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Macrocytosis (possible causes of an macrocytosis (MCV >100fl) )

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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In almost all of these cases the condition causes macrocytosis by inhibiting cell division of the red cell precursors in the bone marrow

  • less cell division gives rise to larger red cells

Causes include:

  • Alcohol and/or liver disease (esp. if macrocytosis accompanied by thrombocytopenia but no or only mild anaemia)

  • Vitamin B12/folate deficiency

  • Pregnancy and newborn

  • Hypothyroidism

  • Haemolytic anaemia (where macrocytosis results from the presence of increased numbers of reticulocytes, which are larger than mature red cells, in the blood)

  • Myelodysplasia

  • Drugs esp anti-metabolites that interfere with DNA synthesis and cell division e.g.
    • Hydroxycarbamide
    • Azathioprine
    • Methotrexate
    • Trimethoprim
    • Zidovudine (AZT) and other nucleoside reverse transcriptase inhibitor treatments for HIV

  • Aplastic anaemia or other causes of 'bone marrow stress'

  • Acquired sideroblastic anaemia (very rare)

Reference:

  • 1) Royal United Hospital Bath NHS Trust. Guidelines for the Investigation & Management of vitamin B12 deficiency (Accessed February 9th 2014)

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