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Blood Film

Megaloblastic Blood Film Findings



  • 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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 Adewoyin AS. Peripheral blood film-a review. Annals of Ibadan postgraduate medicine. 2014;12(2):71-9.
Antwi-Baffour S, Quao E, Kyeremeh R, Mahmood SA. Prolong storage of blood in EDTA has an effect on the morphology and osmotic fragility of erythrocytes. Int J Biomed Sci Eng. 2013;1(2):20-3.
 Bacon PA, Sewell RL, Crowther D. Reactive lymphoid cells ('Immunoblasts') in autoimmune and haematological disorders. Clinical and experimental immunology. 1975 Feb;19(2):201.
Bennett JM, Healey PJ. Spherocytic hemolytic anemia and acute cholecystitis caused by Clostridium welchii. New England Journal of Medicine. 1963 May 9;268(19):1070-2.
Brigden ML. Detection, education and management of the asplenic or hyposplenic patient. American family physician. 2001 Feb 1;63(3):499.
Gütgemann I, Heimpel H, Nebe CT. Significance of teardrop cells in peripheral blood smears. LaboratoriumsMedizin. 2013 Sep 1;37(5).
 Kobayashi SD, DeLeo FR. Role of neutrophils in innate immunity: a systems biology?level approach. Wiley Interdisciplinary Reviews: Systems Biology and Medicine. 2009 Nov 1;1(3):309-33.
Lawrence C, Atac BU. Hematologic changes in massive burn injury. Critical care medicine. 1992 Sep;20(9):1284-8.
 Mhawech P, Saleem A. Inherited giant platelet disorders: classification and literature review. American journal of clinical pathology. 2000 Feb 1;113(2):176-90.
Owen JS, Brown DJ, Harry DS, McIntyre N, Beaven GH, Isenberg H, Gratzer WB. Erythrocyte echinocytosis in liver disease. Role of abnormal plasma high density lipoproteins. The Journal of clinical investigation. 1985 Dec 1;76(6):2275-85.
Perrotta S, Gallagher PG, Mohandas N. Hereditary spherocytosis. The Lancet. 2008 Oct 18;372(9647):1411-26.
Shen SC, Ham TH, Fleming EM. Studies on the destruction of red blood cells: mechanism and complications of hemoglobinuria in patients with thermal burns: spherocytosis and increased osmotic fragility of red blood cells. New England Journal of Medicine. 1943 Nov 4;229(19):701-13.
 Van de Vyver A, Delport EF, Esterhuizen M, Pool R. The correlation between C-reactive protein and toxic granulation of neutrophils in the peripheral blood. SAMJ: South African Medical Journal. 2010 Jul;100(7):0-.
William BM, Corazza GR. Hyposplenism: a comprehensive review. Part I: basic concepts and causes. Hematology. 2007 Feb 1;12(1):1-3.