Severe Neurological Sequelae and Radiological Findings in a Lost-to-Follow-Up Case of Hyperornithinemia-Hyperammonemia-Homocitrullinuria Syndrome

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a rare autosomal recessive urea cycle disorder caused by defective hepatic ornithine transport, leading to hyperammonemia and progressive neurological complications. We report the case of a patient who was treated for hyperammonemic crisis at birth and subsequently diagnosed with HHH syndrome. Management, including ammonia-lowering therapy and a low-protein diet, was initiated; however, due to significant socioeconomic barriers, he was lost to follow-up from the age of two. He re-presented at the age of 12 in a severely debilitated state with global developmental delay and refractory epilepsy. Investigations demonstrated radiological evidence of neurological damage, including corpus callosal atrophy, alongside biochemical and ultrasonographic features of hepatic dysfunction. This case highlights the critical importance of sustained treatment, multidisciplinary follow-up, and adequate social support in preventing irreversible complications of HHH syndrome.