Pernicious anemia is basically a condition in which the parietal cells of stomach have been destroyed by an autoimmune disease.Parietal cells when functional release an intrinsic factor,so when these cells are dead they won't release the intrinsic factor.the function of intrinsic factor is to bind with vitamin B12 to form intrinsic factor and vitamin B12 complex.As a result the intrinsic factor carries vitamin B12 towards the small intestines(ileum)site of absorption.But in the absence of gastric parietal cells,no intrinsic factor is released and vitamin B12 is digested by the gastric enzymes.Therefore,this vitamin is prevented from being absorbed.Vitamin B12 or COBALAMIN is one of the maturation factors required for the maturation of red blood cells.so in the absence of this vitamin RBCs don't get mature and as a result oxygen will not be delivered properly to the body tissues and a person becomes anemic.Pernicious anemia is treated by giving large does of Vitamin B12 intramuscularly to the patient.It is a heriditary disease.
