Alternative pathway therapy for urea cycle disorders.

In man the major pathway for the disposal of waste nitrogen is the urea cycle; in inborn errors of this pathway, nitrogen flux is reduced. As a result there is accumulation of ammonia and glutamine with disordered metabolism of other amino acids. Nitrogen homeostasis can be restored in these patients with a low-protein diet combined with compounds that create alternative pathways for nitrogen excretion. The introduction of these compounds has been a major advance in the management of these inborn errors and as a result the outcome, particularly for those treated early, has improved.