Partial ornithine carbamyl transferase deficiency: an inborn error of the urea cycle presenting as orotic aciduria in a male infant.

Recurrent vomiting without apparent cause should alert the physician to the possibility of a disorder of ammonia metabolism. Crystalluria in a three-month-old male infant with a history of intermittent vomiting since birth and incipient coma led to the discovery of orotic aciduria. A diagnosis of ornithine carbamyl transferase (OCT) deficiency was derived from study of the liver after the infant had died; residual activity was about 5% of normal. Ammonia intoxication was the presumed cause of death. Overproduction of orotic acid and other pyrimidines reflects the deficiency of OCT. The possibility of genetic heterogeneity for the hereditary trait under observation must be considered because it may influence prognosis and counselling.