One week after the transplant, dapsone therapy was resumed. Nine days into this course of dapsone, the patient developed dyspnea and oxygen desaturation of unknown etiology. The patient was evaluated for and diagnosed with methemoglobinemia. She received two doses of intravenous methylene blue and one dose of oral activated charcoal due to fluctuating methemoglobin concentrations. The elimination of dapsone is not completely understood.
Several case reports of dapsone-induced methemoglobinemia are present in the literature.
Most have occurred in patients who have accidentally or deliberately overdosed. Cases of methemoglobinemia in patients receiving therapeutic doses of dapsone are discussed. Clinicians should be aware of the adverse effects associated with dapsone therapy, and patients with dyspnea and hypoxemia of unclear etiology should be evaluated for methemoglobinemia.