Diseases Studied
The Rare Diseases Clinical Research Network is an NIH-funded research network of 19 active consortia or research groups working to advance treatment for diseases that are rare. Use the search tools on this page to find the diseases we currently study. You can reach out to the indicated consortia or research groups for more information on those diseases and studies underway.
This network focuses on clinical research and does not generally support clinical care outside of research activities. To learn about other rare diseases, please visit the Genetic and Rare Diseases Information Center (GARD), which is an NIH program that helps the public find reliable information about rare and genetic diseases. Their staff are specialists. Contact their specialists through their web form.
All Diseases > Urea cycle disorders
Urea cycle disorders (UCD)
Disease Category: Urea Cycle Disorders
A urea cycle disorder is a genetic disorder that results in a deficiency of one of the six enzymes in the urea cycle. These enzymes are responsible for removing ammonia from the bloodstream. In urea cycle disorders, nitrogen builds up in the blood in the form of ammonia, a highly toxic substance, resulting in hyperammonemia (elevated blood ammonia). Ammonia then reaches the brain through the blood, where it can cause irreversible brain damage, coma and/or death.