Late onset hyperornithinemia, hyperammonemia, and homocitrullinuria syndrome, presenting as recurrent metabolic encephalopathy, A case report

• Published in: Annals of medicine and surgery 2022-12, Vol.84, p.104842, Article 104842
• Main Authors: M A Sarhan, Fajr, Jobran, Afnan W.M., Fayyad, Ali, Ghanim, Zaid, Dweikat, Imad, Elewie, Shireen, Habboub, Ala Mustafa
• Format: Article
• Language: English
• Subjects: Biochemistry; Case Report; Homocitrullinuria; Hyperammonemia; Hyperornithinemia; Late-onset; Rare; Urea-cycle
• ISSN: 2049-0801; 2049-0801
• DOI: 10.1016/j.amsu.2022.104842

and importance: Hyperornithinemia, hyperammonemia, and homocitrullinuria (HHH) syndrome (OMIM 238970) seems to be an autosomal recessive disorder caused by a mitochondrial ornithine transporter 1 deficiency, which results in urea cycle dysfunction. HHH is the most uncommon of the urea cycle diseases, with less than 100 cases recorded. A previously healthy 29 year old male presented to the emergency department complaining of decreased level of consciousness. CT scan, Cerebro-spinal-fluid analysis and toxicology screen were non-significant. Extended serum analysis showed elevated levels of ammonia. Urgent amino acid level analysis showed elevated ornithine. Follow up genetic testing showed that the patient is homozygous for the mutation c.44delG in exon 3 of SLC25A15 gene. In this case, HHH syndrome presented as a late-onset metabolic encephalopathy. For diagnosis; elevated levels of ammonia, ornithine accompanied by the abovementioned genetic mutation confirms the diagnosis. Treatment focuses on reduction of the ammonia levels using sodium benzoat, citrulline or arginine, and low protein diet. HHH syndrome, which is a urea cycle disorder, can present as a late-onset metabolic encephalopathy. High suspicion for genetic causes of metabolic encephalopathy should be maintained even for older patients without prior diagnosis in childhood/adolescence. •Less than 100 cases of Hyperornithinemia-Hyperammonemia-Homocitrullinuria (HHH) syndrome has been reported.•High-index of suspicion for genetic causes for metabolic encephalopathies is to be maintained even in the elderly.•Sodium benzoat, citrulline or arginine, and a low protein diet are cornerstone treatments for HHH syndrome.