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Megaloblastic Anemias: Learning Objectives

Medical Importance

Megaloblastic anemias are characterized by morphologic changes resulting from pathologic impairment of DNA synthesis. Most often, these anemias result from deficiencies of folate and/or vitamin B12. When evaluating a patient with megaloblastic anemia, it is crucial to determine which of these vitamins is actually deficient and to define the disease state responsible for the deficiency.

Objectives

  1. List the causes of macrocytic anemia.
  2. Describe the morphologic hallmarks of megaloblastic erythropoiesis and granulopoiesis in the blood and bone marrow.
  3. Diagram the biochemical pathway which explains how folate and vitamin B12 deficiency ultimately impair thymidylate synthesis, and methionine and fatty acid metabolism.
  4. Identify the dietary sources of vitamin B12 and folate and to describe their associated sites and mechanisms of absorption, means of transport, and duration and location of storage.
  5. Describe the differences between vitamin B12 deficiency and folate deficiency with respect to:
    • their most common causes
    • time to development of the clinical deficiency state
    • presence of neurologic and neuropsychiatric abnormalities
  6. Describe the clinical, laboratory and autoimmune findings associated with pernicious anemia.
  7. List the appropriate therapies for B12 deficiency and folate deficiency.