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5101: Longitudinal Study of Urea Cycle Disorders


Individuals with UCD cannot remove ammonia, a waste product, from the blood. The purpose of this study is to conduct a longitudinal investigation of the natural history, morbidity, and mortality in people with urea cycle disorders (UCD). A longitudinal study is a research design in which the same subjects are observed repeatedly over a period of time. In this study, we will look at how people with a UCD grow and develop over time and how often they get sick.

The research questions are:

  1. What is the prevalence of specific morbid indicators of disease severity, including hyperammonemia, developmental disabilities, and various long-term kidney and liver effects? What is the fatality rate associated with the various forms of UCD?
  2. What are the correlations between various biomarkers and disease severity and progression?
  3. What is the safety and efficacy of currently used and new UCD therapies?

About this Study

This is a longitudinal study of nearly 1,000 individuals with urea cycle disorders. Those participating in this study will be evaluated every three to twelve months, depending on age and time of diagnosis. Participants two years of age and younger that were diagnosed with UCD within the first four weeks of life will be evaluated every three months. Those who are over two years of age or were diagnosed after four weeks of age will be evaluated every six months. Participants older than 18 years of age or who have had liver transplants will be evaluated once every year. Study data can be collected at one of the UCDC clinical sites (see the participating sites listed on the right) or can be requested from the participant's local metabolic physician.

For each visit, you will be asked to:

  • Keep a log of what you eat for three days and talk to a dietician about what you eat
  • Have a physical exam
  • Fill out a feedback form about your life
  • Give blood (1 to 2 teaspoons)

We will look at your medical records from your local doctor's office so that we can collect information about your medical history. Sometimes you will also have a neuropsychological test so that we can keep track of your intellectual development. The neuropsychological test includes exercises, games and quizzes. These help measure your intelligence, attention span, language skills, visual organization, memory, and learning abilities.

Target Enrollment

To be eligible to participate, you must be an individual with one of the following:

  • NAGS Deficiency
  • CPS I deficiency
  • OTC deficiency
  • AS deficiency (Citrullinemia),
  • AL deficiency (Argininosuccinic Aciduria, ASA)
  • ARG Deficiency (Hyperargininemia)
  • HHH Syndrome or ORNT Deficiency
  • CITR Deficiency (Citrullinemia Type II)
  • or urea cycle disorder highly likely/diagnosis pending

You are not eligible to participate if you have:

  • Hyperammonemia caused by another disorder
  • Rare and unrelated serious comorbidities (e.g. genetic syndrome effecting brain development, such as Down Syndrome, intraventricular hemorrhage in the newborn period and extreme prematurity (<1500 g)

How to participate

In order to participate in a study, you must personally contact the study coordinator of any of the participating institutions by phone or by e-mail.

Current Enrollment

Type of UCDNeonatalLate OnsetTotal
F  38
M 41
F 42
F 0
M 15
F 20
F 50
M 20
F 25
F 1
M 3
F 2
F 14
M 5
F 5
F 1
M 9
F 5
F 2
M 1
F 3
F 6
M 95
F 320
Diagnosis PendingM 2
F 0
M 4
F 2