Pernicious anemia is a decrease in the number of red blood cells because of inadequate absorption of vitamin B12 from the gastrointestinal tract. Vitamin B12 is necessary for red blood cell development. The deficiency of the vitamin causes the red blood cells to become abnormally large; hence, a more general term for the condition is megaloblastic anemia.
The parietal cells of the stomach release intrinsic factor, a protein, and it binds to vitamin B12 after hydrochloric acid in the stomach separates it from the food protein to which it attaches. This complex facilitates the absorption of the vitamin through the ileum of the small intestine.
Risk factors
The disease tends to occur in elderly people who are at least 60 years old; however, it may become apparent as early as age 30. Previously scientists have believed that this disease occurred primarily in elderly Caucasians, but there is evidence that African-Americans also have it in significant proportions. The distribution of pernicious anemia among other demographic variables, such as gender, is not well known.
It particularly affects people of Scandinavian or Northern European descent. Other risk factors include history of autoimmune disorders and family history of pernicious anemia. Elderly people are at risk for this condition because they tend to develop malabsorption problems from atrophic gastritis and therefore are prone to malnutrition. Moreover, elderly individuals may have cognitive dysfunction, financial difficulties, social isolation, and mobility limitation, and this will place them at risk for inadequate dietary intake.
People who have undergone intestinal or stomach surgery may be at risk for vitamin B12 deficiency. Strict vegetarians will be at risk because their diet does not include any form of animal protein. Unless plant foods are fortified, they do not contain any vitamin B12. If vegetarians add eggs, milk, and other dairy products, they can receive adequate amounts of the vitamin. Otherwise, supplementation of the nutrient from a physician is necessary.
Other good sources of vitamin B12 are fortified cereals, shellfish, poultry, beef liver, clams, and meat.
Several other medical conditions may contribute to the occurrence of vitamin B12 deficiency. These include human immunodeficiency virus infection, celiac sprue, Crohn disease, and bacterial overgrowth in the small intestine. For several decades, the medical literature has documented the relationship between vitamin B12 deficiency and infestation with fish tapeworm or Diphyllobothrium latum. All of these medical conditions interfere with the intestinal absorption of the vitamin.
Malabsorption will occur in atrophic gastritis which is inflammation of the stomach wall. There may also be an autoimmune process as well in patients with pernicious anemia in which the individual’s immune system attacks the parietal cells of the stomach, or even intrinsic factor may be a target. Patients with pernicious anemia may develop gastric polyps, and they are at risk for stomach cancer.
In rare instances, a person will have an inability to produce sufficient intrinsic factor at birth. This is a hereditary condition which the baby will acquire from both parents and accounts for the presence of pernicious anemia.
Pregnant women have additional needs for vitamin B12, and if they breastfeed the baby, it is essential that both mother and child receive an adequate supply of it. Breastfeeding mothers who follow strict vegetarian diets may not be able to furnish sufficient amounts of vitamin B12 unless they take a supplement from their physician.
If the baby does not obtain enough of the vitamin during breastfeeding or any other time, he or she may experience failure to thrive, developmental delays, anemia, weakness, balance difficulties, and decrease in muscle tone. Neural tube defects may also occur if the fetus does not get adequate amounts of vitamin B12 during pregnancy.
Prevention and treatment
There is no way to prevent pernicious anemia, but if the physician detects pernicious anemia in its early stages, treatment of it with injections of vitamin B12 for the remainder of the patient’s lifetime is usually successful. The other requirement is the patient must follow a well-balanced diet.
References
National Institutes of Health. Medline Plus. (2008). Pernicious anemia. Retrieved January 25,
2011.
National Institutes of Health. Office of Dietary Supplements. (2010). Vitamin B12. Retrieved
January 25, 2011.
Michael Koger - Dr. Koger obtained his medical education at Meharry Medical College and specialized in Internal Medicine.
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