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GTR Home > Conditions/Phenotypes > Congenital hyperammonemia, type I


Carbamoyl phosphate synthetase I deficiency is an autosomal recessive inborn error of metabolism of the urea cycle which causes hyperammonemia. There are 2 main forms: a lethal neonatal type and a less severe, delayed-onset type (summary by Klaus et al., 2009). Urea cycle disorders are characterized by the triad of hyperammonemia, encephalopathy, and respiratory alkalosis. Five disorders involving different defects in the biosynthesis of the enzymes of the urea cycle have been described: ornithine transcarbamylase deficiency (311250), carbamyl phosphate synthetase deficiency, argininosuccinate synthetase deficiency, or citrullinemia (215700), argininosuccinate lyase deficiency (207900), and arginase deficiency (207800). [from OMIM]

Genes See tests for all associated and related genes

  • Also known as: CPSASE1, GATD6, PHN, CPS1
    Summary: carbamoyl-phosphate synthase 1

Clinical features


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Practice guidelines

  • ACMG ACT, 2022
    American College of Medical Genetics and Genomics, Newborn Screening ACT Sheet, Decreased Citrulline, 2022
  • ACMG Algorithm, 2022
    American College of Medical Genetics and Genomics, Algorithm, Decreased Citrulline, 2022
  • ACMG ACT, 2012
    American College of Medical Genetics and Genomics, Transition to Adult Health Care ACT Sheet, Carbamoyl Phosphate Synthetase I (CPS I) Deficiency, 2012

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