Pernicious Anemia

– A chronic, progressive anemia characterized by the production of megaloblasts, which are enlarged red blood cells with an immature nucleus.

Causes and Incidence

Pernicious anemia usually is caused by a deficiency in or underutilization of vitamin B12. It is a fairly common anemia in adults over 50 years of age who are of Scandinavian origin.

Disease Process

Most commonly, the gastric mucosa develops a defect caused by an unknown factor and atrophies. This inhibits the secretion of intrinsic factor (IF), which binds and transports dietary vitamin B12 to the ileum for absorption. The lack of IF prevents vitamin B12 from entering the body, and existing stores of the vitamin are depleted, leading to the production of enlarged, immature RBCs.


Usual signs and symptoms associated with anemia (pallor, fatigue, weakness, dyspnea) plus symptoms that stem from the physiologic changes in the gastrointestinal tract (e.g., glossitis, gingivitis, indigestion, epigastric pain, loss of appetite, diarrhea, constipation, weight loss). Peripheral neurologic changes occur, with paresthesia in the hands and feet.

Potential Complications

If the condition goes untreated, the neurologic changes become more profound, with involvement of the spinal cord and loss of vibratory sense, ataxia, spasticity, and disturbances in bowel and bladder function. Depression, paranoia, and delirium may follow. Splenomegaly and hepatomegaly occur, as well as organ failure, neurologic degeneration, or infection, eventually causing death.

Diagnostic Tests

Peripheral blood smear
Oval macrocytes, hypersegmented neutrophils, enlarged platelets.

Schilling test
Radioactive-tagged vitamin B12 is not excreted in urine.

Complete blood count
Decreased Hgb, leukocytes, erythrocytes, and thrombocytes.

Bone marrow aspiration
Hyperplasia; increased large-cell megaloblasts.

Gastric analysis
Lack of free hydrochloric acid.


Surgery – None.

Lifelong parenteral vitamin B12 replacement (dietary vitamin B12 replacement is not effective); oral iron if Hgb does not rise.

Treatment of underlying cause of gastric atrophy, if possible; oxygen to increase arterial levels; oral hygiene; orientation if confused; safety precautions for neurologic effects; instruction about vitamin B12 replacement as a life change.