Pernicious Anemia

At a glance

Type of vitamin B12 deficiency resulting from decreased production and availability of intrinsic factor secondary to autoimmune induced gastric mucosa atrophy and lack of gastric parietal cells.

Synonyms

Biermer-Ehrlich Anemia; Hunter-Addison Anemia; Lederer Anemia; Macrocytic Achylic Anemia; Biermer Anemia; Addison-Biermer Anemia.

Incidence

It affects males and females equally. The most common form, Adult Onset Pernicious Anemia, affects people after the age of 35 years. Studies suggest that about 1.9% of the elderly population is affected. Congenital Pernicious Anemia is very rare and has an onset of age between 4 and 28 months. Juvenile Pernicious Anemia has symptoms similar to the adult-onset type, seems to occur between the ages of 4 and 20 years. North America and in Europe among people of Scandinavian, English, or Irish descent has the higher prevalence. It is extremely rare among Asians. Approximately 1.9% of cases may go undiagnosed. Pernicious anemia shows a 10-fold increase in patients with multiple myeloma and a 250-fold increase in adults with immunoglobulin deficiency.

Genetic inheritance

Autosomal dominant inheritance with incomplete penetrance.

Pathophysiology

Autoantibodies against gastric parietal cells account for the defect in intrinsic factor production and availability. Parietal cells produce hydrochloric acid and an intrinsic factor required for vitamin B12 uptake. The resultant vitamin B12 deficiency produces megaloblastic changes in red cells and neuropathies. The latter result from demyelination with the accumulation of odd-chain fatty acids secondary to impaired cobalamin-dependent degradation of methylmalonyl coenzyme A to succinyl-CoA.

Diagnosis

Decreased oral absorption of cobalt-60-labeled vitamin B12.

Clinical aspects

Usual symptoms of anemia. Sore tongue. Patients may present with symptoms and signs of lateral and posterior spinal column involvement with progression to paraplegia and bowel/bladder dysfunction if left untreated.

Precautions before anesthesia

Patients with anemia should have the red cell indices examined to exclude megaloblastic changes. Document preexisting neurologic deficits. Investigations: complete blood count (CBC), red cell indices.

Anesthetic considerations

Avoid nitrous oxide administration in patients with increased mean corpuscular volume or in patients with documented vitamin B12 deficiency. Regional anesthesia may be relatively contraindicated in patients with preexisting neurologic deficits.

Pharmacological implications

Irreversible oxidation of coenzyme B12 and methionine synthase by N₂O. It has been shown that patients with preexisting B12 deficiencies can develop megaloblastic anemia and neurologic deficits after 2 hours or less of nitrous oxide exposure. The neurologic deficits developed 2 to 6 weeks postoperatively and improved with B12 therapy.

Other conditions to be considered

• Congenital Transcobalamin II Deficiency (Transcobalamin II Deficiency; Grasbeck-Imerslund Disease): Retinal ...