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Urea cycle disorders: Clinical features and diagnosis

Brendan Lee, MD, PhD
Section Editor
Sihoun Hahn, MD, PhD
Deputy Editor
Elizabeth TePas, MD, MS


The urea cycle is the metabolic pathway that transforms nitrogen to urea for excretion from the body (figure 1). Deficiency of an enzyme in the pathway causes a urea cycle disorder (UCD). The UCDs [1] are:

Carbamyl phosphate synthetase I (CPSI) deficiency (MIM #237300)

Ornithine transcarbamylase (OTC) deficiency (MIM #311250)

Argininosuccinate synthetase (ASS) deficiency [2] (also known as classic citrullinemia or type I citrullinemia, CTLN1, MIM #215700)

Argininosuccinate lyase (ASL) deficiency [3] (also known as argininosuccinic aciduria, MIM #207900)


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Literature review current through: Sep 2016. | This topic last updated: Oct 21, 2015.
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