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From Wikipedia, the free encyclopedia
Other namesMacrocytes
SymptomsShortness of breath, weakness, heart murmur, tachycardia
CausesVitamin B12 deficiency, Folic acid deficiency, Malabsorption, Alcoholism
Risk factorsBone marrow failure, hematologic malignancy
Diagnostic methodSymptoms, Complete blood count, Peripheral blood smear, Vitamin B12 level, Red cell folate level

Macrocytosis is a condition where red blood cells are larger than normal.[1] These enlarged cells, also known as macrocytes, are defined by a mean corpuscular volume (MCV) that exceeds the upper reference range established by the laboratory and hematology analyzer (usually >110 fL).[2] Upon examination of a peripheral blood smear under microscope, these macrocytes appear larger than standard erythrocytes. It’s noteworthy that macrocytosis is a common morphological feature in neonatal peripheral blood.[3] The presence of macrocytosis can indicate a range of conditions, from benign, treatable illnesses to more serious underlying disorders.



Macrocytes may be oval or round. Oval macrocytes (also called megalocytes)[4] are seen in conditions associated with dyserythropoiesis including megalobalstic anemia, myelodysplstic syndromes, Fanconi anemia and CDA type I & III. Round macrocytes are associated with other causes of macrocytosis.



In humans, the most prevalent causes of macrocytosis are often linked to alcoholism and deficiencies in vitamin B12 or folic acid (Vitamin B9), or a combination of these factors.[5] These conditions can affect the production and development of red blood cells, leading to their enlargement. Another cause of macrocytosis is benign familial macrocytosis, which is a hereditary condition that doesn’t present any symptoms.[6] Despite the larger size of the red blood cells, individuals with this condition typically have normal red blood cell function. It’s always important to consult with a healthcare professional for accurate diagnosis and treatment. Causes of Macrocytosis may include:



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

See also



  1. ^ Kaferle, Joyce; Strzoda, Cheryl E. (2009-02-01). "Evaluation of macrocytosis". American Family Physician. 79 (3): 203–208. ISSN 0002-838X. PMID 19202968.
  2. ^ Woodruff, James N.; Blanchard, Anita K. (2016-06-11). Primary Care of Adult Women, An Issue of Obstetrics and Gynecology Clinics of North America. Elsevier Health Sciences. ISBN 978-0-323-44623-5.
  3. ^ Bain, Barbara J. (2015-01-20). Blood Cells: A Practical Guide. John Wiley & Sons. ISBN 978-1-118-81733-9.
  4. ^ Anderson, Shauna Christine; Poulsen, Keila (2003). Atlas of Hematology. Lippincott Williams & Wilkins. ISBN 978-0-7817-2662-7.
  5. ^ Pacholok, Sally; Stuart, Jeffrey J. (2011-01-01). Could It Be B12?: An Epidemic of Misdiagnoses. Linden Publishing. ISBN 978-1-61035-065-5.
  6. ^ "Macrocytosis: Practice Essentials, Pathophysiology, Etiology". 2022-10-07. {{cite journal}}: Cite journal requires |journal= (help)