Review in-depth insights into the frequency and mechanism of disease for urea cycle disorders (UCDs).
An enzyme or transporter that is missing or defective in the urea cycle may cause a UCD.4 The urea cycle is therefore unable to excrete toxic ammonia resulting in a buildup of ammonia in the blood.3
Elevated levels of ammonia in the body can cause2,5
Presentation of these symptoms can range from asymptomatic to severe depending on the affected enzyme and the extent of the enzyme deficiency.6
UCDs are rare diseases that affect an estimated 1 in 35,000 live births in the United States, though actual incidence may be greater.7
a. Defects in enzyme transporters are often considered UCDs: ornithine translocase deficiency (ORNT1/HHH Syndrome) and citrin deficiency (citrullinemia type II).4,5
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Testing can help confirm a diagnosis
1. Bosoi CR, Rose CF. Identifying the direct effects of ammonia on the brain. Metab Brain Dis. 2009;24(1):95-102. 2. Stone WL, Basit H, Jaishankar GB. Urea Cycle Disorders. StatPearls Publishing; 2022. 3. Matsumoto S, Häberle J, Kido J, Mitsubuchi H, Endo F, Nakamura K. Urea cycle disorders-update. J Hum Genet. 2019;64(9):833-847. 4. Ah Mew N, Simpson KL, Gropman AL, Lanpher BC, Chapman KA, Summar ML. Urea Cycle Disorders Overview. In: Adam MP, Mirzaa GM, Pagon RA, et al., eds. GeneReviews®. Seattle (WA): University of Washington, Seattle; April 29, 2003. 5. Häberle J, Burlina A, Chakrapani A, et al. Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision. J Inherit Metab Dis. 2019;42(6):1192-1230. 6. Summar M, Tuchman M. Proceedings of a consensus conference for the management of patients with urea cycle disorders. J Pediatr. 2001;138(suppl 1):S6-S10. 7. Batshaw ML, Tuchman M, Summar M, Seminara J; Members of the Urea Cycle Disorders Consortium. A longitudinal study of urea cycle disorders. Mol Genet Metab. 2014;113(1-2):127-130.
