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Macrocytosis: What causes it?

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Drugs & Diseases
Macrocytosis Q&A

What is macrocytosis?

Updated: Nov 18, 2017
  • Author: Vincent E Herrin, MD, FACP; Chief Editor: Emmanuel C Besa, MD  more…
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Macrocytosis is a term used to describe erythrocytes that are larger than normal, typically reported as mean cell volume (MCV) greater than 100 fL. The amount of hemoglobin increases proportionately with the increase in cell size. Therefore, if the increase in MCV is not related to macrocytic anemia, the mean cell hemoglobin concentration (MCHC) also increases in proportion. Increased MCV is an indication of macrocytic anemia when any of the following is present
[ 1 ]

  • In nonpregnant females, hemoglobin

  • In pregnant females, hemoglobin

  • In males, hemoglobin </ul>

Source Article: Macrocytosis: Practice Essentials

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  1. Moore CA, Adil A. Anemia, Macrocytic. 2017 Jun. [Medline] . [Full Text] .

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  10. Grgic I, Kaistha BP, Paschen S, Kaistha A, Busch C, Si H, et al. Disruption of the Gardos channel (KCa3.1) in mice causes subtle erythrocyte macrocytosis and progressive splenomegaly. Pflugers Arch. 2009 Jun. 458(2):291-302. [Medline] .

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  12. Schallier D, Trullemans F, Fontaine C, Decoster L, De Greve J. Tyrosine kinase inhibitor-induced macrocytosis. Anticancer Res. 2009 Dec. 29 (12):5225-8. [Medline] .

  13. Kloth JS, Hamberg P, Mendelaar PA, Dulfer RR, van der Holt B, Eechoute K, et al. Macrocytosis as a potential parameter associated with survival after tyrosine kinase inhibitor treatment. Eur J Cancer. 2016 Mar. 56:101-6. [Medline] .

  14. Sechi LA, De Carli S, Catena C, Zingaro L, Bartoli E. Benign familial macrocytosis. Clin Lab Haematol. 1996 Mar. 18(1):41-3. [Medline] .

  15. Bessman JD, Banks D. Spurious macrocytosis, a common clue to erythrocyte cold agglutinins. Am J Clin Pathol. 1980 Dec. 74(6):797-800. [Medline] .

  16. Field EA, Speechley JA, Rugman FR, Varga E, Tyldesley WR. Oral signs and symptoms in patients with undiagnosed vitamin B12 deficiency. J Oral Pathol Med. 1995 Nov. 24(10):468-70. [Medline] .

  17. Ellaway C, Christodoulou J, Kamath R, Carpenter K, Wilcken B. The association of protein-losing enteropathy with cobalamin C defect. J Inherit Metab Dis. 1998 Feb. 21(1):17-22. [Medline] .

  18. Fernando OV, Grimsley EW. Prevalence of folate deficiency and macrocytosis in patients with and without alcohol-related illness. South Med J. 1998 Aug. 91(8):721-5. [Medline] .

  19. Curtis D, Sparrow R, Brennan L, Van der Weyden MB. Elevated serum homocysteine as a predictor for vitamin B12 or folate deficiency. Eur J Haematol. 1994 Apr. 52(4):227-32. [Medline] .

  20. Lindenbaum J, Savage DG, Stabler SP, Allen RH. Diagnosis of cobalamin deficiency: II. Relative sensitivities of serum cobalamin, methylmalonic acid, and total homocysteine concentrations. Am J Hematol. 1990 Jun. 34(2):99-107. [Medline] .

  21. Phekoo K, Williams Y, Schey SA, Andrews VE, Dudley JM, Hoffbrand AV. Folate assays: serum or red cell?. J R Coll Physicians Lond. 1997 May-Jun. 31(3):291-5. [Medline] .

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  23. Ganji V, Kafai MR. Hemoglobin and hematocrit values are higher and prevalence of anemia is lower in the post-folic acid fortification period than in the pre-folic acid fortification period in US adults. Am J Clin Nutr. 2009 Jan. 89(1):363-71. [Medline] .

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      Contributor Information and Disclosures


      Vincent E Herrin, MD, FACP Professor of Medicine, Division of Hematology and Medical Oncology, Director, Medicine Residency Program, University of Mississippi School of Medicine

      Vincent E Herrin, MD, FACP is a member of the following medical societies: American College of Physicians , American College of Physicians-American Society of Internal Medicine , American Society of Clinical Oncology , Southern Society for Clinical Investigation , American Society of Hematology

      Disclosure: Nothing to disclose.

