Monarch Disease Ontology id MONDO_0008228 (pernicious anemia) is megaloblastic anemia caused by vitamin B-12 deficiency due to impaired absorption. The impaired absorption of vitamin B-12 is secondary to atrophic gastritis and loss of gastric parietal cells. Also known as: Addison anaemia, Addison anemia, Addison's anaemia, Addison's anemia, Addison-Biermer anaemia, Addison-Biermer anemia, Biermer anaemia, Biermer anemia.