1. Macrocytic Anemias
Blake Briggs, Class of 2017

2. Breakdown of Macrocytic anemia (MCV >100)
Macrocytic nonmegaloblastic: RBC size increases due to increased cytoplasmic contents or immaturity.
Chronic alcoholism (cholesterol accumulates in RBC)
Hypothyroidism
Reticulocytosis
Macrocytic megaloblastic: defect in DNA production in RBC precursors.
Folate or B12 deficiency
Folate antagonists (Methotrexate, certain immunosuppressants, HIV meds)

3. Macrocytic Megaloblastic Anemia
Less DNA production  larger precursors released from marrow
Peripheral smear for all megaloblastic anemias: RBC’s that are either equal in size to or larger than lymphocyte nuclei. There is also hypersegmented neutrophils, which are a common finding on board exam smears.

4. Smear for megaloblastic anemia

5. Relevant biochemistry

6. B12 Deficiency
B12, also called Cobalamin, is found in red meats. Absorbed in terminal ileum. Body stores last for years.
Absorbed with Intrinsic factor, which is made by parietal cells in the stomach. Intrinsic factor is necessary for B12 absorption.
Causes of low B12
Pernicious anemia: autoimmune disease against parietal cells.
Anything that causes decreased absorbed in the terminal ileum (i.e. Crohn’s disease, short gut syndrome
Malnutrition: classically in developed countries this is due to alcoholism.
Veganism? Rare and disputed, but could be a risk factor on board questions.

7. B12 deficiency Symptoms:
Glossitis
Subacute Combined Neurodegeneration: peripheral neuropathy- loss of dorsal columns (sensory) and corticospinal (motor) tracts; dementia/confusion/ataxia.
Treatment: B12 injections. Nerve damage can be permanent.

8. Folate Deficiency
Folate is found in greens and whole grains. Absorbed in proximal jejunum. Body stores last a few months.
Causes of low folate:
Malnutrition: in developed countries, alcoholics or those on certain diets.
Folate antagonist medications: Methotrexate, Trimethoprim, Pyrimethamine
Symptoms: None! Only if the patient is pregnant  neural tube defects in the fetus.
Treatment: Folate administration. Neural tube defects irreversible.

9. Thanks for listening
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