What causes acquired methemoglobinemia and what are risk factors?

Updated: Dec 09, 2018
  • Author: Mary Denshaw-Burke, MD, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Acquired methemoglobinemia is usually due to the ingestion of drugs or toxic substances. Exposure to such substances in amounts that exceed the enzymatic reduction capacity of RBCs precipitates symptoms. [14] Acquired methemoglobinemia is more frequent in premature infants and infants younger than 4 months, and the following factors may have a role in the higher incidence in this age group:

  • Fetal hemoglobin may oxidize more easily than adult hemoglobin
  • The level of NADH reductase is low at birth and increases with age; it reaches adult levels by age 4 months
  • Higher gastric pH in infants may facilitate bacterial proliferation, resulting in increased conversion of dietary nitrates to nitrites
  • An association between methemoglobinemia and acute gastroenteritis in infants has been noted in several studies. This may be due to acidosis from loss of stool bicarbonate, which impairs the already immature function of the methemoglobin reductase system in these young patients

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