Anemia (Pernicious)

Definition

Definition of Anemia (Pernicious)
Anemia is a condition in which the body does not have a sufficient number of red blood cells or hemoglobin. Hemoglobin is present within red blood cells and is important for carrying oxygen to all tissues of the body. In males, anemia is typically defined as hemoglobin level of less than 13.5 gram/100ml, while in women, a hemoglobin level of less than 12.0 gram/100ml is considered to be indicative of anemia. These definitions may vary slightly depending on the source and the laboratory reference used. Pernicious is a term that means destructive, injurious or deadly.

Pernicious anemia is a disease where large, immature, nucleated cells (megaloblasts, which are forerunners of red blood cells) circulate in the blood, and do not function as blood cells; it is a disease caused by impaired uptake of vitamin B-12 due to the lack of intrinsic factor (IF) in the gastric mucosa. It was termed "pernicious" because before it was learned that vitamin B-12 could treat the anemia, most people that developed the disease died from it.

Symptoms

Symptoms of Anemia (Pernicious)
Pernicious anemia presents insidiously, and many of the signs and symptoms are due to anemia itself, where anemia is present. However, in 20% of cases of cobalamin deficiency, anemia is not observed. While it may consist of the triad of paraesthesias, sore tongue and weakness, this is not the chief symptom complex. The patient may complain of fatigue, depression, forgetfulness, difficulty concentrating, low-grade fevers, nausea and gastrointestinal symptoms (heartburn), weight loss. Because PA may affect the spinal cord, the patient may also complain of impaired urination, loss of sensation in the feet, unsteady gait, weakness, and clumsiness. Anemia may cause tachycardia (rapid heartbeat) and cardiac murmurs, along with a waxy pallor. In severe cases, the anemia may cause evidence of congestive heart failure.

Causes

Causes of Anemia (Pernicious)
Pernicious anemia is considered to be an autoimmune disease, in which the body's own immune system mistakenly damages its own tissues. It is believed that the decreased absorption of vitamin B-12 from the gastrointestinal tract in pernicious anemia results from the presence of an autoantibody against intrinsic factor (IF), a protein made in the stomach that is necessary for the absorption of vitamin B-12. Normally, vitamin B-12 binds to intrinsic factor in the stomach, and this facilitates its absorption by the small intestine further along in the digestive process. Along with the autoimmune process that attacks the IF protein and lowers IF levels in stomach secretions, another autoimmune reaction against the stomach lining cells also occurs, resulting in a form of inflammation known as chronic atrophic gastritis.

Diagnosis

Diagnosis of Anemia (Pernicious)
The first step is always a thorough history and physical examination by a health care practitioner. The results of this examination are used to help direct further testing. A number of laboratory tests are available that can help diagnose pernicious anemia as well as other causes of vitamin B-12 deficiency. These tests include:

1. A complete blood cell count (CBC)
2. Examination of a blood smear (peripheral smear) under a microscope, often performed in association with a CBC
3. Blood vitamin B-12 level measurements
4. Tests for the presence of autoantibodies to intrinsic factor or stomach lining cells
5. Blood levels of iron and iron-binding capacity
6. Folate levels (which are often reduced when vitamin B-12 levels are low)
7. Blood levels of methylmalonic acid or homocysteine, both of which may be sensitive indicators of vitamin B-12 deficiency
8. The Schilling test, a measure of how well the body can absorb vitamin B-12, is less commonly used today than in the past.
9. Finally, bone marrow aspiration or bone marrow biopsy may be recommended in some cases if bone marrow disorders are suspected

Treatment

Treatment of Anemia (Pernicious)
The symptoms of pernicious anemia and vitamin B-12 deficiency can be treated by replenishing the vitamin B-12 supply in the body. If a condition other than pernicious anemia is responsible for vitamin B-12 deficiency, treatment must also be directed at the underlying condition. Symptoms of vitamin B-12 deficiency may be improved after just a few days of medical treatment.

Vitamin B-12 is typically given as an intramuscular injection (shot). An injection of 1000 micrograms (1 mg) of vitamin B-12 is generally given every day for one week, followed by 1 mg every week for four weeks and then 1 mg every month thereafter.

Alternative treatments for pernicious anemia include high-dose oral vitamin B-12, since a lower-efficiency absorption system for vitamin B-12 exists in the intestine that does not require the presence of IF. However, the oral dose required for this type of therapy (1 to 2 milligrams/day) is more than 200 times higher than the minimum daily vitamin B-12 requirement for adults and is significantly higher than that available in most standard multivitamins and B-12 supplements. Nasal spray and sublingual (under the tongue) preparations of vitamin B-12 are also available and are under investigation.

Prognosis

Prognosis of Anemia (Pernicious)
If untreated, the neurological complications of pernicious anemia can be permanent and end in death, but pernicious anemia is easily and effectively treated by the administration of vitamin B-12. Life-long treatment is required.

People with pernicious anemia have a slightly increased risk of stomach cancer when compared to the normal population. The incidence of stomach cancer in people with pernicious anemia is 2-3 times higher than in the general population of the same age.

Prevention

Prevention of Anemia (Pernicious)
The autoimmune process that causes pernicious anemia cannot be prevented. Vitamin B-12 deficiency that is caused by conditions such as other gastrointestinal diseases and gastrointestinal surgery is preventable only to the extent that these causative conditions themselves are preventable.

Vitamin B-12 is derived from animal (for example, meat, fish, poultry, milk) sources, but vitamin B-12 deficiency in vegetarians or vegans can be prevented by the use of oral vitamin B-12 supplements. An oral dose of 100-200 micrograms (mcg) taken weekly is sufficient. Pregnant and nursing women who are vegetarians or vegan should take a B-12 supplement and inform their doctors they are vegetarians or vegan.