Hyperornithinemia-hyperammonemia-homocitrullinuria orphanet UMLS:C0268540 Triple H syndrome ICD10:E72.4 HHH syndrome OMIM:238970 Triple H syndrome (hyperornithinemia, hyperammonemia, and homocitrullinuria) is a very rare autosomal recessive genetic disease due to defective transportation of ornithine into the mitochondria. Onset may be neonatal, infantile or juvenile (until adolescence). The initial clinical signs are coma due to hyperammonemia, convulsions, and hypotonia. Disorder of urea cycle metabolism and ammonia detoxification