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Blood Film

Megaloblastic Blood Film Findings

February 15th, 2021


Megaloblastic anaemia is a condition where the bone marrow produces large immature red blood cells called megaloblasts which go on to become large, ineffective red blood cells.
  • Blood Film Findings in Megaloblastic Anaemia

  • Macrocytic hyperchromic anaemia (may be normocytic in early disease)
  • Anisocytosis: variation in size of red blood cells
  • Macroovalocytes: large, round cells
  • Teardrop cells
  • Hypersegmented neutrophils (5 or more nuclear lobes)
  • A hypersegmented neutrophil in a patient with megaloblastic anaemia:
  • A hypersegmented neutrophil in a patient with megaloblastic anaemia
  • Causes of Megaloblastic Anaemia

  • Haematinic Deficiency

  • B12 deficiency - pernicious anaemia, H pylori gastritis, malabsorption, resection of the stomach or terminal ileum, chronic pancreatitis
  • Folate deficiency - nutritional deficiency, alcohol abuse, malabsorption, pregnancy, folate antagonists
  • Drugs

  • Folate antagonists - methotrexate, trimethoprim
  • Purine analogues - azathioprine, 6-mercaptopurine, allopurinol, cladribine, fludarabine
  • Pyramidine antagonists - 5-fluorouracil, cytarabine, gemcitabine, capecitabine
  • Anticonvulsants - valproate, phenytoin
  • Reverse transcriptase inhibitors - abacavir, emtricitabine, entecavir, lamivudice, zidovudine, tenofovir, efavirenz
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