RESUMEN
A man in his late 60s with a history of well-controlled type 2 diabetes and hepatic cirrhosis presented to the emergency department due to uncontrollable hyperglycaemia following the initial brentuximab vedotin (BV) infusion. BV was initiated as a treatment for mycosis fungoides, a form of cutaneous T-cell lymphoma. The patient was diagnosed with severe hyperglycaemia with ketosis. Empiric treatment with amoxicillin-clavulanic acid, hydration and intravenous insulin infusion was initiated. Hyperglycaemia persisted despite receiving massive amounts of insulin and was corrected only after treatment with high-dose methylprednisolone for suspected type B insulin resistance. Extremely high and difficult-to-treat hyperglycaemia is a rare side effect of BV. Unfortunately, the patient died of upper gastrointestinal bleeding 22 days after discharge. In patients with obesity and/or diabetes mellitus, the blood glucose levels should be carefully monitored when treated with BV.