Longitudinal Study of Urea Cycle Disorders
This long-term observational study follows children and adults with urea cycle disorders over time to better understand disease progression, treatment outcomes, growth, and cognitive health. CanPKU+ is classifying this study as Recruiting in Canada because a Toronto SickKids site has been listed as recruiting.
Study overview
Official study title: Longitudinal Study of Urea Cycle Disorders
Condition: Urea Cycle Disorders
Study focus: Long-term follow-up of disease progression, treatment, growth, and cognitive outcomes
Sponsor / responsible party: Andrea Gropman, Children's National Research Institute
Study type: Observational
ClinicalTrials.gov ID: NCT00237315
Estimated enrollment: 1,500 participants
Last checked by CanPKU+: March 10, 2026
If you notice that this information is out of date, please let us know at website@canpku.org.
Who may qualify
According to the official study record, this study is open to individuals with a diagnosed urea cycle disorder or strong clinical evidence suggesting a urea cycle disorder. The study includes both pediatric and adult participants.
Because this is a natural history study, the purpose is not to test a new drug. Instead, researchers collect information over time to better understand how UCDs affect health, development, and day-to-day life.
Important: Final eligibility is always determined by the study team.
Canadian site information
Current CanPKU+ classification: Recruiting in Canada
Canadian site:
The Hospital for Sick Children
Toronto, Ontario, Canada M5G 1X8
Principal Investigator listed in recruitment sources: Andreas Schulze, MD
For sites outside Canada: Please use the official ClinicalTrials.gov record below for the most current list of locations and study contacts.
Study background and why it matters
Urea cycle disorders are rare genetic conditions that affect how the body removes ammonia, a waste product of protein metabolism. When ammonia builds up, it can cause serious illness and may affect brain health, especially during metabolic crises.
This study is designed to better understand the natural history of UCDs across a large group of participants. Researchers are assessing biochemical status, growth, survival, and cognitive outcomes over time.
The study also evaluates outcomes associated with different treatment approaches, including alternate pathway therapy and transplantation, and looks for biochemical changes that may help predict future metabolic imbalance before symptoms become severe.
Official study record and links
For the most current status, site list, and eligibility details, use the official study record.
Development history and publications
This section highlights the longer-term research context for this study. It is intended as a plain-language research history summary and does not replace the official study record.
Study history
Study start: February 2006
Estimated primary completion: July 2025
Estimated study completion: July 2026
Research aim: To follow a large cohort of individuals with urea cycle disorders over time
Main outcomes of interest: Disease progression, treatment outcomes, survival, growth, and cognitive function
Why this matters: Natural history studies help improve future clinical trials, support treatment planning, and strengthen understanding of long-term outcomes in rare disorders.
Publications and related research
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Health-related quality of life in a systematically assessed cohort of children and adults with urea cycle disorders, based on participants enrolled in the Longitudinal Study of Urea Cycle Disorders.
View publication -
Unraveling the Link: Seizure Characteristics and Ammonia Levels in Pediatric Urea Cycle Disorders, using data from individuals enrolled in the UCDC Longitudinal Study.
View publication -
Official ClinicalTrials.gov record for the study.
View official study record
If you notice that this section is missing a publication or no longer reflects the latest study history, please let us know at website@canpku.org.