print   Print full article

Pernicious anaemia and other B vitamin deficiencies

Pernicious anaemia is a condition in which the body does not make enough of a substance called ‘intrinsic factor’. Intrinsic factor is a protein produced by parietal cells in the stomach that binds to vitamin B12 and allows it to be absorbed from the small intestine. Vitamin B12 is important in the production of red blood cells (RBCs). Without enough intrinsic factor, the body cannot absorb vitamin B12 from the diet and cannot produce enough normal RBCs, leading to anaemia. In addition to lack of intrinsic factor, other causes of vitamin B12 deficiency and anaemia include dietary deficiency and conditions that affect absorption of the vitamin from the small intestine such as surgery, certain drugs, digestive disorders (coeliac disease, Crohn’s disease), and infections. Of these, pernicious anaemia is the most common cause of symptoms.

Vitamin B12 deficiency can result in general symptoms of anaemia as well as nerve problems. These may include:

  • weakness or fatigue
  • lack of energy
  • numbness and tingling that start first in the hands and feet

Additional symptoms may include muscle weakness, slow reflexes, loss of balance and unsteady walking. Severe cases can lead to confusion, memory loss, depression and/or dementia.

Folic acid is another B vitamin and deficiency in this vitamin may also lead to anaemia. Folic acid, also known as folate, is found in many foods, especially in green, leafy vegetables. Folic acid is added to most grain products so a deficiency in folic acid is rarely seen in Australia today. Folic acid is needed during pregnancy for normal development of the brain and spinal cord. It is important for women considering pregnancy to take folate supplements before they get pregnant and during pregnancy to make sure they are not folate deficient. Folate deficiency early in pregnancy can cause problems in the development of the brain and spinal cord of the baby.

Anaemias resulting from vitamin B12 or folate deficiency are sometimes referred to as ‘macrocytic’ or ‘megaloblastic’ anaemia because red blood cells tend to be larger than normal. A lack of these vitamins does not allow RBCs to grow and then divide as they normally would during development, which leads to their large size. This leads to a reduced number of abnormally large RBCs and anaemia.

Laboratory tests

Symptoms of anaemia will usually be investigated initially with a full blood count (FBC) and White blood Cell differential. In pernicious anaemia or vitamin B12 deficiency, these usually reveal:

  • A low haemoglobin level
  • For red cell indices, the mean cell volume (MCV), which is the average size of RBCs, is often high.
  • A blood film examination will reveal red blood cells that are abnormally large.

Folic acid deficiency can cause the same pattern of changes in haemoglobin and red cell size as vitamin B12 deficiency. If the cause of your anaemia is thought to be due to pernicious anaemia or dietary deficiency of B12 or folate, additional tests are usually done to make the diagnosis. Some of these include:

  • Vitamin B12 level — blood level may be low when deficient in B12
  • Folic acid level — blood level may be low if deficient in this B vitamin
  • Methylmalonic acid (MMA) — may be high with vitamin B deficiency
  • Homocysteine — may be high with either folate or vitamin B deficiency
  • Reticulocyte count — is usually low
  • Antibodies to intrinsic factor or parietal cell antibodies — may be present in pernicious anaemia

Sometimes a bone marrow aspiration may be performed. This may reveal larger than normal sizes in the cells that eventually mature and become RBCs (precursors).

Treatment in these conditions involves supplementation with the vitamin that is deficient. If the cause of deficiency is the inability to absorb the vitamin from the digestive tract, then the vitamin may be given as injections. Treatment of underlying causes such as a digestive disorder or infection may help to resolve the anaemia.

For more on this, see the article on Vitamin B12 and folate deficiency.

Last Review Date: November 1, 2019