University of Virginia Health System

Macro-ovalocyte
(oval macrocyte)

Peripheral blood smear, Wright-Giemsa stain, 1000x

Description:

The macrocyte is oval instead of round.

Pathobiology:

In most instances is due to megaloblastic erythropoiesis (Vitamin B-12 or folate deficiency) but may be seen with dyserythropoiesis (myelodysplastic syndromes).  

Differential diagnosis:

• Vitamin B-12 and folate deficiency of whatever cause. Although macro-ovalocytes are characteristic in these deficiency states, they are not pathognomonic. Anisopoikilocytosis is often present, particularly in more advanced cases. If associated with hypersegmented granulocytes in the absence of other causes (e.g. drugs), the findings are essentially diagnostic of Vitamin B-12 or folate deficiency. 
• Dyserythropoietic disorders, e.g. myelodysplastic syndromes

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