Macrocytic anemia causes: Difference between revisions
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==Overview== | ==Overview== | ||
'''Macrocytosis''' is the enlargement of [[red blood cell]]s with near-constant [[haemoglobin]] concentration, and is defined by a [[mean corpuscular volume]] (MCV) of greater than 100 femtolitres (the precise criterion varies between laboratories). | '''Macrocytosis''' is the enlargement of [[red blood cell]]s with near-constant [[haemoglobin]] concentration, and is defined by a [[mean corpuscular volume]] (MCV) of greater than 100 femtolitres (the precise criterion varies between laboratories). | ||
==Causes== | |||
Normal B12 absorption and action are dependent of 5 things: dietary intake, acid in the stomach, pancreatic secretions, secretion of IF by Gastric parietal cells, an ileum that can absorb the IF-B12 complex | |||
* Vitamin B12 Deficiency: <ref>Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:77 ISBN 1591032016</ref> <ref>Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:68 ISBN 140510368X</ref> | |||
#Deficient intake | |||
#Deficient intrinsic factor ([[pernicious anaemia]] or [[gastrectomy]]) | |||
#Bilogical competition for B12 by [[diverticulosis]], [[fistula]], intestinal [[anastomosis]], [[achlorhydria]] and infection by the marine parasite ''Diphyllobothrium latum'' | |||
#Selective B12 malabsorption (congenital and drug-induced) | |||
#Chronic [[pancreatitis]] | |||
#Ileal resection and bypass | |||
* Folate Deficiency: | |||
#Deficient intake. | |||
#Increased needs: [[pregnancy]], [[infant]], rapid cellular proliferation, and [[cirrhosis]] | |||
#Malabsorption (congenital and drug-induced) | |||
#Intestinal and jejunal resection | |||
* Combined Dieficiency (Tropical Sprue): Vitamin B12 & Folate. | |||
* Inherited [[DNA]] Synthesis Disorders: Deficient [[thiamine]] and factors (e.g. enzymes) responsible for folate metabolism. | |||
* Toxins and Drugs: | |||
#[[Folic acid]] antagonists ([[methotrexate]]) | |||
#[[Purine]] antagonists ([[6-mercaptopurine]]) | |||
#[[Pyrimidine]] antagonists (cytosine arabinoside) | |||
* [[Erythroleukemia]]. | |||
*In general: | |||
:* Nutritional defects (folic acid or vitamin B12 which is mainly from animal sources; [[vegan]]s may require supplementation) | |||
:* Chronic liver diseases | |||
:* Alcoholism | |||
:* Pregnancy | |||
:* Decreased production of [[intrinsic factor]] (this disease entity is called [[pernicious anemia]]) | |||
:* Intestinal [[malabsorption]] (due to an enteritis, [[celiac disease]] or other causes). | |||
:* Fish tapeworm infestation ([[Diphyllobothrium]] latum) | |||
:* Failure to replicate [[chromosomes]] due to lack of [[thymidine]]. | |||
:* [[Lesch-Nyhan Syndrome]] | |||
:* Cytotoxic drugs interfering with DNA synthesis | |||
:* [[Gut flora|intestinal flora]] disruption due to antibiotic use | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
Revision as of 14:35, 21 September 2012
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Macrocytosis is the enlargement of red blood cells with near-constant haemoglobin concentration, and is defined by a mean corpuscular volume (MCV) of greater than 100 femtolitres (the precise criterion varies between laboratories).
Causes
Normal B12 absorption and action are dependent of 5 things: dietary intake, acid in the stomach, pancreatic secretions, secretion of IF by Gastric parietal cells, an ileum that can absorb the IF-B12 complex
- Deficient intake
- Deficient intrinsic factor (pernicious anaemia or gastrectomy)
- Bilogical competition for B12 by diverticulosis, fistula, intestinal anastomosis, achlorhydria and infection by the marine parasite Diphyllobothrium latum
- Selective B12 malabsorption (congenital and drug-induced)
- Chronic pancreatitis
- Ileal resection and bypass
- Folate Deficiency:
- Deficient intake.
- Increased needs: pregnancy, infant, rapid cellular proliferation, and cirrhosis
- Malabsorption (congenital and drug-induced)
- Intestinal and jejunal resection
- Combined Dieficiency (Tropical Sprue): Vitamin B12 & Folate.
- Inherited DNA Synthesis Disorders: Deficient thiamine and factors (e.g. enzymes) responsible for folate metabolism.
- Toxins and Drugs:
- Folic acid antagonists (methotrexate)
- Purine antagonists (6-mercaptopurine)
- Pyrimidine antagonists (cytosine arabinoside)
- In general:
- Nutritional defects (folic acid or vitamin B12 which is mainly from animal sources; vegans may require supplementation)
- Chronic liver diseases
- Alcoholism
- Pregnancy
- Decreased production of intrinsic factor (this disease entity is called pernicious anemia)
- Intestinal malabsorption (due to an enteritis, celiac disease or other causes).
- Fish tapeworm infestation (Diphyllobothrium latum)
- Failure to replicate chromosomes due to lack of thymidine.
- Lesch-Nyhan Syndrome
- Cytotoxic drugs interfering with DNA synthesis
- intestinal flora disruption due to antibiotic use
References
gl:Anemia megaloblástica he:אנמיה מגלובלסטית it:Anemia megaloblastica sl:Megaloblastna anemija sr:Мегалобластна анемија