AN UNDERSTANDING of the nature of the underlying biochemical disorder in hyperammonemia is essential to a rational approach to therapy of this condition. Three types of hereditary enzyme defect in the biosynthesis of urea have been characterized in recent years (Table 1): arginosuccinic aciduria (reaction 4), citrullinuria (reaction 3), and hyperammonemia (reaction 2). It would seem surprising that such a vital metabolic pathway as the Krebs cycle can be blocked and yet the infant survive. This, as well as the fact that children with these defects are still able to produce large amounts of urea, has given rise to considerable discussion,1 yet the problem is still unresolved.
In hyperammonemia, liver ornithine transcarbamylase activity is virtually absent (Table 2). In liver obtained by biopsy in one of our cases, the ornithine transcarbamylase activity was less than 5% the normal, whereas the arginosuccinic acid synthetase and lyase, as well as the
LEVIN B, RUSSELL A. Treatment of Hyperammonemia. Am J Dis Child. 1967;113(1):142-145. doi:10.1001/archpedi.1967.02090160192031