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Hypomorphic citrullinaemia due to mutated ASS1 with episodic ataxia
  1. Arushi Gahlot Saini,
  2. Savita Attri,
  3. N Sankhyan,
  4. Pratibha Singhi
  1. Depatment of Pediatrics, Post Grad Inst Med Educ, Chandigarh, India
  1. Correspondence to Professor Pratibha Singhi, doctorpratibhasinghi{at}


Children with citrullinaemia commonly present in the neonatal period with life-threatening hyperammonaemia and progressive encephalopathy. Less often, ‘hypomorphic’ or mild late-onset childhood or adult-onset forms may be seen with intermittent neurological symptoms or acute crisis in pregnancy. We describe an 11-year-old boy with late-onset citrullinaemia manifesting as brief episodes of ataxia triggered by minor febrile illnesses, significant citrullinaemia, mild hyperammonaemia, normal neurological examination and mild cerebellar atrophy. Targeted gene sequencing showed a homozygous, missense mutation c.815G>A (p.R272H) in exon 12 of ASS1 gene resulting in the amino acid substitution of histidine for arginine at codon 272. Our case highlights the importance of recognising urea cycle defects as a cause of intermittent neurological symptoms such as ataxia. Type-1 citrullinaemia may remain hypomorphic and needs a high index of suspicion.

  • Neuro Genetics
  • Nutrition And Metabolism

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  • Contributors AGS: patient management, draft of manuscript and review of literature. SA: analysis and interpretation of biochemical data and manuscript editing. NS: critical review of manuscript for intellectual content. PS: clinician-in-charge and critical review of manuscript for intellectual content and final approval of the version to be published.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.