When methylene blue fails: a case of methemoglobinemia induced by azoxystrobin and propiconazole managed by exchange transfusion.

backgroundMethemoglobinemia is a potentially life-threatening condition resulting from the oxidation of hemoglobin's iron moiety from ferrous (Fe²⁺) to ferric (Fe³⁺). Clinical features include cyanosis unresponsive to oxygen therapy, chocolate-colored blood, and a marked saturation gap between pulse oximetry and arterial blood gas. Methylene blue remains the cornerstone of treatment; however, in rare instances, patients may exhibit refractory responses necessitating advanced interventions. Literature documenting methemoglobinemia due to fungicides like azoxystrobin and propiconazole remains scarce. CASE PRESENTATION: A young female presented with altered sensorium, shock, and hypoxia following the ingestion of a fungicide containing azoxystrobin and propiconazole. Despite a PaO₂ of 400 mmHg on ABG, pulse oximetry showed 83% oxygen saturation, raising suspicion of dyshemoglobinemia. Methemoglobin levels were elevated at 80.7%. She was treated with intravenous methylene blue. While an initial decline in methemoglobin levels to 4% was observed, relapse occurred within 12 h. On day three, therapeutic red blood cell exchange transfusion was performed resulting in a reduction of methemoglobin levels to 14.2%. Despite aggressive measures, she succumbed to refractory shock on day five of admission.

conclusionThis report presents likely the first documented case of fatal methemoglobinemia due to ingestion of azoxystrobin and propiconazole-a combination fungicide widely used in agriculture. The case highlights the limitations of standard therapies like methylene blue in severe poisoning and underscores the need for early consideration of exchange transfusion. With the increasing use of such agents in rural communities, clinicians must maintain vigilance for unusual toxicities and ensure timely escalation in refractory cases.