Abstract
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.
Highlights
Severe hyperammonaemia is a life-threatening event in neonates
Our patient presented with hyperammonaemia and metabolic acidosis, which may have misled us to the organic acidaemia diagnosis
Metabolic acidosis can occur in decompensated urea cycle disorder (UCD) due to accumulation of lactic acid secondary to hypoxic tissue injury, as seen in this case evidenced by severe lactic aciduria in urine organic acid [7]
Summary
Severe hyperammonaemia is a life-threatening event in neonates. The underlying aetiologies can be classified into primary (metabolic disorders—urea cycle defect, fatty acid oxidation defect, organic acidaemia) and secondary (liver injury due to infection or toxins, transient hyperammonaemia of the prematurity) categories. CASE REPORT A 72-hour-old baby boy presented with a history of poor feeding associated with persistent vomiting, lethargy, and increasing respiratory distress He developed seizures at the emergency department and was subsequently intubated. Plasma amino acids showed marked elevation of glutamine, alanine, and lysine, with absence of citrulline (Table 2) This was highly suggestive of UCD, and possibly OTCD. His liver function worsened, and he developed coagulopathy His ammonia remained in refractory status despite him receiving chelation with sodium phenylbutyrate and L-arginine as well as peritoneal dialysis. His condition deteriorated further, and he required high ventilator settings, maximum inotropes, and regular blood product transfusion.
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