Vitamin B12 Deficiency Terminology
Vitamin B12 deficiency is most commonly called "pernicious anemia" when caused by autoimmune destruction of gastric parietal cells leading to intrinsic factor deficiency, though the term "vitamin B12 deficiency" itself encompasses all causes of cobalamin insufficiency. 1, 2
Understanding the Terminology
The naming depends on the underlying cause:
Pernicious anemia specifically refers to vitamin B12 deficiency caused by autoimmune atrophic gastritis that destroys parietal cells, leading to intrinsic factor deficiency or the presence of autoantibodies against intrinsic factor 2, 3
Megaloblastic anemia describes the hematologic manifestation of vitamin B12 deficiency, characterized by abnormally large red blood cells due to impaired DNA synthesis 4, 3
Cobalamin deficiency is the technical term using the scientific name for vitamin B12 2
Clinical Context
The distinction matters because:
Pernicious anemia represents approximately 4% prevalence among Europeans and is the most common autoimmune cause of B12 deficiency 5
Patients with pernicious anemia require lifelong monthly vitamin B12 injections, as the underlying absorption defect cannot be corrected 4
The presence of parietal cell antibodies or intrinsic factor antibodies confirms the autoimmune etiology 2
Important Clinical Caveat
If vitamin B12 deficiency progresses untreated for longer than three months, it may produce permanent degenerative lesions of the spinal cord, making early recognition critical. 4 The neurologic manifestations include subacute combined degeneration of the spinal cord, which can become irreversible if treatment is delayed 4, 2