Longitudinal Study of Urea Cycle Disorders


Urea cycle disorders (UCD) are a group of rare inherited metabolism disorders. Infants and children with UCD commonly experience episodes of vomiting, lethargy, and coma. The purpose of this study is to perform a long-term analysis of a large group of individuals with various UCDs. The study will focus on the natural history, disease progression, treatment, and outcome of individuals with UCD.

Study Start Date

February 2006

Estimated Completion Date

December 2019


No interventions cited


  • Pediatrics: Nephrology/Urology
  • Endocrinology: Metabolism and Growth
  • Nephrology: Fluids and Electrolytes

MeSH Terms

  • Amino Acid Metabolism
  • Brain Diseases
  • Urea Cycle Disorders

Study ID

Office of Rare Diseases (ORD) -- RDCRN 5101



Trial ID


Study Type


Trial Phase

Phase 2

Enrollment Quota



Office of Rare Diseases (ORD)

Inclusion Criteria

  • Diagnosis of NAGS deficiency, defined as the detection of a pathogenic mutation or decreased (less than 20 % of control) NAGS enzyme activity in liver
  • Diagnosis of CPS I deficiency, defined as decreased (less than 20 % of control) CPS I enzyme activity in liver or an identified pathogenic mutation
  • Diagnosis of OTC deficiency, defined as the identification of a pathogenic mutation, linkage analysis in an affected family, less than 20% of control of OTC activity in the liver, or elevated urinary orotate (greater than 20 uM/mM) following allopurinol loading with absence of argininosuccinic acid
  • Diagnosis of AS deficiency (Citrullinemia), defined as a greater than or equal to 10-fold elevation of citrulline in plasma, decreased AS enzyme activity in cultured skin fibroblasts or other appropriate tissue, or identification of a pathogenic mutation in the AS gene
  • Diagnosis of AL deficiency (Argininosuccinic Aciduria, ASA), defined as the presence of argininosuccinic acid in the blood or urine, decreased AL enzyme activity in cultured skin fibroblasts or other appropriate tissue, or identification of a pathogenic mutation in the AL gene
  • Diagnosis of ARG deficiency (Hyperargininemia), defined as a greater than or equal to 5-fold elevated arginine levels in the blood, decreased arginase enzyme levels in red blood cells or other appropriate tissue, or identification of a pathogenic mutation in the ARG gene
  • Diagnosis of HHH Syndrome or ORNT deficiency, defined as a greater than or equal to 5-fold elevated plasma ornithine and homocitrulline levels in the urine, or a pathogenic mutation in the ORNT1gene (SLC25A15)
  • Diagnosis of CITR deficiency (Citrullinemia Type II), defined as elevated citrulline levels in the blood and a pathogenic mutation in the citrin gene
  • Pending diagnosis of a UCD, defined as laboratory values highly suggestive of a UCD with symptomatic hyperammonemic episodes but without a verifiable diagnosis

Exclusion Criteria

  • Hyperammonemia caused by an organic academia, lysinuric protein intolerance, mitochondrial disorder, congenital lactic academia, fatty acid oxidation defects, or primary liver disease
  • Rare and unrelated comorbidities (e.g., Down's syndrome, intraventricular hemorrhage in the newborn period, and extreme prematurity)





Accepts Healthy Volunteers


Study Locations and Contact Information (11)

Study Location Distance Name Phone Email
Childrens Hospital Boston UCDC New England Center - Boston, Massachusetts 2.6 miles Vera Anastasoaie 617-355-7346 Vera.Anastasoaie@childrens.harvard.edu
Icahn School of Medicine at Mount Sinai - New York, New York 183.2 miles Luca Fierro 212-659-1477 luca.fierro@mssm.edu
Childrens Hospital of Philadelphia - Philadelphia, Pennsylvania 270.8 miles Irma Payan RN 215-590-6236 Payan@email.chop.edu
Childrens National Medical Center - Washington, District of Columbia 391.7 miles Kara Simpson MS CGC 202-476-6216 ksimpson@childrensnational.org
Case Western Medical College - Cleveland, Ohio 544.0 miles Audrey Lynn PhD 216-844-7124 Audrey.Lynn@UHhospitals.org
University of Minnesota - Minneapolis, Minnesota 1,120.0 miles Susan Berry MD None berry002@umn.edu
Baylor College of Medicine - Houston, Texas 1,609.9 miles Mary Mullins RN BSN 832-822-4263 mullins@bcm.edu
Childrens Hospital Colorado - Aurora, Colorado 1,759.8 miles Curtis Coughlin MS CGC 303-724-2310 Coughlin.Curtis@tchden.org
Childrens Hospital and Regional Medical Center - Seattle, Washington 2,487.2 miles Linnea Brody BS MPH 206-987-3694 linnea.brody@seattlechildrens.org
Oregon Health and Science University - Portland, Oregon 2,538.3 miles Julie Martin 503-494-5313 martijul@ohsu.edu
University of California Los Angeles - Los Angeles, California 2,605.2 miles Kim Arang MS LCGC 310-206-6581 arangkim@mednet.ucla.edu

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