Pernicious anemia is a blood disease caused by the lack of a substance (intrinsic factor) that the body needs in order to absorb vitamin B12 from food. Without enough vitamin B12, the body does not produce enough red blood cells, and cells throughout the body do not get the oxygen they need.

In pernicious anemia, the body produces antibodies that either destroy the parietal cells (cells in the stomach that make intrinsic factor) or that block the action of intrinsic factor. A doctor can diagnose this disease by doing a blood test that looks for these antibodies.

Symptoms include weakness, numbness in the hands and feet, loss of appetite, weight loss, and fever. Pernicious anemia can damage the nerve cells in the brain and spinal column.

The treatment for pernicious anemia is supplements of vitamin B12. These may be given as shots, pills, or a nasal spray. Because the body can no longer absorb this vitamin from food, the supplements must be continued for life.

Pernicious anemia most often affects older adults. It is more common among people in certain parts of the world, especially Scandinavia.