What does Anemia, pernicious mean?

Anemia, pernicious meaning in Medical Dictionary

minimal red bloodstream cell matter caused by insufficient vitamin B12. Abbreviated PA. Patients with PA cannot produce intrinsic element (IF), a substance that allows the human body to soak up vitamin B12 from foods. The ensuing inadequacy of vitamin B12 hampers the production of purple blood cells. PA can be treated by injection of supplement B12: dental administration cannot work because individuals with PA cannot absorb by mouth administered supplement B12. Also known as Addison's anemia.