What is the definition or description of: intrinsic factor blocking ab?

Leads to B12 defic: Pernicious anemia is a chronic illness caused by impaired absorption of vitamin b-12 because of a lack of intrinsic factor (if) in gastric secretions. It occurs as a relatively common adult form of anemia that is associated with gastric atrophy and a loss of if production and as a rare congenital autosomal recessive form in which if production is lacking without gastric atrophy.