characterized by the presence of a higher than normal level of methemoglobin (metHb) in the blood.
Methemoglobin is a form of hemoglobin that does not bind oxygen. When its concentration is elevated in red blood cells, tissue hypoxia can occur.
Normally, methemoglobin levels are <1%, of total blood hemoglobins.
- congenital methemoglobinemia – NADH methemoglobin reductase mutation
- acquired methemoglobinemia –
- exogenous oxidizing drugs and their metabolites
- may accelerate the rate of formation of methemoglobin up to one-thousandfold, overwhelming the protective enzyme systems and acutely increasing methemoglobin levels.