      Chief Editor

      Emmanuel C Besa, MD Professor Emeritus, Department of Medicine, Division of Hematologic Malignancies and Hematopoietic Stem Cell Transplantation, Kimmel Cancer Center, Jefferson Medical College of Thomas Jefferson University

      Emmanuel C Besa, MD is a member of the following medical societies: American Association for Cancer Education , American Society of Clinical Oncology , American College of Clinical Pharmacology , American Federation for Medical Research , American Society of Hematology , New York Academy of Sciences

      Disclosure: Nothing to disclose.


      Russell Burgess, MD (Retired) Chief, Division of Hematology/Oncology, Eastern Carolina Internal Medicine, PA

      Russell Burgess, MD is a member of the following medical societies: American College of Physicians and American Medical Association

      Disclosure: Nothing to disclose.

      Ronald A Sacher, MB, BCh, MD, FRCPC Professor, Internal Medicine and Pathology, Director, Hoxworth Blood Center, University of Cincinnati Academic Health Center

      Ronald A Sacher, MB, BCh, MD, FRCPC is a member of the following medical societies: American Association for the Advancement of Science , American Association of Blood Banks , American Clinical and Climatological Association , American Society for Clinical Pathology , American Society of Hematology , College of American Pathologists , International Society of Blood Transfusion, International Society on Thrombosis and Haemostasis , and Royal College of Physicians and Surgeons of Canada

      Disclosure: Glaxo Smith Kline Honoraria Speaking and teaching; Talecris Honoraria Board membership

      Paul Schick, MD Emeritus Professor, Department of Internal Medicine, Thomas Jefferson University Medical College; Research Professor, Department of Internal Medicine, Drexel University College of Medicine; Adjunct Professor of Medicine, Lankenau Hospital, Wynnewood, PA

      Paul Schick, MD is a member of the following medical societies: American College of Physicians , American Heart Association , American Society of Hematology , International Society on Thrombosis and Haemostasis , and New York Academy of Sciences

      Disclosure: Nothing to disclose.

      Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

      Disclosure: Medscape Reference Salary Employment

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      From Wikipedia, the free encyclopedia

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      For the kelp genus, see Macrocystis .
      Classification and external resources
      Specialty hematology
      ICD – 10 D75.8
      ICD – 9-CM 289.89
      DiseasesDB 7688
      eMedicine med/1381
      [ edit on Wikidata ]

      Macrocytosis is the enlargement of red blood cells with near-constant hemoglobin concentration, and is defined by a mean corpuscular volume (MCV) of greater than 100 femtolitres (the precise criterion varies between laboratories). The enlarged erythrocytes are called macrocytes or megalocytes (both words have roots meaning “big cell”).


      • 1 Causes
      • 2 Complications
      • 3 See also
      • 4 References

      Causes[ edit ]

      Most commonly (especially when the increase in size is mild, and just above normal range) the cause is bone marrow dysplasia secondary to alcohol abuse and chronic alcoholism .

      Poor absorption of vitamin B12 in the digestive tract can also cause macrocytosis.

      Gastrointestinal diseases that may cause macrocytosis include celiac disease (severe sensitivity to gluten from wheat and other grains that causes intestinal damage) and Crohn’s disease (inflammatory bowel disease that can affect any part of the gastrointestinal tract). (Source

      Other causes may include:

      • megaloblastosis ( vitamin B12 or folate deficiency; or DNA synthesis-inhibiting drugs)
      • hypothyroidism
      • chronic obstructive airway disease
      • aplastic anemia
      • reticulocytosis (commonly from hemolysis or a recent history of blood loss ).
      • liver disease
      • myeloproliferative disease
      • myelodysplastic syndrome which most commonly presents with macrocytic anemia [1]
      • chronic exposure to benzene
      • pregnancy (most common, and requires no treatment as the person affected will return to normal post-partum)

      Complications[ edit ]

      No complications arise from macrocytosis itself and a prognosis will be determined from its cause.

      See also[ edit ]

      • Macrocytic anemia

      References[ edit ]

      1. ^ Greenberg, P. L., et al. “Myelodysplastic syndromes: clinical practice guidelines in oncology.” Journal of the National Comprehensive Cancer Network: JNCCN 11.7 (2013): 838-874.
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