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. The disease is ornithine translocase deficiency (MONDO_0009393). Also known as: HHH syndrome, ORNT1 deficiency, hyperornithinemia-hyperammonemia-homocitrullinemia syndrome, hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, ornithine carrier deficiency, triple H syndrome.