Pernicious Anemia is the name given to megaloblastic anemia with a specific etiology. It is due to a deficiency in B12 that is not caused by a lack of the vitamin in the diet nor a lack of absorption due to intestinal disease; instead, it is due to a lack of absorption due to autoimmune causes. The Pernicious Anemia patient makes autoantibodies to the gastric parietal cells which secrete intrinsic factor (IF). If you recall, IF is needed to attach to B12 for absorption. In addition, they can make autoantibodies to IF itself.
Pernicious anemia accounts for approximately 20% - 50% of adult vitamin B12 deficiency cases.
