What is the definition or description of: pernicious anemia?

Vitamin deficiency: Pa is due te either vitamin B12 or folate (folic acid) deficiency. Originally it was found that the "intrinsic" factor (produced in the stomach) was missing and this is an essential element for the absorption of b12. Any cause of B12 or folate (folic acid) deficiency results in changes in the blood by which it can be recognized.

See below: Pernicious anemia results from the inability to absorb vitamin B12 normally due to a lack of intrinsic factor, a substance required for adequate B12 absorption. This leads to macrocytic anemia; large red blood cells. It is no longer "pernicious" as it is easily treated with either large doses of oral vitamin B12 , or injectable vitamin b12.

Due 2 B12 deficiency: It is a decline in the amount of red cells in the circulation as a result of impaired production in the bone marrow resulting from a lack of vitamin b12. This is most commonly as a consequence of impaired absorption due to an autoimmune condition affecting the stomach lining. If untreated, it may also lead to brain and spinal cord problems. It is easily treatable with replacement therapy.