Macrocytosis
{{for|the kelp genus|Macrocystis}}
{{More citations needed|date=May 2021}}
{{Infobox medical condition (new)
| name = Macrocytosis
File:Red_Blood_Cells_according_to_sizes.png
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| field = Hematology
| synonyms = Macrocytes
| symptoms = Shortness of breath, weakness, heart murmur, tachycardia
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| causes = Vitamin B12 deficiency, Folic acid deficiency, Malabsorption, Alcoholism
| risks = Bone marrow failure, hematologic malignancy
| diagnosis = Symptoms, Complete blood count, Peripheral blood smear, Vitamin B12 level, Red cell folate level
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Macrocytosis is a condition where red blood cells are larger than normal.{{Cite journal |last1=Kaferle |first1=Joyce |last2=Strzoda |first2=Cheryl E. |date=2009-02-01 |title=Evaluation of macrocytosis |url=https://pubmed.ncbi.nlm.nih.gov/19202968/ |journal=American Family Physician |volume=79 |issue=3 |pages=203–208 |issn=0002-838X |pmid=19202968}} 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).{{Cite book |last1=Woodruff |first1=James N. |url=https://books.google.com/books?id=XUtgDAAAQBAJ&pg=PA248 |title=Primary Care of Adult Women, An Issue of Obstetrics and Gynecology Clinics of North America |last2=Blanchard |first2=Anita K. |date=2016-06-11 |publisher=Elsevier Health Sciences |isbn=978-0-323-44623-5 |language=en}} Upon examination of a peripheral blood smear under microscope, these macrocytes appear larger than standard erythrocytes. Macrocytosis is a common morphological feature in neonatal peripheral blood.{{Cite book |last=Bain |first=Barbara J. |url=https://books.google.com/books?id=dckoCQAAQBAJ&dq=macrocytes+in+neonates&pg=PA74 |title=Blood Cells: A Practical Guide |date=2015-01-20 |publisher=John Wiley & Sons |isbn=978-1-118-81733-9 |language=en}} The presence of macrocytosis can indicate a range of conditions, from benign, treatable illnesses to more serious underlying disorders.
Types
Macrocytes may be oval or round. Oval macrocytes (also called megalocytes){{Cite book |last1=Anderson |first1=Shauna Christine |url=https://books.google.com/books?id=pB_fyiPkksUC&dq=oval+macrocyte+megalocyte&pg=PA12 |title=Atlas of Hematology |last2=Poulsen |first2=Keila |date=2003 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-2662-7 |language=en}} are seen in conditions associated with dyserythropoiesis including megaloblastic anemia, myelodysplstic syndromes, Fanconi anemia and CDA type I & III. Round macrocytes are associated with other causes of macrocytosis.
Causes
In humans, the most prevalent causes of macrocytosis are often linked to alcoholism and deficiencies in vitamin B12 or folate (vitamin B{{ssub|9}}), or a combination of these factors.{{Cite book |last1=Pacholok |first1=Sally |url=https://books.google.com/books?id=I13L1WDTNeoC&q=vitamin+b12+and+folate+deficiency+are+common+causes+of+macrocytosis |title=Could It Be B12?: An Epidemic of Misdiagnoses |last2=Stuart |first2=Jeffrey J. |date=2011-01-01 |publisher=Linden Publishing |isbn=978-1-61035-065-5 |language=en}} 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 does not present symptoms.{{Cite journal |date=2022-10-07 |title=Macrocytosis: Practice Essentials, Pathophysiology, Etiology |url=https://emedicine.medscape.com/article/203858-overview}} Despite the larger size of the red blood cells, individuals with this condition typically have normal red blood cell function. Causes of macrocytosis may include:
- Megaloblastic anemia due to deficiency or abnormal metabolism of vitamin B{{ssub|12}} or folate
- Poor dietary intake, including due to strict veganism
- Increased requirements
- Pernicious anemia
- Malabsorption syndromes
- Alcoholism
- Smoking
- Reticulocytosis due to hemolysis, blood loss and hematinics
- Hypothyroidism
- Myelodysplastic syndromes (MDS)
- Congenital dyserythropoietic anemia
- Aplastic anemia and bone marrow failure syndromes
- Inherited disorders of DNA synthesis
- Homocystinuria
- Lesch–Nyhan syndrome
- Deficient enzymes for folate metabolism
- Liver disease
- Chronic obstructive pulmonary disorder (COPD)
- Certain drugs, including folate antagonists, purine antagonists, tyrosine kinase inhibitors, anti-HIV drugs etc.
Complications
Macrocytosis does not itself lead to complications. Prognosis depends on its cause.
See also
References
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External links
{{Medical resources
| DiseasesDB = 7688
| ICD10 = {{ICD10|D|75|8|d|70}}
| ICD9 = {{ICD9|289.89}}
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| eMedicineSubj = med
| eMedicineTopic = 1381
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{{Abnormal clinical and laboratory findings}}
{{Alcohol and health}}
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