Severe hyperlactatemia from Warburg effect due to post-transplant lymphoproliferative disorder after paediatric heart transplantation with resolution following thiamine administration.

Hyperlactatemia is a common and concerning finding in the paediatric cardiac ICU as it may signify tissue hypoperfusion and/or hypoxia. However, it is important to include other aetiologies for an elevated lactate in the differential, especially when the lactate is significantly elevated (> 8 mmol/L). We present the case of metabolic acidosis with severe hyperlactatemia secondary to Warburg effect and presumed thiamine deficiency in a paediatric heart transplant patient with post-transplant lymphoproliferative disorder.