title: Vitamin B12deficiency from the perspective of a practicing hematologist.
abstract: B12deficiency is the leading cause of megaloblastic anemia, and although more common in the elderly, can occur at any age. Clinical disease caused by B12deficiency usually connotes severe deficiency, resulting from a failure of the gastric or ileal phase of physiological B12absorption, best exemplified by the autoimmune disease pernicious anemia. There are many other causes of B12deficiency, which range from severe to mild. Mild deficiency usually results from failure to render food B12bioavailable or from dietary inadequacy. Although rarely resulting in megaloblastic anemia, mild deficiency may be associated with neurocognitive and other consequences. B12deficiency is best diagnosed using a combination of tests because none alone is completely reliable. The features of B12deficiency are variable and may be atypical. Timely diagnosis is important, and treatment is gratifying. Failure to diagnose B12deficiency can have dire consequences, usually neurological. This review is written from the perspective of a practicing hematologist.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California, Davis, Sacramento, CA.
authors.forename: Ralph
authors.identifier: 0000-0002-9935-230X
authors.initials: R
authors.lastname: Green
mesh_terms: D000749:Anemia, Megaloblastic / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D000752:Anemia, Pernicious / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D005492:Folic Acid / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D014805:Vitamin B 12 / Q000097:blood / Q000378:metabolism*; D014806:Vitamin B 12 Deficiency / Q000150:complications* / Q000378:metabolism* / Q000473:pathology / Q000628:therapy
chemical_list: D005492:Folic Acid; D014805:Vitamin B 12