Orphanet: Hyperornithinemia hyperammonemia homocitrullinuria syndrome

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Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome

Disease definition

A rare, genetic 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 coagulation defects or other chronic liver dysfunction.


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