Aim and background: Acquired Methemoglobinemia, is one of the least common differential diagnoses while evaluating a cyanotic and hypoxemic patient. Typically results from toxin exposure, leading to significant morbidity and mortality if not promptly diagnosed and treated.
Case description: A 38-year-old woman presented with altered consciousness, and respiratory distress, 13 hours after ingesting emamectin benzoate. She exhibited refractory hypoxemia, cyanosis with a “saturation gap”, and a co-oximetric methemoglobin level of 33%. Treatment included methylene blue infusion, Vitamin C, and N-acetylcysteine. Her mentation and oxygen saturation improved gradually, and she was discharged on the sixth day.
Conclusion: Methemoglobinemia following pesticide ingestion is rare but fatal. Physicians should consider it in cases of refractory hypoxemia and a “saturation gap”. Treatment with antidotes is crucial and continued monitoring is essential to detect and manage potential relapse.
Clinical significance: This is the first case report of methemoglobinemia followed by emamectin benzoate poisoning.
El-Saber Batiha G, Alqahtani A, Ilesanmi OB, et al. Avermectin derivatives, pharmacokinetics, therapeutic and toxic dosages, mechanism of action, and their biological effects. Pharmaceuticals (Basel) 2020;13(8)196. DOI: 10.3390/ph13080196
Godhiwala P, Nirmal A, Bakre A, et al. Acute emamectin benzoate poisoning-a fatal case report. J Evol Med Dent Sci 2020;9(3). DOI: 10.14260/jemds/2020/38
Price D. Methemoglobin inducers. Goldfrank's Toxicologic Emergencies, 11th edition. 2019. pp. 1703–1706, 1715.
George T, Shaikh AI, Thomas L, et al. Severe methemoglobinemia due to insecticide poisoning. Indian J Crit Care Med 2014;18(2):113–114. DOI: 10.4103/0972-5229
Soliman DS, Yassin M. Congenital methemoglobinemia misdiagnosed as polycythemia vera: case report and review of literature. Hematol Rep 2018;10(1):7221. DOI: 10.4081/hr.2018.7221
Ash-Bernal R, Wise R, Wright SM. Acquired methemoglobinemia: a retrospective series of 138 cases at 2 teaching hospitals. Medicine (Baltimore) 2004;83(5):265–273. DOI: 10.1097/01.md.0000141096.00377.3f
Iolascon A, Bianchi P, Andolfo I, et al. Recommendations for diagnosis and treatment of methemoglobinemia. Am J Hematol 2021;96(12):1666–1678. DOI: 10.1002/ajh.26340
Katabami K, Hayakawa M, Gando S, et al. Severe methemoglobinemia due to sodium nitrite poisoning. Case Rep Emerg Med 2016;2016:9013816. DOI: 10.1155/2016/9013816
Liang C, Cui S, Geng L. Hemoperfusion combined with methylene blue in treating methemoglobinemia caused by emamectin benzoate + indoxacarb poisoning: a case report and literature review. Asian J Surg 2023;46(12):5899–5900. DOI: 10.1016/j.asjsur.2023.08.235
Clarke G, Mao J, Fan Y, et al. N-acetylcysteine: a novel approach to methaemoglobinaemia in normothermic liver machine perfusion. Sci Rep 2023;13(1):19022. DOI: 10.1038/s41598-023-45206-z
