Methemoglobinemia

Methemoglobinemia is a condition of altered hemoglobin affinity for oxygen caused by oxidation of heme iron from the ferrous (Fe2+) state to the ferric (Fe3+) state. The majority of methemoglobinemia cases are attributed to exogenous substances that function as oxidizing agents, while only a minority are of congenital origin. Although an infrequent cause of hypoxia, if left untreated, severe methemoglobinemia can be lethal.