Table 2

Urea cycle disorders and expected investigation results

Urea cycle disorder	Gene	Inheritance	Plasma amino acids	Urine organic acids
Carbamoylphosphate synthetase I deficiency	CPS1	Autosomal recessive	↓ Arginine ↓ Citrulline	↓/Normal urinary orotic acid
Ornithine transcarbamylase deficiency	OTC	X linked	↓ Arginine ↓ Citrulline	↑ Urinary orotic acid
Argininosuccinic acid synthase deficiency or citrullineamia type I	ASS1	Autosomal recessive	↑ Arginine ↑ Citrulline
Argininosuccinase acid lyase deficiency or argininosucciniaciduria	ASL	Autosomal recessive	↑ Arginine ↑ Citrulline
Arginase deficiency	ARG1	Autosomal recessive	↑↑ Arginine
N-acetylglutamate synthase deficiency	NAGS	Autosomal recessive	↓ Arginine ↓ Citrulline	↓/Normal urinary orotic acid

Plasma amino acid and urinary organic acid levels indicated as being low (↓) or high (↑) relative to the reference range.