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Case 2: Cyanosis in a Patient with AIDS

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C Stop dapsone and administer intravenous methylene blue.

This answer is correct. The patient’s dyspnea with a low oxygen saturation despite a high PaO2, gray-brown color (often referred to as “chocolate cyanosis”), and brown-appearing blood all suggest a diagnosis of methemoglobinemia. Laboratory studies revealed an elevated methemoglobin concentration (34%). Dapsone is a common cause of methemoglobinemia and this patient’s clinic history is highly suggestive of this diagnosis. The treatment for methemoglobinemia is intravenous methylene blue and it is generally indicated with a methemoglobin concentration greater than 30% in an asymptomatic patient or if greater than 20% in a patient with symptoms.

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