Urea Cycle Disorders

A urea cycle disorder (UCD) is an inherited, inborn error of metabolism present in an estimated 1 in 10,000 births in the United States. Onset may occur at any age depending on the severity of the disorder.

UCDs are caused by a deficiency of one of the enzymes in the urea cycle which is responsible for removing ammonia, a potent neurotoxin. The urea cycle involves a series of biochemical steps in which nitrogen, a waste product of protein metabolism, is removed from the blood and converted to urea which is excreted in the urine. In UCDs, the nitrogen accumulates in the form of ammonia. Left untreated, UCDs can cause dangerously heightened levels of ammonia in the bloodstream (hyperammonemia) resulting in brain damage, coma, and/or death.

The current treatment of urea cycle disorders consists of dietary management to limit ammonia production (with an emphasis on protein restriction and amino acid supplementation) in conjunction with medications and/or supplements which provide alternative pathways for the removal of ammonia from the bloodstream.

This information is adapted from The National Urea Cycle Disorders Foundation (NUCDF), a nonprofit organization dedicated to the identification, treatment and cure of urea cycle disorders. For additional information about UCDs, please contact the NUCDF directly and/or The Urea Cycle Disorders Consortium (UCDC) of the Rare Diseases Clinical Research Network, a National Institutes of Health (NIH)-funded research initiative.