Methemoglobin Reductase (MHBR)

Methemoglobin reductase is responsible for keeping hemoglobin in the reduced state in red blood cells. Lack of methemoglobin reductase activity can be the result of acquired or inherited methemoglobinemia. Acquired methemoglobinemia results from exposure to certain drugs and chemicals, and is readily treatable. Infants under four months of age are especially susceptible, as methemoglobin reductase levels are approximately half the adult value. There are two types of inherited methemoglobinemia. The first is an autosomal recessive condition that causes Type I or Type II methemoglobinemia, both the result of defects in methemoglobin reductase. While life expectancy is normal with Type I methemoglobinemia, it is reduced with Type II due to neurological complications which arise. The second type is autosomal dominant, and is the result of a problem with the hemoglobin molecule itself.