Megaloblastic Anemia
last authored:
last reviewed:
Introduction
This topic deals primarily with anemia caused by deficiency of folate or vitamin B12. While there are many causes of deficiency,
Pernicious anemia is an autoimmune condition
The Case of...
Causes and Risk Factors
Pernicious anemia is most common in elderly females.
Other risk factors include:
- malnutrition
- infancy
- pregnancy
B12 deficiency may be caused by the following:
- diet, ie strict vegan, with insufficient intake
- gastric atrophy
- post-gastrectomy
- inflammatory bowel disease
Folate deficiency is more common, as the body's stores are somewhat less. Deficiencies may be caused by the following:
- diet: insufficient intake
- infancy
- poverty
- alcoholism
- malabsorption
- anticonvulsants
- antimetabolites (eg methotrexate)
- increased demand (ie pregnancy)
Pathophysiology
In pernicious anemia, autoimmune antibodies are formed against the stomach's parietal cells. This leads to decreased acid production and a lack of intrinsic factor production, required for B12 absorption in the terminal ileum.
Deficiency of B12 and folate leads to decreased DNA synthesis.
Vitamin B12 is a cofactor for a cytoplasmic enzyme designed to transfer a methyl group. Demethylated tetrahydrofolate is required for production of DTTP.
As the cells themselves may be made, without a nucleus being produced, cells, develop a large mature cytoplasm with immature nuclei.
Signs and Symptoms
- history
- physical exam
History
Patients may often present with severe anemia, causing:
- fatigue
- shortness of breath
- palpitations
Mild jaundice may develop, secondary to hemolysis.
Glossitis and angular stomatitis may occur
B12 deficiency can also cause neurological conditions, such as:
- delirium, confusion
- dementia
- peripheral neuropathy
Physical Exam
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Diagnostic Imaging
Differential Diagnosis
Treatments
Folate and B12 are often given together. Folate alone should not be given, as it may mask B12 deficiency.
B12 may be given orally or by IM injection.
Folic acid is given orally.
Consequences and Course
Folate deficiency prior to, and surrounding conception, can lead to neural tube defects in infants.
Resources and References
Kaferie J, Strzoda CE. Evaluation of macrocytosis. Am Fam Physician. 2009;79:203-208
Topic Development
authors:
reviewers:
 |