Ornithine plays a key metabolite in the hepatic ornithine cycle,[15] a five‐step enzymatic pathway.[16] Ornithine transcarbamylase (OTC), a liver‐specific enzyme, directly catalyzes the breakdown of ornithine, and an impaired ornithine cycle caused by a deficiency in OTC results in hyperornithinemia.[17, 18] Patients with hyperornithinemia‐hyperammonemia‐homocitrullineuria (HHH syndrome) usually present with cognitive deficits, hypotonia, and other symptoms of neurological impairment. This evidence concerns the gene OTC and Cognitive impairment.