5. Patients with urea cycle disorders (UCD): - History of unexplained coma, encephalopathy, or mental retardation - Encephalopathy associated with a protein load - Pregnancy-related or postpartum encephalopathy - History of elevated plasma ammonia or glutamine - Those with cyclical vomiting and lethargy, episodic extreme irritability, ataxia, low BUN, or protein avoidance. - Those with a family history of UCD or unexplained infant deaths (particularly males).