Asian Research Journal of Current Science

Background: Severe high-anion-gap metabolic acidosis (HAGMA) in early infancy can closely resemble an inborn error of metabolism (IEM), particularly when accompanied by dehydration, shock, respiratory failure, and multisystem biochemical abnormalities. Feeding-related metabolic decompensation should therefore be considered during the differential diagnosis of critically ill young infants.

Case Presentation: A 38-day-old female infant was admitted with respiratory failure, lethargy, shock, and severe failure to thrive after being fed exclusively with unmodified cow and goat milk from day 15 of life following maternal lactation failure. Her weight declined from 2.70 kg at birth to 2.02 kg. Investigations revealed severe HAGMA (pH 7.22, HCO₃⁻ 6.5 mmol/L, anion gap 20.9 mEq/L), hypernatraemia (165.1 mmol/L), profound hypokalaemia, prerenal azotaemia, transaminitis, coagulopathy, and radiographic features consistent with aspiration pneumonitis. Blood ammonia and lactate were within the stated reference ranges, while tandem mass spectrometry showed no metabolic abnormality. Urinary gas chromatography-mass spectrometry was non-diagnostic following resuscitation and alkalinisation. Management included invasive ventilation, controlled fluid and sodium correction, fractionated bicarbonate replacement, potassium supplementation, haemodynamic support, antimicrobial therapy, and progressive nutritional rehabilitation. The infant was extubated on day 4 and discharged weighing 2.33 kg.

Discussion: The clinical and biochemical presentation initially suggested an IEM; however, the rapid correction of metabolic abnormalities with supportive care and appropriate nutrition favoured an acquired feeding-related metabolic collapse. Hypernatraemic dehydration, nutritional deprivation, and aspiration-related respiratory compromise collectively contributed to the severe presentation.

Conclusion: Inappropriate animal-milk feeding in early infancy may produce severe hypernatraemic dehydration and HAGMA that mimic an IEM. Careful biochemical assessment, gradual electrolyte correction, respiratory support, and nutritional rehabilitation are essential for favourable recovery.