Congenital hyperammonemic syndromes.

Urea cycle disorders and other hyperammonemic syndromes should be considered in the differential diagnosis in newborns with a history of severe vomiting, lethargy, and seizures, and in infants with feeding problems, episodic vomiting, and altered consciousness. Although the acute neonatal forms of urea cycle disorders are almost always lethal, several of the subacute forms of hyperammonemic syndromes respond favorably to early treatment.