Pernicious Anemia

n. severe form of anemia affecting mostly older people

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.
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Pernicious anemia is a disease in which the red blood cells are abnormally formed, due to an inability to absorb [more]Pernicious anemia - Community and Resources

Noun
1. a chronic progressive anemia of older adults; thought to result from a lack of intrinsic factor (a substance secreted by the stomach that is responsible for the absorption of vitamin B12)
(synonym) pernicious anaemia, malignant anemia, malignant anaemia
(hypernym) anemia, anaemia
(hyponym) megaloblastic anemia, megaloblastic anaemia

A blood disorder caused by a lack of vitamin B12. Patients who have this disorder do not produce the substance in the stomach that allows the body to absorb vitamin B12.