- Describe his peripheral blood smear findings.
His peripheral blood smear shows red blood cells displaying macro-ovalocytosis and neutrophils with hypersegmentation.
- What is the diagnosis from these findings?
This is a macrocytic (megaloblastic) anemia. The neurologic findings suggest vitamin B12 deficiency (pernicious anemia).
- Which of the following tests would be most useful to determine the
etiology for these findings?
- A. Hemoglobin electrophoresis
- B. Reticulocyte count
- C. Stool for occult blood
- D. Vitamin B12 assay
- E. Bone marrow biopsy
Answer: D Macrocytic anemia could also be caused by a folate deficiency, but the neurologic findings would not be present.
- How do you explain his neurologic findings?
The B12 deficiency leads to a subacute combined degeneration of the spinal cord (posterior and lateral columns).
- How do treat his condition?
Most diets contain sufficient cobalamin, which is stored in the liver to provide a buffer against short-term dietary deficiencies. Lacto-ovo-vegetarian diets have minimal cobalamin. Cobalamin is released from food such as meat products by the action of acid and pepsin in the stomach, and this process is less efficient in the elderly. Gastric diseases such as atrophic gastritis, or gastrectomy, reduce or eliminate the parietal cells that produce intrinsic factor required for B12 binding and absorbtion. Intestinal abnormalities, particularly those involving the ileum where the B12 complexed with intrinsic factor is absorbed, may lead to deficiency.
Persons with chronic problems absorbing B12 can be given parenteral therapy in the form of intramuscular cyanocobalamin, typically 1000 micrograms of cobalamin per week for 2 months and then 1000 micrograms of cyanocobalamin intramuscularly every month thereafter. Persons who can still absorb cobalamin can be treated for deficiency with oral replacement therapy consisting of 2 mg of crystalline B12 per day.
Folic acid is mainly found in vegetable products, and it is not stored, so deficiencies come from poor diets. Many food products, such as cereals, contain folate supplementation. Folate deficiency may also be caused by malabsorbtion. There can be a relative lack of folate when there is increase erythropoiesis.
Folate deficiency is treated with an oral dose of 1 mg per day. Malabsorbtion may require higher doses of up to 5 mg per day.
Drugs that inhibit DNA synthesis (some chemotherapeutic agents such as hydroxyurea or 5-fluorouracil) and drugs that are folate antagonists such as methotrextate can produce megaloblastic anemia.
