SHM Converge Scientific Abstract ePoster Gallery-Severe Methemoglobinemia With Dapsone Use in Waldenstrom Macroglobulinemia

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This document is a case report and brief review about <strong>severe methemoglobinemia caused by dapsone</strong> in an elderly woman with <strong>Waldenström macroglobulinemia</strong> undergoing chemotherapy.

An 80-year-old patient developed <strong>1 week of mild dyspnea on exertion, fatigue, palpitations, and lethargy</strong> after starting <strong>bendamustine, rituximab, and dapsone</strong> for Pneumocystis jirovecii pneumonia prophylaxis. She became <strong>hypoxemic despite supplemental oxygen</strong>, with oxygen saturation remaining around <strong>85% even on BiPAP</strong>. Her arterial blood gas showed a <strong>high PaO2 (368)</strong> but a <strong>methemoglobin level of 23.7%</strong>, demonstrating the classic <strong>PaO2-saturation gap</strong> seen in methemoglobinemia. Routine labs were otherwise unremarkable except for hyponatremia and chronic anemia.

She was treated with <strong>methylene blue 1 mg/kg</strong>, which rapidly improved her condition. Repeat testing showed <strong>methemoglobin decreased to 5%</strong>, and her oxygenation improved clinically. <strong>Dapsone was discontinued</strong>.

The report emphasizes that methemoglobinemia should be suspected in patients with <strong>cyanosis or hypoxia that does not respond to oxygen</strong>, especially those taking <strong>dapsone</strong>, particularly <strong>elderly or anemic patients</strong> and those who are immunocompromised. Diagnosis may be missed because symptoms such as dyspnea and confusion are nonspecific, and pulse oximetry/ABG findings can be misleading. <strong>Co-oximetry</strong> is recommended when suspicion is high.

The authors conclude that prompt recognition, stopping the offending drug, and treatment with <strong>methylene blue</strong> are key to preventing complications.

Asset Subtitle

Sasha Singh

Meta Tag

Author List Dhruv Joshi, Irfan Vora, Sasha Singh, Vijay Kata

Category Clinical Vignettes

Concept Methemoglobinemia

Concept Hypoxia

Concept Dapsone

Concept Cyanosis

Concept Co-oximetry

Distinguished Non-Finalist

Presenter Organization Riverside Medical Center

Presenting Author Sasha Singh

Track Adult

Keywords

dapsone

methemoglobinemia

Waldenström macroglobulinemia

bendamustine

rituximab

methylene blue

hypoxemia

co-oximetry

Pneumocystis jirovecii prophylaxis

PaO2-saturation gap

Methemoglobinemia

Hypoxia

Dapsone

Cyanosis

Co-oximetry