The severity of urea cycle disorders (UCDs) varies based on the position and extent of the enzyme deficiency.1 Proximal defects typically present earlier in life and are more severe than distal defects.1 Variability exists even within each subtype.1,2
Ornithine transcarbamylase (OTC) deficiency, or OTCD, is the most common subtype of urea cycle disorder (UCD).3 Learn more about OTCD here.
Complete deficiencies are characteristic of hyperammonemic crisis shortly after birth and are associated with higher rates of mortality, cognitive impairment, and recurrent crises.1,4
Partial deficiencies are associated with more variable presentations that are observed in later presentations but may occur at any age. However, risk of cognitive effects and premature death is still present.1,4
Review the most common UCD subtype
Access resources for your practice to help in the diagnosis of UCDs
1. 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. 2. National Organization for Rare Disorders (NORD). The Physician’s Guide to Urea Cycle Disorders. Accessed March 23, 2020. https://rarediseases.org/physician-guide/urea-cycle-disorders/ 3. Lichter-Konecki U, Caldovic L, Morizono H, Simpson K. Ornithine transcarbamylase deficiency. In: Adam MP, Ardinger HH, et al, eds. GeneReviews®. Seattle, WA: University of Washington, Seattle; 1993-2019. 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.