Pernicious anemia or vitamin B12 deficiency

Definition
Anemia is a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron. The red blood cells carry oxygen throughout the body.

Causes/associated factors
Pernicious anemia, a specific type of anemia, is caused by a vitamin B12 (cobalamin) deficiency. With pernicious anemia, your body doesn't absorb enough vitamin B12, and you won't be able to produce an adequate amount of red blood cells.
Normally, a substance called intrinsic factor is secreted from the lining of the stomach to help the body absorb vitamin B12 from the gastrointestinal tract. Pernicious anemia occurs when the intrinsic factor is missing. Researchers don't know for sure why some people are missing the intrinsic factor, but most experts agree it's an autoimmune condition (when the body produces antibodies to fight against its own tissues) that some people are simply genetically predisposed to develop. It's most common in people of northern European descent. This autoimmune disease often follows chronic gastritis (inflammation of the stomach lining).

Anemia because of a vitamin B12 deficiency can also be caused by other factors, but it's not true pernicious anemia. Nutritional deficiencies, problems with the small bowel (where vitamin B12 is absorbed), stomach surgeries and even substances that compete with the absorption of vitamin B12, such as certain medications or alcohol, can all cause anemia.

The recommended daily allowance of vitamin B12 for adult men and women is 2.4 micrograms. Food sources of vitamin B12 include animal protein foods such as liver, kidney, meat, fish (such as cooked salmon), milk products, cheese and eggs. The odds of developing a vitamin B12 deficiency increase with a restricted diet that lacks animal protein foods (such as a strict vegan diet).


Signs/symptoms
Symptoms of pernicious anemia may include any of the following:
sore tongue and bleeding gums
pale lips, tongue and gums
extremely pale skin
yellow eyes
tingling and numbness of extremities
tinnitus (ringing in the ears)
appetite loss and weight loss
difficulty maintaining proper balance, poor coordination or dizziness
shortness of breath
palpitations or rapid heartbeat
depression
weakness, headache and fatigue
confusion or dementia
memory loss
prematurely gray hair
abnormal reflexes

Diagnosis
Diagnosis is based on your medical history, a physical exam and blood tests (such as complete blood cell counts and vitamin B12 levels). Depending on the circumstances, a variety of other tests may also be needed. For example, after swallowing a pill of radioactive vitamin B12, the Schilling test tracks how much of the vitamin is excreted in your urine. Bone marrow evaluations may be done to study your red blood cells.

Treatment
Treatment depends on the underlying cause. If you do not have true pernicious anemia but have low vitamin B12 intake due to inadequate nutrition, simple dietary changes may be all that's necessary. If you follow a strict vegetarian diet, vitamin B12 supplements may be prescribed to prevent the development of anemia.
If you're missing the intrinsic factor or the condition is caused by other factors that cannot be changed, regular injections of vitamin B12 may be necessary. These injections must continue indefinitely, usually for life. Treatment often brings quick relief of symptoms, and symptoms often disappear entirely within six months. If you refuse the injections, high doses of oral vitamin B12 may be an option. A new intranasal preparation that may be effective for long-term therapy is also available.

When people who have signs of pernicious anemia are treated with injections of B12 within six months of the condition's appearance, the central nervous system symptoms are usually reversible.


Complications
Prompt treatment is essential. If left untreated, pernicious anemia may cause permanent damage to your nervous system or digestive tract. Other complications may include stomach polyps (growths) or stomach cancer.
During the early stages of treatment with vitamin B12 shots, an electrolyte imbalance is a possibility. (Electrolytes are substances that can transmit electrical impulses when dissolved in body fluids.) Low potassium levels may develop, so careful monitoring during the first few days of treatment is important.


Pregnancy-specific information
The recommended daily allowance of vitamin B12 increases during pregnancy and breastfeeding. During pregnancy, you need 2.6 micrograms of vitamin B12 a day. If you choose to breastfeed, consult your child's doctor if you're a pure vegan or think your diet may be lacking in animal proteins.

Senior-specific information
Anemia due to vitamin B12 deficiency is especially common in older adults, who are more likely to have poor diets that lack vitamins in general. Older adults are also more likely to have other medical conditions that can interfere with dietary intake. If you have any concerns about your diet, consult your doctor.

Prevention
If you have a lack of intrinsic factor, early detection and treatment with vitamin BB12 is needed to help prevent the complications of pernicious anemia. Vitamin supplements may help prevent pernicious anemia related to poor intake of vitamin B12. Consulting a registered dietitian for meal planning may also be helpful.