Darleen Hall, age 11, of Inola, Okla., for her question:

WHAT IS PERNICIOUS ANEMIA?

Anemia is not in itself a disease but a symptom of one. Anemia occurs when the number of red blood cells or the amount of red pigment in the blood falls below normal.

Pernicious anemia usually results when there is not enough vitamin B 12 in the body. This may happen when the stomach fails to produce a substance called " intrinisic factor," or when the intestines fail to either absorb vitamin B 12 or intrinsic factor. As a result, the red blood cells are not formed properly.

Regular hypodermic injections of vitamin B 12 are often prescribed by a doctor when pernicious anemia is discovered. The injections will keep the blood normal.

To make red blood cells, the body's bone marrow needs iron, vitamin B 12 and certain proteins.