Pernicious anaemia Dr Rob Hicks A lack of vitamin B12 causes the condition, but once this form of anaemia is diagnosed, it can be treated effectively.

In this article

What is pernicious anaemia? Symptoms

Causes and risk factors Treatment and recovery

Advice and support

'Pernicious' means having a harmful affect, often in a gradual or subtle way, and anaemia means a low level of red blood cells. However the name pernicious anaemia is used for a specific condition where the body is unable to absorb enough vitamin B12 into the body from the gastro-intestinal tract.

The symptoms of anaemia include tiredness, light-headedness, shortness of breath and heart palpitations. Other symptoms that may arise from a vitamin B12 deficiency are soreness of the tongue and mouth, weight loss and bouts of diarrhoea. Vitamin B12 is also needed to help keep nerves healthy, so if a deficiency isn't treated there may be tingling and numbness in the fingers and toes, weakness and balance problems, memory loss and confusion.

Pernicious anaemia is caused by a lack of vitamin B12. This vitamin is vital for the manufacture of new red blood cells. When it's in short supply, red blood cells are produced in smaller numbers, are abnormally large in size (megaloblastic) and don't last as long as they should. Consequently, anaemia develops.

Pernicious anaemia develops when the body becomes unable to absorb vitamin B12 properly from food. Normally a protein known as intrinsic factor, which is made in the stomach, attaches to vitamin B12 and carries through the intestinal wall into the blood stream. However in pernicious anaemia, the stomach cells that produce intrinsic factor become damaged, vitamin B12 is no longer absorbed and a deficiency develops, leading to anaemia.

Such damage can occur as the result of an autoimmune disorder, where the body attacks itself. This tends to run in families and is more likely to occur if someone already has had other auto-immune diseases of the hormone glands such as thyroid disease or diabetes.

Anything that reduces the number of intrinsic factor-producing cells - for example, stomach surgery, ulcers or cancer of the stomach - may also result in deficiency. One of the commonest causes is simply thinning or atrophy of the cells that line the stomach, which occurs with age. This partly explains why pernicious anaemia is most common in older people - around one in 8,000 people over the age of 60 has pernicious anaemia and it is much more common among those over 80. It also affects women more than men.

Vitamin B12 deficiency can also occur for reasons other than pernicious anaemia. In some people, the deficiency arises because there is just not enough B12 in the diet. Vitamin B12 is only found in foods of animal origin, such as meat, fish, cheese, eggs and milk, so a strict vegetarian or vegan diet, without vitamin supplements, can lead to a deficiency. Vegans in particular should make sure their diet includes food fortified with B12.

Other causes of B12 deficiency include certain medicines (especially some used for tuberculosis), heavy infestations of intestinal parasites, and rare metabolic disorders.

A simple blood test can diagnose anaemia and an examination of the red blood cells can determine whether they're larger than normal. If this is the case a Schilling test, which measures the body's ability to absorb vitamin B12 from the bowel, will determine whether it's pernicious anaemia. However for most people on a normal diet, especially the elderly, a Schilling test is not thought necessary. Instead, a blood test is done to measure levels of vitamin B12 (and also folate – another nutrient which, if deficient, can cause megaloblastic anaemia). If B12 levels are low, pernicious anaemia is presumed and treatment started.

Treatment for pernicious anaemia is highly effective and involves an injection of vitamin B12 (it isn't absorbed properly if given by mouth). Once the deficiency has been corrected, a maintenance dose of vitamin B12 is given every three months for life. With treatment, the majority of people make a full recovery.

Pernicious Anaemia Society

Website: www.pernicious-anaemia-society.org

This article was last medically reviewed by Dr Trisha Macnair in May 2009.