Acquired methemoglobinemia in leukemia: Its etiopathogenesis and possible effects on red cell structure and function

Significant methemoglobinemia has been observed in 79% (66/84) cases of leukemia, irrespective of their morphologic types. The mean methemoglobin (Hi) levels were 5.60, 3.22, 4.49 and 2.25% in acute myeloblastic, chronic granulocytic, acute lymphoblastic and chronic lymphocytic leukemia respectively, against the normal mean of 1.10%. Twenty-two cases had values higher than 5% out of which 7 had more than 10% Hi.Strong evidence is presented in this paper to suggest that methemoglobinemia is acquired in leukemia as a result of greatly increased in vivo oxidation of hemoglobin by oxidants generated by the leukemic cells, in spite of a normal Hi-reducing system in the red cells. Higher Hi levels are encountered in the acute leukemias, probably because immature leucocytes produce greater amounts of oxidants compared to the more mature ones. The possible effects of methemoglobinemia and associated red cell membrane lipid and protein peroxidation on the structure and function of red cells are discussed in the light of the pre-existent decreased oxygen carrying capacity of these cells in leukemia due to anemia.