Pernicious anemia

Pernicious anemia (also known as Biermer's anaemia or Addison's anaemia or Addison-Biermer anaemia) is a form of megaloblastic anaemia due to vitamin B12 deficiency dependent on impaired absorption of vitamin B12 in the setting of atrophic gastritis, and more specifically of loss of gastric parietal cells. While the term "pernicious anaemia" is sometimes also incorrectly used to indicate megaloblastic anaemia due to any cause of vitamin B12 deficiency, its proper usage refers to that caused by atrophic gastritis and parietal cell loss only.