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A subsequent arterial blood gas (ABG) revealed an oxygen saturation (SaO\n                    <jats:sub>2<\/jats:sub>\n                    ) of 95% and a methaemoglobin (MetHb) level of 10.7%. On review of her drug history, it was noted that she was taking 100 mg of dapsone once daily for\n                    <jats:italic>Pneumocystis jirovecii<\/jats:italic>\n                    pneumonia (PCP) prophylaxis. Dapsone was discontinued; her symptoms and hypoxia rapidly improved, and she was discharged 48 hours later.\n                  <\/jats:p>","DOI":"10.1136\/bcr-2025-271307","type":"journal-article","created":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T16:15:33Z","timestamp":1777479333000},"page":"e271307","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Dapsone-induced methaemoglobinaemia: a challenging diagnosis or missed opportunity? 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