Acquired methemoglobinemia from intentional exposure to uncommon agrochemicals: a case series

Introduction Methemoglobinemia is commonly associated with poisoning due to oxidizing compounds. Methemoglobinemia due to agrochemicals is underreported and poses a diagnostic challenge. This report describes five cases of methemoglobinemia from uncommon agrochemicals, highlighting the clinical presentation, management, and associated diagnostic pitfalls.Case A case series of five patients admitted to a tertiary care centre in India after intentional agrochemical ingestion. The causative agents include seaweed extract biostimulant (n = 2), propanil (n = 1), 2,4-D ethyl ester (n = 1), and indoxacarb (n = 1). All patients presented with hypoxia unresponsive to oxygen and a significant saturation gap. The clinical course was variable and included rebound methemoglobinemia, intravascular haemolysis, and acute kidney injury. All patients were managed successfully with intravenous methylene blue and supportive care.Discussion: Differentiating the resultant dry cyanosis from organophosphate toxidromes is critical to prevent iatrogenic anticholinergic toxicity. While methylene blue rapidly resolves direct oxidative stress, agrochemicals requiring metabolic activation necessitate prolonged antidote dosing due to the active metabolites. These compounds demand monitoring for secondary intravascular haemolysis and pigment-induced nephropathy independent of methemoglobin resolution.Conclusion A high index of suspicion when treating poisoning due to unknown agrochemicals is crucial to avoid misdiagnosis of methemoglobinemia and ensure the timely administration of antidote therapy.