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OTC Presentation Variable Presentation of Urea Cycle Disorders

Urea cycle disorders (UCDs) vary in presentations depending on whether they are symptomatic early-onset, symptomatic late-onset, or asymptomatic cases.

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UCD stages

early-onset-urea-cycle-disorder-prevalence-chart

Neonatal Onset Urea Cycle Disorders

Symptomatic neonatal onset UCDs present in the first month of life and account for 26% of UCD cases.1

Early symptoms include lethargy, vomiting, and somnolence but may progress quickly to coma and death.2,3

Symptoms of high ammonia levels in newborns may be misdiagnosed as neonatal sepsis.4 However, initial symptoms often appear after discharge which can delay diagnosis.1,4

lateonsetureacycledisorderprevalencechart 1

Later in Life Urea Cycle Disorders

Later symptomatic onset UCDs present at any age beyond the neonatal period and account for 69% of UCD cases.1

Symptoms of elevated ammonia are subtle and may include headaches, lethargy, confusion, vomiting, and loss of appetite. These nonspecific symptoms can result in delayed diagnosis or misdiagnosis.2

As the UCD remains undiagnosed, patients may experience repeat hyperammonemic attacks which may result in cognitive damage or dysfunction.2

asymptomatic-urea-cycle-disorder-prevalence-chart

Asymptomatic Urea Cycle Disorders

The remaining 5% of UCD cases are asymptomatic with only nonspecific symptoms.1

With the absence of clinical symptoms, the UCD may continue to be undiagnosed or misdiagnosed until a hyperammonemic crisis occurs.2,4 UCD symptoms may begin or advance later in life.2,5

Regardless of presentation and onset of symptoms or patient age, UCDs remain challenging to diagnose.4

1.-Genetic-Testing

Genetic Testing May Help Identify a Defective Gene

Learn more about the Genetic Testing Program at Baylor Genetics. This program offers free testing for individuals who may be carriers of genes associated with urea cycle disorders

Learn About Genetic Testing
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  • References

    1. 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. 2. Cohn RM, Roth KS. Hyperammonemia, bane of the brain. Clin Pediatr (Phila). 2004;43(8):683-689. 3. 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. 4. 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. 5. Legras A, Labarthe F, Maillot F, Garrigue MA, Kouatchet A, Ogier de Baulny H. Late diagnosis of ornithine transcarbamylase defect in three related female patients: polymorphic presentations. Crit Care Med. 2002;30(1):241-244.