Acute Dapsone-Induced Methemoglobinemia in a 24-Year-Old Woman with Ulcerative Colitis

www.turner-white.com M ethemoglobin, a unique form of hemoglobin (Hb) with diminished oxygen affinity, is formed and metabolized roughly at equivalent rates under normal physiologic conditions. However, when methemoglobin generation supersedes compensatory physiologic reductive capacity, methemoglobinemia may result. Potential etiologies of methemoglobinemia include a variety of heritable metabolic defects and acquired insults, with the latter commonly a consequence of exposure to exogenous oxidizing agents. This article reviews the case of a 24-year-old woman who acutely developed methemoglobinemia while being treated with dapsone during an ulcerative colitis (UC) exacerbation. Hb physiology as well as the pathogenesis, diagnosis, and treatment of methemoglobinemia are discussed.