The most common cause of acquired methemoglobinemia is dapsone toxicity. There are no definitive guidelines for the
management of treatment-refractory methemoglobinemia or when methylene blue therapy is contraindicated. We present a case
of recurrent acquired methemoglobinemia that was successfully treated with automated red blood cell exchange. Our patient
was a female patient in her twenties with dapsone-induced methemoglobinemia complicated by hemolytic anemia secondary to
high-dose intravenous vitamin C therapy. She first presented to the emergency department with a two-day history of progressive
dyspnea, chest pain, cyanosis of lips and fingers, nausea, and headache. Given her prior history of severe methylene blue allergy,
the patient was initially treated with intravenous vitamin C and simple transfusions. Her methemoglobin levels increased, and
her symptoms remained. An automated red blood cell exchange resulted in a 42% relative decrease in methemoglobin level
(from a level of 24.1% to 14%) and significant symptomatic improvement within hours of the exchange. While current
therapeutic apheresis guidelines do not recommend red blood exchange for methemoglobinemia due to scarce evidence, this case
report illustrates the potential role of red blood cell exchange in the management of acquired methemoglobinemia in a patient
with severe methylene blue allergy for whom intravenous vitamin C therapy failed.