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Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome

Disease definition

Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome (triple H syndrome) is a disorder of urea cycle metabolism characterized by either a neonatal-onset with manifestations of lethargy, poor feeding, vomiting and tachypnea or, more commonly, presentations in infancy, childhood or adulthood with chronic neurocognitive deficits, acute encephalopathy and/or chronic liver dysfunction.


  • Synonym(s):
    • HHH syndrome
    • ORNT1 deficiency
    • Ornithine carrier deficiency
    • Ornithine translocase deficiency
    • Triple H syndrome
  • Prevalence: 1-5 / 10 000
  • Inheritance: Autosomal recessive 
  • Age of onset: Childhood, Adolescent, Adult, Neonatal, Infancy
  • ICD-10: E72.4
  • OMIM: 238970
  • UMLS: C0268540
  • MeSH: -
  • GARD: 2830
  • MedDRA: -

Additional information

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