It occurs most often in Caucasians after age 50. The fundamental defect is a permanent deficiency of the intrinsic factor normally present in gastric juice. In addition to atrophy of gastric mucosa and changes in bone marrow common to all megaloblastic anemias, there is often specific neurologisc changes. Subacute combined degeneration of the spinal cord is a common finding. Degeneration may also occur in peripheral nerves, nerve plexuses of the gastro-intestinal tract, and subcortical areas in the motor region of the brain.
Pernicious anemia is basically a nutritional deficiency disease.
Characteristic blood abnormalities can be corrected by use of folic acid. However, if there is an accompanying deficiency of vitamin B-12, an irreversible degeneration of the spinal cord may take place. The intrinsic factor normally produced by stomach mucosa is necessary in order that B-12 may be absorbed and utilized. In pernicious anemia, the stomach has become unable to produce either the intrinsic factor or hydrochloric acid. Adequate protein is also needed as vitamin B-12 is almost always associated with animal proteins such as liver, kidney, muscle meats, etc.