Pernicious Anemia:

A severe anemia caused by inadequacy in "intrinsic factor" that, in turn, is needed for absorption of vitamin B12. 

A Condition caused by vitamin B12 deficiency and characterized by anemia and spinal-chord abnormalities. 

A form of anemia, which means less than the normal level of circulating red blood cells. This condition is caused by an inappropriate autoimmune process in which the immune system attacks and damages certain cells lining the stomach. As a result, vitamin B12 is not absorbed properly from food that is consumed. Vitamin B12 is necessary for proper red blood cell production.