Acute megaloblastic anemia caused by inhalation of nitrous oxide in a patient with multiple autoimmune pathology.

L Barbosa, I Leal, A T Timóteo, T Matias


Although megaloblastic anemias are generally regarded as chronic conditions of insidious appearance, a megaloblastic state can arise over the course of only a few days due to acute folate or vitamin B12 deficiency. One of the most common causes, though seldom reported, is the nitrous oxide (N02) action in tissue. In fact N02, a volatile substance commonly used in anaesthesia, destroys methylcobalamin, leading to the rapid development of a megaloblastic haematopoiesis. This phenomenon may occur in patients without previous vitamin B12 deficit, but is more frequent and severe when there is a pre-existent deficiency state. A case report is described of a patient with femoral fracture who developed acute anemia after surgery and a latent pernicious anemia was revealed upon investigation.

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