Pernicious anemia is due to vitamin B12 deficiency, which leads to a low level of red blood cells. Because nerve cells also need B12, neurological symptoms such as dizziness, numbness and tingling in the hands and feet, and muscle weakness may show up even before the anemia is diagnosed. It is unlikely that your sister's condition is related to lack of B12 in her diet. Although we get this vitamin only from animal foods (such as meat, fish, eggs or dairy products), we need so little of it that dietary deficiencies tend to develop only among strict vegetarians (vegans) who eat no animal products, especially vegan children. In people your sister's age or older, pernicious anemia is almost always due to low intrinsic factor, a protein produced in the stomach that is necessary for B12 absorption. Failure to produce intrinsic factor can be genetic in origin or caused by atrophy of the stomach lining or autoimmunity. Other causes of B12 deficiency include gastric surgery, abnormal bacterial growth in the small intestine, certain infections (especially tapeworms from fish) or intestinal disorders such as Crohn's disease and celiac disease. Overall, pernicious anemia develops in two percent of the over-60 population; slightly more women than men are affected. Risks are highest among people who have autoimmune endocrine diseases.
Symptoms of vitamin B12 deficiency tend to come on so slowly that they may not be recognized for some time. They include fatigue, weakness, shortness of breath, dizziness, heart palpitations, bleeding gums and mouth sores, a red, beefy-looking tongue, nausea or poor appetite and diarrhea.
While pernicious anemia can't be reversed, B12 shots to correct the vitamin deficiency usually can eliminate symptoms and restore the body's production of red blood cells. At first, patients may get several shots to correct the deficiency and then regular injections every one to three months to maintain adequate B12 levels.
In addition to your sister's regular B12 shots, I recommend that she make sure that she's getting adequate folic acid, also needed for blood cell production. Apart from that, no special diet or supplements are necessary.
Andrew Weil, M.D.