DefinitionPernicious anemia is a decrease in red blood cells that occurs when the body cannot properly absorb vitamin B12 from the gastrointestinal tract. Vitamin B12 is necessary for the proper development of red blood cells.Pernicious anemia is a type of megaloblastic anemia.See also: AnemiaAlternative NamesMacrocytic achylic anemia; Congenital pernicious anemia; Juvenile pernicious anemia; Vitamin B12 deficiency (malabsorption)Causes, incidence, and risk factorsThe body needs vitamin B12 to make red blood cells. To provide vitamin B12 to your blood cells, you need to eat enough foods containing vitamin B12, such as meat, poultry, shellfish, eggs, and dairy products.To absorb vitamin B12, your body uses a special protein called intrinsic factor, which is released by cells in the stomach.