Intrinsic factor is a binding protein required for the absorption of vitamin B12. Pernicious anemia results from a lack of intrinsic factor in gastric secretions which, in turn, causes inadequate vitamin B12 absorption. Vitamin B12 deficiency is the result. The vitamin B12 deficiency causes a form of anemia specifically referred to as megaloblastic anemia . A lack of intrinsic factor is the most common cause of vitamin B12 deficiency.
Intrinsic factor is produced by cells within the stomach.
In adults, the inability to make intrinsic factor is the result of chronic gastritis or is the result of gastrectomy. The onset of the disease is slow and may span decades. Very rarely, infants and children lack the ability to produce effective intrinsic factor. This form of congenital pernicious anemia is inherited as an autosomal recessive disorder. However, most often, megaloblastic anemia in children results from other causes of vitamin B12 deficiency or other vitamin deficiencies.