This disease is characterized by the deficiency of vitamin B12 due to the presence of anti-intrinsic factor and anti-parietal cell antibodies which inhibit the absorption of the vitamin B12.
Diagnosis of PA relies on histologically proven atrophic body gastritis, peripheral blood examination showing megaloblastic anemia with hypersegmented neutrophils, cobalamin deficiency and antibodies to intrinsic factor and to gastric parietal cells.