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.