The purpose of this study is to determine if patients participating in "The Longitudinal Study of Urea Cycle Disorders" are different than participants in the Urea Cycles Disorders Consortium (UCDC) Rare Diseases Clinical Research Network (RDCRN) Contact Registry and to determine if patients are a good source of medical information.

Participants enrolled in the RDCRN UCDC Contact Registry will receive an email inviting them to participate in the study. Interested participants will be directed to the informed consent document. After agreeing to participate, participants will be directed to the study web portal. The study web portal will be developed and maintained by the Data Management and Coordinating Center at the University of South Florida (USF).

Participants will complete several questionnaires about their urea cycle disorder including diagnosis and treatment information and quality of life.

Inclusion Criteria:

• Enrollment in UCDC RDCRN Contact Registry
• Patient reported diagnosis of one of the eight UCDs or UCD diagnosis highly likely/pending.

Exclusion Criteria:

• Cases of hyperammonemia caused by an organic acidemia, lysinuric protein intolerance, mitochondrial disorders, congenital lactic acidemia, fatty acid oxidation defects and primary liver disease.
• Individuals with rare and unrelated serious comorbidities, e.g., Down syndrome, intraventricular hemorrhage in the newborn period, and extreme low birth weight (<1,500 grams).
• Inability to provide informed consent and complete surveys

Patients with urea cycle disorders will be recruited via the RDCRN UCDC Contact Registry. The UCDC contact registry consists of over 300 participants with urea cycle disorders.