ANEMIA, PERNICIOUS

Pernicious anemia is deficiency of red blood cells and hemoglobin that results from a deficiency or abnormal absorption of cobalamin (vitamin B₁₂). This vitamin is essential for normal growth and development of red blood cells, other blood cells, and cells of the nervous system. Insufficient intake of vitamin B₁₂ rarely causes anemia. Most frequently, absence of a specific protein, intrinsic factor, necessary for absorption of vitamin B₁₂ causes pernicious anemia. This occurs when the immune system attacks the cells of the stomach lining and prevents them from producing intrinsic factor. Other mechanisms include absence of the stomach or small intestine after an operation, tapeworm infestation, or tropical sprue.

Pernicious anemia is rare. Both sexes are affected equally. This form of anemia rarely occurs before 30 years of age. It is more common among persons of northern European descent.

The diagnosis of pernicious anemia is made by means of microscopic examination of the blood and measurement of vitamin B₁₂ and the products of its breakdown in the blood. Special tests may be needed to observe abnormal absorption of the vitamin (Schilling test) and document the presence of specific antibodies.

Supplementation of vitamin B₁₂ leads to full correction of anemia. Patients with deficient absorption of the vitamin need long-term supplementation.

Anemia becomes apparent as fatigue and poor exercise tolerance. In severe cases anemia can cause chest pain, shortness of breath, and a rapid heartbeat. Patients with pernicious anemia, however, almost never need blood transfusions. Deficiency of vitamin B₁₂ can produce decreased sensation and numbness in the feet and hands. Severe deficiency can cause severe neurologic deficits, such as confusion and disorientation, but this is rare.

Therapy for pernicious anemia is administration of vitamin B₁₂ as injections under the skin or into the muscle. Initial treatment involves daily injections followed by weekly and eventually monthly injections. Improvement in the sense of well-being occurs in a matter of days. It takes 4 to 8 weeks to demonstrate an increase in hemoglobin concentration. Treatment is lifelong. Patients with insufficient intake can take oral vitamin B₁₂. There are no known side effects or complications of taking vitamin B₁₂. Vitamin B₁₂ is also available as a gel solution for intranasal administration (Nascobal), which is administered via a metered dose nasal inhaler once weekly in place of monthly injections. Intranasal administration for maintenance therapy of pernicious anemia should be used only after the initial deficiency has been corrected with vitamin B₁₂ injections. Medical supervision is necessary for the initial treatment with vitamin B₁₂, because lowering of blood potassium level may occur. A simple blood test can determine this. Potassium taken as a pill corrects this temporary problem.

• Continue treatment on a monthly basis (if injections are used), even if the anemia is corrected. Discontinuation of treatment leads to recurrence of anemia and all the symptoms.
• Follow the schedule of vitamin B₁₂ injections recommended by your physician.
• Discuss a supplementation schedule with your physician if you are pregnant.
• Eat a well-balanced diet, rich in folic acid (another vitamin important for the blood cells) and other essential nutrients.
• Supplement your diet with oral vitamins if you eat a special diet, such as a vegetarian (especially vegan) diet.

• Avoid exercise until the anemia is corrected.

• If you experience any signs of severe anemia, such as chest pain, palpitations, or shortness of breath.

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