Methemoglobinemia natural history, complications and prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aksiniya Stevasarova, M.D.

Depending on the causes that have led to methemoglobin formation, different complications and prognosis are expected respectively. Death is the most serious complications of methemoglobinemia especially when MetHb levels approach 70%. In severely sick patients death may occur even with lower levels of MetHb.

• Patients with hereditary forms of methemoglobinemia are generally asymptomatic, with the exception of having chronic cyanosis. Unfortunately, despite the benign nature of the congenital methemoglobinemia, people with type IIb5 cytochrome-reductase deficiency have poor prognosis and shorter lifespan, mainly due to neurologic complications.

• In acquired methemoglobinemia, depending on the amount and duration of toxin exposure, the levels of MetHb in the blood will be different. As a result we expect different outcomes, which are as follows: MetHb of 15% presents with skin and blood color changes at levels; levels above 15% will result in hypoxia and levels above 70% can lead to death. ^{[1] [2]}

• Death is the most serious complications of methemoglobinemia especially when MetHb levels approach 70%. In severely sick patients death may occur even with lower levels of MetHb.
• Other complications include myocardial infarction, seizure and coma. ^[2]

• Depending on the anoxic end-organ damage caused by MetHb, the prognosiss varies between mild and fatal. ^[1]

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