Pernicious anemia is a medical problem that causes a person to have too few red blood cells (anemia) because their intestines cannot absorb vitamin B12 properly. A special protein, called intrinsic factor, helps the body get vitamin B12 from food such as meat, poultry and dairy foods. Intrinsic factor is made by cells in the stomach. If there is not enough intrinsic factor, the small intestine is unable to get the vitamin B12.
There are several causes of pernicious anemia. These include a weakened stomach lining or a problem with the body's immune system, which causes it to attack the intrinsic factor. In some rare cases it can be passed down through families. Treatment is usually a regular injection of vitamin B12.
Intrinsic factor was discovered by Thomas Addison.