Hyperammonaemia. A variant type of deficiency of liver ornithine transcarbamylase.

The specific syndrome arising from an absent or low hepatic ornithine transcarbamylase activity has been termed hyperammonaemia (Russell et al., 1962; Levin and Russell, 1967; Levin, 1968). In the previous communication (Levin et al., 1969) 2 cases occurring in mother and child are described. In this article, we record an infant who during the course of an investigation for the cause of his vomiting had an unexplained episode of illness in which he became lethargic, drowsy, and finally comatose, with convulsions. He was found to have a high plasma and CSF ammonia, and the diagnosis of hyperammonaemia was confirmed by assay of the urea cycle enzymes of the liver. Studies of the properties of the liver ornithine transcarbamylase in this patient suggest that he represents a variant type of deficiency of this enzyme. This may be correlated with the relative mildness of his condition, and the rapidity and completeness of clinical recovery. The effect of citric acid, glutamic acid, alanine, and arginine on plasma ammonia levels was also studied.