Citrullinemia Type 1

National Organization for Rare Disorders, Inc.

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It is possible that the main title of the report Citrullinemia Type 1 is not the name you expected.

Disorder Subdivisions

  • None

General Discussion

Citrullinemia type I (CTLN1) is a rare autosomal recessive genetic disorder that includes a neonatal acute (classic) form, a milder late-onset form, a form that begins during or after pregnancy, and an asymptomatic form.

CTLN1 is caused by deficiency or absence of the enzyme argininosuccinate synthetase (ASS). ASS is one of six enzymes that play a role in the removal of nitrogen from the body, a process known as the urea cycle. The lack of this enzyme results in excessive accumulation of nitrogen, in the form of ammonia (hyperammonemia), in the blood and all body fluids.

Infants with the classic form may experience vomiting, refusal to eat, progressive lethargy, and show signs of increased intracranial pressure. Prompt treatment can prolong survival, but neurologic deficits are usually present. The course of the late-onset form is sometimes milder but episodes of hyperammonemia are similar to the classic form.

Supporting Organizations

American Kidney Fund, Inc.

11921 Rockville Pike
Suite 300
Rockville, MD 20852
Tel: (800)638-8299

CLIMB (Children Living with Inherited Metabolic Diseases)

Climb Building
176 Nantwich Road
Crewe, CW2 6BG
United Kingdom
Tel: 4408452412173
Fax: 4408452412174

Genetic and Rare Diseases (GARD) Information Center

PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311

National Kidney Foundation

30 East 33rd Street
New York, NY 10016
Tel: (212)889-2210
Fax: (212)689-9261
Tel: (800)622-9010

National Urea Cycle Disorders Foundation

75 South Grand Avenue
Pasadena, CA 91105-1602
Tel: (626)578-0833
Fax: (626)578-0823
Tel: (800)386-8233

Save Babies Through Screening Foundation

P.O. Box 42197
Cincinnati, OH 45242
Tel: (610)251-9876
Fax: (610)647-5757
Tel: (888)454-3383

Urea Cycle Disorders Consortium

Children's National Medical Center
111 Michigan Avenue, NW
Washington, DC 20010
Tel: (815)333-4014

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). For a full-text version of this report, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report.

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

Last Updated:  3/17/2016
Copyright  2013 National Organization for Rare Disorders, Inc.