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Pernicious anaemia and other B vitamin deficiencies

Vitamin B12 is found only in animal foods including meat, dairy and egg products. Very strict Vegan vegetarians require vitamin B12 supplements to remain healthy.

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. It 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.

Other causes of vitamin B12 deficiency and anaemia include 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.

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

  • weakness or tiredness
  • lack of energy
  • numbness and tingling that start first in the hands and feet
  • lemon discolouration of the skin (a combination of anaemia and mild jaundice)

 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. Some breakfast cereals are fortified with folic acid. Folic acid is needed during pregnancy for normal development of the baby’s 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 (e.g. “spina bifida”).

Anaemias resulting from vitamin B12 or folate deficiency are sometimes referred to as macrocytic anaemia because red blood cells are larger than normal, or “megaloblastic” due to abnormally large immature red cells in the bone marrow. 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 differential. In pernicious anaemia or vitamin B12 deficiency, these usually show:

  • A low haemoglobin level
  • For red cell indices, the mean corpuscular volume (MCV), which is the average size of RBCs, is often high

A blood film will reveal red blood cells that are abnormally large, abnormally shaped, and sometimes occasional giant white blood cells.

Folic acid deficiency leads to 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 requested to make the diagnosis. Some of these include:

Sometimes a bone marrow aspiration may be performed. This may reveal larger than normal sizes in the cells that eventually mature and become RBCs (“megaloblastic” precursors) or giant immature white blood cells.

Treatment in these conditions involves supplementation with the vitamin that is deficient. Vitamin B12 is usually given by injection, typically every 3 months , although tablets can sometimes be given. 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

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