Macrocytic Anemia Causes

Anemia is a common medical condition that is characterized by low levels of hemoglobin. There are different types of anemia, and these vary according to the underlying causes, but ultimately, the problem comes down to the resulting lack in hemoglobin. Hemoglobin is a molecule that binds and releases oxygen from the blood to the tissues.

One of the most common types of anemia is macrocytic anemia, which is characterized by having red blood cells that are larger than normal. Causes of macrocytic anemia are numerous, so this subject merits some discussion for better understanding.

Macrocytic Anemia Causes

Macrocytic anemias can be classified further into two main groups. First, you have the megaloblastic macrocytic anemia, which is the more common type. Then you have the non-megaloblastic macrocytic anemia, which is usually associated with various serious medical problems, such as liver or bone marrow disease. In some cases, no causes can be identified with the non-megaloblastic type of anemia.

Megaloblastic Macrocytic Anemia Causes

  • DNA production disrupted

The bone marrow manufactures immature red blood cells (blasts) before they are released into the bloodstream. If the immature red blood cells have genetic material or DNA malfunction, the cells enlarge before they leave the bone marrow and remain enlarged as they enter the circulation. These enlarged, immature red blood cells (called megaloblasts) arise due to defective DNA production. Factors that cause disruption in DNA production in red blood cells also affect other types of cells (such as the white blood cells) in the bone marrow. So, viewed through a microscope, both red and white cells in megaloblastic anemia appear abnormal.

  • Medications

One of thecommon macrocytic anemia causes is medication, especially those that interfere with folate metabolism and absorption. These include methotrexate, a drug used to treat cancer and rheumatoid arthritis, anticonvulsants, anti-cancer drugs, HIV medications, antidiabetic drugs (metformin) and antimicrobials.

  • Vitamin B12 deficiency

Vitamin B12 deficiency takes years to develop because of the large stores of the substance in the liver. Causes may include autoimmune Addisonian pernicious anemia, complication of surgery such as ileocolic resection or gastrectomy, HIV infection, bacterial overgrowth, parasitic infestation, dietary deficiency, and pernicious anemia which is a condition common in the elderly.

  • Folate deficiency

Folate deficiency may be due to dietary deficits, malabsorption, hemolysis, leukemia, some skin diseases, pregnancy, increased urinary excretion of folate related to acute hepatitis, heart failure, and dialysis.

Drugs causing folate deficiency include anticonvulsants, alcohol, methotrexate, trimethoprim and sulfasalazine.

Non-Megaloblastic Macrocytic Anemia Causes

Causes of non-megaloblastic macrocytic anemia are not related to defective DNA synthesis. Non-megaloblastic macrocytic anemia is less common and is characterized by the absence of megaloblasts, and instead, the presence of mature but large red blood cells. This type of red blood cells is normally seen in newborns only. Causes include:

  • Chronic alcoholism
  • Liver disease
  • Hypothyroidism
  • Reticulocytosis
  • Blood disorders like red-cell aplasia, aplastic anemia, myelodysplastic syndromes, and myeloid leukemia
  • Drugs such as azathioprine
  • Pregnancy

Management of Macrocytic Anemia

Treatments depend on the macrocytic anemia causes and type of anemia involved. Proper evaluation and diagnosis are necessary and this may be done with the aid of a test called peripheral blood smear.

Diagnosing Macrocytic Anemia

A blood smear is examined under the microscope to see the size, shape and number of the red blood cells. Megaloblastic macrocytic anemia is characterized by the presence of Howell-Jolly bodies that appear assmall specks inside the red blood cells. These indicate that these are immature red blood cells that have been released from the bone marrow into the blood stream to compensate for anemia. Patients may also need to be evaluated for vitamin deficiencies.

In patients who have non-megaloblastic macrocytic anemia, liver and bone marrow function need to be checked.

Treatments for Megaloblastic Macrocytic Anemia

The treatment of megaloblastic anemia depends on the specific cause, as well as other factors like your age, overall health, severity of disease, and your response to treatment. These treatments are usually continued for long periods.

If it's caused by B-12 vitamin deficiency:

Megaloblastic anemia related to vitamin B-12 deficiency is treated with injections of the vitamin on a monthly base. You may also be advised to take oral supplements and eat more foods that are rich in vitamin B-12 such as:

  • fortified cereals
  • milk
  • eggs
  • chicken
  • red meats
  • shellfish

If it's caused by folate deficiency:

Megaloblastic anemia related to folate deficiency may be treated with intravenous or oral folic acid supplements. You may also be advised to adopt dietary changes to boost your folate levels. Foods that are rich in folate include:

  • leafy green vegetables
  • oranges
  • enriched grains
  • peanuts
  • lentils

Treatments for Non-Megaloblastic Macrocytic Anemia

Treatment for non-megaloblastic macrocytic anemia is more difficult because it is usually caused by chronic disorders like liver or bone marrow disease. Therefore, management is primarily directed at treating the underlying disorder, which is usually serious. Proper diagnosis must be done prior to treatment and management could be more complicated due to the nature of the disease.

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