Citrullinemia: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 2, 2026.
What kind of doctor treats Citrullinemia?
A primary care doctor often coordinates care. Most patients also see a metabolic specialist, usually a medical geneticist, and a dietitian. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is citrullinemia?
Citrullinemia is a rare inherited condition in which the body cannot remove ammonia, a waste product made when protein is broken down. Ammonia builds up in the blood and can harm the brain and other organs. It is present from birth, and treatment focuses on keeping ammonia levels low.
Citrullinemia is a urea cycle disorder. The urea cycle turns ammonia into urea, which leaves the body in urine. In citrullinemia, one enzyme in this cycle does not work, so ammonia collects in the blood. These high levels, called hyperammonemia, can cause serious illness if not treated quickly.
Symptoms
In babies, symptoms often start in the first days of life and include sleepiness, poor feeding, vomiting, irritability, and seizures. In older children and adults, especially with type II, symptoms may include confusion, unusual behavior, headaches, and loss of appetite.
Causes and who gets it
Citrullinemia is caused by changes in a gene, usually the ASS1 gene for type I or the SLC25A13 gene for type II. A child inherits one changed gene from each parent, who are usually carriers without symptoms. It affects both sexes and is rare.
How doctors diagnose it
Most cases are found through newborn screening, which uses a small blood sample in the first days of life. Doctors confirm it with blood tests measuring ammonia and certain amino acids; genetic testing identifies the exact gene change and type.
Treatment
Treatment keeps ammonia levels low through a low-protein diet, special formulas and supplements, and medicines that help remove ammonia. Some people need a liver transplant if diet and medicines are not enough. Care is lifelong and guided by a metabolic specialist.
When to see a doctor
A baby who is unusually sleepy, vomiting, refusing to feed, or having seizures needs emergency care right away. Anyone with citrullinemia who develops vomiting, confusion, or unusual behavior should contact their care team immediately.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance; a concierge doctor usually charges more and often works alongside insurance. Either can be a helpful partner, offering longer appointments and easier access for diet questions, sick day planning, and routine monitoring. They can manage stable patients and will refer to a metabolic specialist or hospital team when ammonia symptoms appear.
Common questions
Is citrullinemia curable?
There is no cure for the gene change that causes citrullinemia. Treatment can usually keep ammonia under control, and many people do well with careful management. Outcomes depend on the type and how early treatment begins.
Can adults get citrullinemia?
Yes. Citrullinemia type II can first appear in teens or adults. It sometimes causes confusion or behavior changes rather than the classic baby symptoms. Anyone with unexplained episodes like these should talk to a doctor.
Can citrullinemia be found before symptoms start?
Yes. Most newborns in the United States are screened for citrullinemia with a blood test in the first days of life. Finding it early allows treatment to begin before ammonia builds up.
Do people with citrullinemia need to avoid protein completely?
No. The body still needs some protein to grow and stay healthy. A dietitian sets a careful protein limit and may prescribe special supplements.
Sources
- MedlinePlus Genetics - Citrullinemia
- NIH Genetic and Rare Diseases Information Center - Citrullinemia type I
- National Organization for Rare Disorders (NORD) - Citrullinemia Type 1
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
