Aniza Mohammed JelaniHani Ajrina ZulkefleeNoor Azlin Azraini Che SohJulia OmarWan Aireene Wan AhmedMuhammad Yusoff Mohd Ramdzan2024-05-302024-05-3020222022-12-30Aniza Mohammed Jelani, Hani Ajrina Zulkeflee, Noor Azlin Azraini Che Soh, Julia Omar, Wan Aireene Wan Ahmed, & Muhammad Yusoff Mohd Ramdzan. (2022). Severe Hyperammonaemia with Metabolic Acidosis in a Neonate: a Case Report of Ornithine Transcarbamylase Deficiency (OTCD). Malaysian Journal of Science Health & Technology, 8(1), 38–43. https://doi.org/10.33102/20222092601-00032054-210.33102/2022209https://mjosht.usim.edu.my/index.php/mjosht/article/view/209https://oarep.usim.edu.my/handle/123456789/15413Vol. 8 No. 1 (2022)Ornithine transcarbamylase (OTC) deficiency (OTCD), the most common urea cycle disorder, is an X-linked genetic disorder due to complete or partial lack of the OTC enzyme. Its clinical presentation depends on the degree of enzyme deficiency and ranges from an acute neonatal metabolic crisis with a high mortality rate through to an asymptomatic adult. We present a case of a newborn baby boy who presented with poor feeding, vomiting, lethargy, and respiratory distress. Laboratory investigations revealed severe hyperammonaemia, hyperglutaminaemia, hyperalaninaemia, absence of citrulline, and marked orotic aciduria. Family screening confirmed the presence of an OTC disease-causing mutation in his mother. It was a heterozygous mutation, c.316G>A. p. Gly106Arg in exon 4.enurea cycle disorder, OTC, hyperammonaemia, neonateArticle384381(Feb)