citrullinemia type I
Findings
No curated finding names citrullinemia type I yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Citrullinemia type I is a rare autosomal recessive urea cycle defect characterized biologically by hyperammonemia and clinically by progressive lethargy, poor feeding and vomiting in the neonatal form (Acute neonatal citrullinemia type I) and by variable hyperammonemia in the later-onset form (adult-onset citrullinemia type I).
Definition from the Mondo Disease Ontology (MONDO:0008988), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal recessive inheritance
- Onset and course
- Infantile onset · Juvenile onset · Neonatal onset
HPO, annotations 2026-09-02
Features
32 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- Elevated circulating citrulline concentrationHPOHP:0011966
- 15 of 15 reported patients
- Very frequent (80% to 99% of cases)
- HyperglutaminemiaHPOHP:0003217
- 14 of 14 reported patients
- OroticaciduriaHPOHP:0003218
- 14 of 14 reported patients
- Reduced tissue argininosuccinate synthetase activityHPOHP:6000353
- 29 of 29 reported patients
- HyperammonemiaHPOHP:0001987
- Very frequent (80% to 99% of cases)
- Hepatic failureHPOHP:0001399
- Frequent (30% to 79% of cases)
Show the remaining 20
- Moderate intellectual disabilityHPOHP:0002342
- Occasional (5% to 29% of cases)
- Respiratory alkalosisHPOHP:0001950
- Occasional (5% to 29% of cases)
- SeizureHPOHP:0001250
- Occasional (5% to 29% of cases)
- SpasticityHPOHP:0001257
- Occasional (5% to 29% of cases)
- VomitingHPOHP:0002013
- Occasional (5% to 29% of cases)
- Ankle clonusHPOHP:0011448
- Very rare (1% to 4% of cases)
Genes
1 gene
Germline variants in the gene encoding each protein, as classified by GenCC submitters, each in their own words. Limited, disputed and refuted submissions are listed too.
- ASS1HGNC:758
- Definitive · ClinGen · Autosomal recessive · 2018
- Definitive · Natera · Autosomal recessive · 2022
- Definitive · Myriad Women's Health · Autosomal recessive · 2018
- Definitive · G2P · Autosomal recessive · 2015
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal recessive · 2020
- Strong · PanelApp Australia · Autosomal recessive · 2025
Where it sits
- Narrower terms (2)
Other names
8 names
Resolves to: citrullinemia type I
- Also called
- argininosuccinate synthase deficiencyargininosuccinate synthetase deficiencyargininosuccinic acid synthase deficiencyargininosuccinic acid synthetase deficiencyASS deficiencycitrullinemia type 1classic citrullinemiaCTLN1