What is the role of vitamin B12 deficiency in the etiology of macrocytosis?

Updated: Dec 16, 2020
  • Author: Vincent E Herrin, MD, FACP; Chief Editor: Emmanuel C Besa, MD  more...
  • Print
Answer

Vitamin B12 deficiency is a cause of macrocytosis. Because DNA synthesis requires cyanocobalamin (vitamin B12) as a cofactor, a deficiency of the vitamin leads to decreased DNA synthesis in the erythrocyte, thus resulting in macrocytosis. A dietary deficiency of vitamin B12 is rare and usually only occurs in elderly persons on a "tea-and-toast diet" or in strict vegan vegetarians. However, deficiency can result from the following:

  • Lack of intrinsic factor in patients who have undergone gastrectomy or who have pernicious anemia

  • Malabsorption of vitamin B12 secondary to small bowel bacterial overgrowth, tapeworm, familial factors, drugs, ileal bypass, ileal enteritis, or sprue


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!