Pernicious anemia is one of two major types of "macrocytic" or "megaloblastic" anemia. These terms refer to anemia in which the red blood cells are larger than normal. (The other major type of macrocytic 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.
Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.