Megaloblastic (Pernicious) Anemia

What is megaloblastic anemia?

Megaloblastic anemia is a type of anemia characterized by very large red blood cells. In addition to the cells being large, the inner contents of each cell are not completely developed. This malformation causes the bone marrow to produce fewer cells, and sometimes the cells die earlier than the 120-day life expectancy. Instead of being round or disk-shaped, the red blood cells can be oval.

What causes megaloblastic anemia?

Megaloblastic anemia is more common in individuals of northern European descent. While there are several types of megaloblastic anemia, the condition is caused by one of the following:

Folate (a type of B vitamin) deficiency
Vitamin B 12 deficiency caused by a lack of intrinsic factor in gastric (stomach) secretions--intrinsic factor is necessary for absorption of vitamin B 12
Vitamin B 12 deficiency caused by surgery that removes or bypasses the end of the small intestine where vitamin B 12 is absorbed

The type of anemia in which a lack of intrinsic factor occurs is called pernicious anemia. The inability to make intrinsic factor may be the result of several factors, such as chronic gastritis, gastrectomy (removal of all or part of the stomach), or an autoimmune condition (the body attacks its own tissues). Other types of megaloblastic anemia may be associated with type 1 diabetes, thyroid disease, and a family history of the disease.

What are the symptoms of megaloblastic anemia?

The following are the most common symptoms for megaloblastic anemia. However, each individual may experience symptoms differently. Symptoms may include:

Weak muscles
Numbness or tingling in hands and feet
Difficulty walking
Nausea
Decreased appetite
Weight loss
Irritability
Lack of energy or tiring easily (fatigue)
Diarrhea
Smooth and tender tongue
Increased heart rate (tachycardia)

The symptoms of megaloblastic anemia may resemble other blood conditions or medical problems. Always consult your doctor for a diagnosis.

How is megaloblastic anemia diagnosed?

Megaloblastic anemia is usually discovered during a medical examination through a routine blood test. In addition to a complete medical history and physical examination, diagnostic procedures for megaloblastic anemia may include additional blood tests and other evaluation procedures, including the Schilling test.

The Schilling test is performed to detect vitamin B 12 absorption. In the Schilling test, vitamin B 12 levels are measured in the urine after the ingestion of radioactive vitamin B 12. With normal absorption, the ileum (portion of the small intestine) absorbs more vitamin B 12 than the body needs and excretes the excess into the urine. With impaired absorption, however, little or no vitamin B 12 is excreted into the urine. When impaired absorption is the result, a second Schilling test can be performed with ingestion of intrinsic factor with the radioactive B 12 to determine if the problem is due to intrinsic factor production or absorption at the ileum.