Pernicious anemia is a type of megaloblastic anemia caused by a deficiency of vitamin B₁₂. This condition can also be called Addison's anemia.

Vitamin B₁₂ deficiency anemia is when there are low levels of circulating vitamin B₁₂. When there is a lack of vitamin B₁₂, the body does not have enough healthy red blood cells.

Pernicious anemia may result from a genetic predisposition, or an inherited autoimmune response. Pernicious anemia refers to a vitamin B₁₂ deficiency anemia that results from lack of intrinsic factor, a glycoprotein secreted by the stomach that enables the small intestine to absorb vitamin B₁₂. When there is a lack of the intrinsic factor, vitamin B₁₂ cannot be absorbed into the body which results in the blood not being able to make enough healthy red blood cells.

Vitamin B₁₂ deficiency anemia can result from a diet lacking vitamin B₁₂ (vegan/vegetarian); surgery to the stomach or small intestine (i.e. gastric bypass surgery); or abnormal bacteria growth in the small intestine or an intestinal disease (i.e. Crohn's disease or celiac disease).

Pernicious anemia has an insidious onset and usually occurs among those aged 50-60 years old. Manifestations include:

• weakness

• sore tongue

• numbness and tingling in the extremities

• pale lips

• gums and tongue

• faintly jaundiced sclerae

• pale, bright yellow skin

• ndicators of infection, especially of the genitourinary tract

• vomiting

• anorexia

• weight loss

• flatulence

• diarrhea

• constipation

• bleeding of the gums

• glossitis

• neuritis

• disturbed position sense

• lack of coordination

• ataxia

• impaired fine finger movement

• positive Babinski's and Romberg's signs

• altered vision

• irritability

• poor memory

• headache

• depression

• delirium

• impotence

The hemoglobin ranges from 5gm/100ml or less to 10gm/100ml or less in anemia.

Vitamin B₁₂ deficiency anemia symptoms are similar to that of pernicious anemia, and include weak muscles, numb or tingling feeling in hands and feet, trouble walking, nausea, decreased appetite, weight loss, irritability, fatigue, diarrhea, smooth and tender tongue, fast heart rate.

Tests include:

• the Schilling test

• therapeutic trial of vitamin B₁₂ injections to distinguish between iron-deficiency anemia and pernicious anemia

• complete blood count (CBC)

• blood serum chemistry

• bone marrow aspiration

• biopsy

Treatment for pernicious anemia includes parenteral vitamin B₁₂. If the hemoglobin level is dangerously low, blood transfusions are given. Antibiotics are used if there is an accompanying infection. A well-balanced diet and avoidance of foods that irritate the mouth are recommended.

Treatment for vitamin B₁₂ deficiency includes a well-balanced diet with foods rich in vitamin B₁₂, or supplements. Vitamin B₁₂ is not as well absorbed by mouth as by injection.

Monthly vitamin B₁₂ injections would be required indefinitely in pernicious anemia. There may also be irreversible central nervous system changes in pernicious anemia which may have occurred before treatment and continue to persist after treatment.

• Prior to December 9, 2018, this condition was evaluated under diagnostic code 7700.

• Consider service connection for primary anemia on a presumptive basis as a chronic condition (38 CFR 3.307; §3.309(a)).

• A 100 percent evaluation for pernicious anemia and Vitamin B₁₂ deficiency shall be assigned as of the date of the initial diagnosis requiring transfusion due to severe anemia or parenteral B₁₂ therapy and shall continue with a mandatory VA examination six months following hospital discharge or cessation of parenteral B₁₂ therapy. Any reduction in evaluation based upon that or any subsequent examination shall be subject to the provisions of 38 CFR  §3.105(e). Thereafter, evaluate at 10 percent and separately evaluate any residual effects of pernicious anemia, such as neurologic involvement causing peripheral neuropathy, myelopathy, dementia, or related gastrointestinal residuals, under the most appropriate diagnostic code.