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 > Argininosuccinate synthetase deficiency
Argininosuccinate synthetase deficiency (ASSD)
Alternative Names: Citrullinemia I
Disease Category: Urea Cycle Disorders
An inherited, metabolic, urea cycle disorder characterized by hyperammonemia (high blood ammonia levels) due to deficiency or absence of an enzyme needed to convert nitrogen from protein metabolism (break down) into urea (a waste product). Symptoms include vomiting, feeding and growing problems, fatigue, seizures, hypotonia (low muscle tone), hepatomegaly (enlarged liver), liver failure, respiratory distress, cerebral edema (fluid accumulation increasing pressure around the brain), coma, ataxia (lack of coordination), developmental delay, intellectual disability, and behavioral changes.