, a liver disease marker, was high at birth in affected infants.
- Tyrosine levels were normal or not elevated in cord blood.
- High tyrosine levels (hypertyrosinemia) appeared only after birth.
Findings:
- Liver disease in hereditary tyrosinemia is present prenatally.
- Elevated tyrosine levels manifest postnatally, not at birth.
Implications:
- Therapies focused on reducing tyrosine levels may not be fundamentally curative.
- Early diagnosis and prenatal intervention strategies are crucial for hereditary tyrosinemia.
Abstract:
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.