Ainsworth James, Pillai Suresh
Intensive Care Unit, Morriston Hospital, Swansea, UK.
Case Rep Crit Care. 2025 Jun 17;2025:5740399. doi: 10.1155/crcc/5740399. eCollection 2025.
Methamoglobinemia is a condition characterized by impaired oxygen delivery to the tissues due to the formation of methemoglobin (Met-Hb). Diagnosis is established when Met-Hb levels exceed 5%. Levels over 30% are associated with severe symptoms and can be life-threatening. Pulse oximetry may provide misleading readings, often reporting oxygen saturation around 85%, irrespective of actual oxygenation levels. Management involves discontinuing offending agents, providing supportive care, and use of specific treatment agents. Most commonly, cases report a quick and effective recovery following treatment. We describe a case of a patient requiring four separate admissions over a 9-month period, all for methemoglobinemia, where the cause remained uncertain. A 25-year-old female was admitted to the intensive care unit (ICU) with sudden onset shortness of breath and cyanosis, and Met-Hb level 55.5%, suspected due to dapsone. She was treated with 1 mg/kg of methylene blue intravenously. Met-Hb levels remained persistently above 20% for a number of days, and reaccumulated following initial decline. Repeated doses of methylene blue were required, and activated charcoal was given. She was readmitted 3 days later, with reaccumulation of Met-Hb. This was again thought secondary to dapsone, given the long half-life of dapsone and potential for enterohepatic recirculation. She had a third admission with methemoglobinemia almost 2 months after the first admission, and again 8 months later. Suggestion was that azathioprine could be the causative agent; however, this has not been reported previously. We report a case of a 25-year-old female with repeated admissions with methemoglobinemia. This case highlights the potential for refractory methemoglobinemia requiring repeated treatment, and the importance of longer periods of close observation. It is important to consider the diagnosis in patients without a clear trigger for methemoglobinemia, as an identifiable cause may not always be clear.
高铁血红蛋白血症是一种由于高铁血红蛋白（Met-Hb）形成导致组织氧输送受损的病症。当Met-Hb水平超过5%时可确诊。超过30%的水平与严重症状相关，可能危及生命。脉搏血氧饱和度测定可能提供误导性读数，通常报告氧饱和度约为85%，而与实际氧合水平无关。治疗包括停用致病药物、提供支持性护理以及使用特定治疗药物。大多数情况下，病例报告显示治疗后恢复迅速且有效。我们描述了一例患者，在9个月内需要4次单独入院，均因高铁血红蛋白血症，病因仍不确定。一名25岁女性因突发呼吸急促和发绀入住重症监护病房（ICU），Met-Hb水平为55.5%，怀疑是由于服用氨苯砜所致。她接受了1mg/kg的亚甲蓝静脉注射治疗。Met-Hb水平持续数天高于20%，在最初下降后又重新累积。需要重复给予亚甲蓝，并给予活性炭。3天后她再次入院，Met-Hb再次累积。鉴于氨苯砜的半衰期长和肠肝循环的可能性，这再次被认为是氨苯砜所致。首次入院后近2个月，她第三次因高铁血红蛋白血症入院，8个月后又再次入院。推测硫唑嘌呤可能是致病因素；然而此前尚未有相关报道。我们报告了一例25岁女性反复因高铁血红蛋白血症入院的病例。该病例突出了难治性高铁血红蛋白血症需要反复治疗的可能性以及更长时间密切观察的重要性。对于无明确高铁血红蛋白血症诱因的患者考虑该诊断很重要，因为可识别的病因可能并不总是明确的。
