Pernicious anemia is a potentially fatal nutritional deficiency cause by the body's inability to absorb vitamin B-12, which is essential to the body's production of red blood cells.
Pernicious anemia is caused by the absence of intrinsic factor, a substance secreted by the stomach.
Intrinsic factor facilitates the absorption of vitamin B-12. A blood test can confirm a diagnosis of pernicious anemia, by revealing the presence of megaloblasts in the blood. A megaloblast is a large erythroblast, and an erythroblast is the first identifiable stage in the development of a red blood cell. In pernicious anemia, the number of red blood cells decreases, but their size and hemoglobin content increases. Because the body stores B-12 very efficiently, it takes years for pernicious anemia to develop and for symptoms to begin to show.