Contribution of extrahepatic tissues to biochemical abnormalities in hereditary tyrosinemia type I: study of three patients after liver transplantation

Abstract

Three patients with hereditary tyrosinemia type I were examined before and after liver transplantation to assess the role of extrahepatic tissues in the biochemical disorders of this disease. Before transplantation the three patients excreted excessive amounts of succinylacetoacetate (SAA), succinylacetone (SA), tyrosyl acidic compounds, and 5-aminolevulinate (ALA). The activity of 5-aminolevulinate dehydratase (ALA-D) in red blood cells was markedly inhibited (1% to 5% of control) in the three patients. Successful liver transplantation resulted in decreased excretion of urinary SAA plus SA, tyrosyl acidic compounds, and ALA. Two of the patients continued to excrete significant amounts of SAA plus SA, whereas those compounds were undetectable in the urine of the third patient. Tyrosine loading resulted in increased excretion of SAA plus SA in two patients, but those compounds remained undetectable in the third. All three patients continued to excrete higher than normal amounts of ALA, but the activity of ALA-D in red blood cells returned to normal after transplantation, indicating marked clearance of SA from the blood. Liver transplantation may not totally correct the biochemical abnormalities of hereditary tyrosinemia. It is likely that the kidney is the source of persistent biochemical aberrations in the urine without significant effects on the blood. Our results suggest the existence of heterogeneity for renal involvement in hereditary tyrosinemia.