TY - CHAP M1 - Book, Section TI - Methemoglobinemia and Other Dyshemoglobinemias A1 - Prchal, Josef T. A2 - Kaushansky, Kenneth A2 - Prchal, Josef T. A2 - Burns, Linda J. A2 - Lichtman, Marshall A. A2 - Levi, Marcel A2 - Linch, David C. Y1 - 2021 N1 - T2 - Williams Hematology, 10e AB - SUMMARYMethemoglobin is a metalloprotein, in which the iron in the heme group is in the Fe3+(ferric), not the Fe2+(ferrous), state of normal hemoglobin (Hb). Methemoglobinemia occurs because of either increased production of oxidized Hb due to exposure to environmental agents or diminished reduction of oxidized Hb because of underlying germline mutations. Cyanosis occurs when methemoglobin exceeds 15g/L; in comparison, cyanosis is discernible with deoxyhemoglobin at 40g/L and sulfhemoglobin at 5g/L. Hb can also bind carbon monoxide and nitric oxide, resulting in the formation of carboxyhemoglobin and nitrosohemoglobin. Sulfhemoglobinemia occurs because of occupational exposure to sulfa compounds or exposure to oxidants. These modified Hbs are known as dyshemoglobins. Depending on the severity, the presence of dyshemoglobins can result in varying degree of clinical manifestations. Prompt diagnosis is the key to the specific treatment. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - hemonc.mhmedical.com/content.aspx?aid=1180482314 ER -