Pernicious anemia is one of two major types of "macrocystic" or "megaloblastic" anemia. These terms refer to anemia in which the red blood cells are larger than normal. (The other major type of macrocystic anemia is caused by folic acid deficiency.)
Rarely, children are born with an inherited disorder that prevents their bodies from making intrinsic factor. This disorder is called congenital pernicious anemia.
Vitamin B12 deficiency also is called cobalamin deficiency and combined systems disease.