Pernicious anaemia is an autoimmune disorder in which the body fails to produce enough healthy red blood cells. It is a severe anaemia caused by the diminution or absence of stomach acid secretion, with consequent failure of the gastric mucosa to secrete the intrinsic factor necessary for the absorption of vitamin B12, characterised by a great reduction in the number of red blood cells and an increase in their size.
Vitamin B12 and Intrinsic Factor
Vitamin B12, also called cobalamin, has the formula C63H88CoN14O14P.
It is a water soluble vitamin that plays a key role in the normal functioning of the brain and nervous system and in the formation of blood.
Neither fungi, nor plants, nor animals are capable of producing vitamin B12. Only bacteria have the enzymes required for its synthesis, although many foods are natural sources of vitamin B12 because of bacterial symbiosis. Hence we must obtain our vitamin B12 from our food.
Vitamin B12 was discovered from its relationship to the disease pernicious anaemia, an autoimmune disease in which the parietal cells of the stomach responsible for secreting intrinsic factor are destroyed, the same cells responsible for secreting acid in the stomach. Intrinsic factor is a protein crucial for the normal absorption of B12 in the ileum of the small intestine, so lack of intrinsic factor, as seen in pernicious anaemia, causes a B12 deficiency.
Other conditions and factors that can cause B12 deficiency include infections, surgery, medicines and diet.
Vitamin B12 deficiency is also called cobalamin deficiency.
While the term 'pernicious anaemia' is sometimes incorrectly used to indicate megaloblastic (large cells) anaemia due to any cause of B12 deficiency, its proper usage refers only to that caused by atrophic gastritis, parietal cells loss, and lack of intrinsic factor. The loss of the ability to absorb vitamin B12 (due to absent or reduced intrinsic factor) is the most common cause of adult B12 deficiency.
Historically, pernicious anaemia was detected only after it became 'clinical' (caused an overt disease state) and the anaemia was well established, ie the liver stores of B12 had been depleted. The pernicious aspect of the disease - prior to the discovery of treatment - was its invariably fatal prognosis. Pernicious actually means "deadly". It is now possible to diagnose B12 deficiency before it leads to clinical symptoms. With appropriate treatment, the patient never becomes ill.
The term anaemia refers to a condition in which the blood has a lower than normal number of red blood cells. The various anaemias, including a brief description of pernicious anaemia, have been described in my October 2010 newsletter Anaemia.
In pernicious anaemia, the body can't make enough healthy red blood cells because it doesn't have enough vitamin B12. Without enough B12, the red blood cells don't divide normally and are too large (macrocytic).
Other Names for Pernicious Anaemia
Pernicious anaemia is one of the two major types of ‘macrocytic’ or ‘megaloblastic’ anaemias. These terms refer to anaemia in which the red blood cells are larger than normal. The other major type of macrocytic anaemia is caused by folic acid deficiency.
Causes of Pernicious Anaemia
The lack of intrinsic factor, as indicated above, is the true cause of vitamin B12 deficiency leading to pernicious anaemia. An autoimmune response occurs if the body's immune system makes antibodies (proteins) that mistakenly attack and damage the body's tissues or cells. In pernicious anaemia the antibodies attack and destroy the parietal cells which line the stomach and make intrinsic factor.
A positive family history is a risk factor.
Other causes of ‘pernicious anaemia’ (the non-autoimmune type) include malabsorption in the small intestine of vitamin B12. These include:
- Too many of the wrong kind of bacteria on the small intestine
- Disease that interfere with vitamin B12 absorption such as coeliac disease
- Certain medicines such as antibiotics and certain diabetes and seizure medications
- A lack of intrinsic factor can also occur if part of the stomach has been removed surgically.
- Infection by the tapeworm diphyllobothrium latum, which feeds on vitamin B12. This is a tapeworm found in raw fish.
- The elderly and those with alcoholism are at risk.
Another cause of B12 deficiency can be diet. Some people get pernicious anaemia because they do not have sufficient vitamin B12 in their diets. This is a rare cause, but may occur in strict vegetarianism. Food sources of vitamin B12 include:
- Breakfast cereals with added vitamin B12
- Meats, poultry and fish
- Eggs and dairy products
- Foods fortified with vitamin B12. Vitamin B12, in the form of cyanocobalamin, is used to fortify foods and in natural supplements. It contains a trace of (bound) cyanide.
If you are a strict vegetarian, the B12 levels should be checked regularly.
Signs and Symptoms of Pernicious Anaemia
These include the signs and symptoms of anaemia and those that are specific for vitamin B12 deficiency.
- Symptoms of anaemia in general, which include:
- Fatigue and Tiredness. This is the most common symptom. Fatigue occurs because the body does not have enough red blood cells to carry oxygen to its various parts.
- Shortness of breath
- Coldness in hands and feet
- Chest pain
- Irregular heart beat and palpitation.
- Vitamin B12 deficiency may lead to nerve damage. These nerve symptoms are the result of subacute combined degeneration of the (spinal) cord. There is degeneration of the posterior and lateral columns of the spinal cord as a result of vitamin B12 deficiency. (It can also be the result of copper deficiency and vitamin E deficiency.) Symptoms progressively worsen without treatment. Nerve damage symptoms include:
- Tingling and numbness in hands and feet
- Muscle weakness
- Weakness of the legs, arms and trunk
- Loss of reflexes
- Loss of balance, with trouble walking.
- Severe deficiency can cause confusion, dementia, depression, memory loss.
- Vitamin B12 deficiency may lead to digestive symptoms, including:
- Abdominal bloating
- Loss of appetite
- Weight loss
- A smooth, thick, red tongue is a sign of vitamin B12 deficiency and pernicious anaemia.
The diagnosis is based on the clinical history, physical examination and blood test results.
The blood tests include a full blood count, looking at the number and characteristic of the red blood cells, the amount of haemoglobin (the iron-rich protein that helps the red blood cells carry oxygen), and the haematocrit (a measure of how much space the red blood cells take up, in the blood). A low level of haemoglobin or haematocrit is a sign of anaemia. In pernicious anaemia, the red blood cells are larger than normal and fewer in number. The other blood cells (white cells of several types and platelets) are also measured.
Other blood tests include vitamin B12 levels, intrinsic factor antibodies and parietal cell antibodies, serum folate, iron and iron binding capacity and reticulocyte count (a measure of the number of young red blood cells in the blood ... the count is low in pernicious anaemia).
A bone marrow biopsy may be necessary to access the health of the bone marrow.
Treatment of Pernicious Anaemia
The goals of treating pernicious anaemia include
- Preventing or treating the anaemia and its signs and symptoms
- Preventing or managing complications such as nerves damage
- Treating the cause of the pernicious anaemia - if a cause can be found.
Treatment is easy: Vitamin B12 injections. These will be required for life if the pernicious anaemia is due to destruction of the cells producing the intrinsic factor. In the absence of intrinsic factor, vitamin B12 can not be absorbed.
With proper treatment, people who have pernicious anaemia can reverse the anaemia, feel well and live normal lives, with B12 treatment. If there are complications of pernicious anaemia such as nerve damage, early treatment may help reverse the damage.
*Copyright 2015: The Huntly Centre.
Disclaimer: All material in the huntlycentre.com.au website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.Back to the list Print friendly version