Urea Cycle Disorders.

In the urea cycle, six enzymes are required to convert ammonia to urea: N-acetylglutamate synthetase (NAGS), carbamoylphosphate synthetase (CPS), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS), argininosuccinate lyase, and arginase. Deficiency of any of these enzymes may cause disease. Such infants are asymptomatic for 1-5 days but then feed poorly, vomit, and become lethargic. They may be irritable, rigid, and convulse. They exhibit hyperpnea and respiratory alkalosis, hepatomegaly, and jaundice; and they may have brain edema with bulging fontanels. Death ensues without treatment. [ABSTRACT FROM AUTHOR]