Partial ornithine transcarbamylase deficiency associated with recurrent hyperammonemia, lethargy and depressed sensorium

A 6-year-old boy presented with recurrent coma associated with hyperammonemia and infection is reported. A liver biopsy revealed decreased ornithine transcarbamylase (OTC) activity (16% of normal). The enzymatic abnormality in the child is supported by the finding of elevated orotic acid excretion in his mother following a protein load, compatible with an X-linked pattern of inheritance. Since initiation of a dietary arginine supplement, the child has not had recurrent episodes of hyperammonemia.