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(Tuesday, 30th Sep, 2014)
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Haemochromatosis

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Haemochromatosis

What is haemochromatosis?

Haemochromatosis is a genetic disorder where an excessive amount of iron is absorbed from the diet. Normally the liver stores iron for the essential purpose of providing new red blood cells with iron. When excess quantities of iron are stored in the liver it becomes enlarged and liver function becomes impaired. Surplus amounts of iron may also be deposited in the heart, pancreas and kidneys.

What are the symptoms?

Iron builds up slowly so the symptoms may not appear for many years. There is no typical pattern of presentation. Most sufferers will complain of fatigue and exhibit changes in skin pigmentation. The additional symptoms will depend on which target organs are affected. For example, if the pancreas is affected then the patient may complain with symptoms of diabetes. If the heart is affected the patient may complain of a variety of heart related symptoms. These may include decreased exercise tolerance or disturbances of heart rhythm. Sometimes the joints may be affected.

Given the diverse pattern of presentation diagnosis is usually triggered by a strong index of suspicion on the part of the attending doctor.

What are the tests?

The diagnosis is based on blood analysis. Tests include serum ferritin and transferrin saturation.

What is transferrin saturation?

This is an iron transport protein. It carries iron when taken from the gut to the bone marrow and the liver. A transferrin saturation above 50% for women and above 55% for men fasting is very suggestive of haemochromatosis.

What is serum ferritin?

This is an iron storage protein. An elevated result may be due to iron overload, but there are other causes of a high level. The result should be interpreted in combination with transferrin saturation.

Do I need a liver biopsy?

If the above blood tests suggest that the liver is likely to contain excess iron or other blood tests imply any degree of liver inflammation then a biopsy is performed. This test involves removing a small piece of liver tissue with a special biopsy needle which is then examined under microscope and the iron concentration is measured chemically.

The result enables doctors to assess the amount of iron overload and to see if any damage has occurred to the liver tissue. It can exclude any other cause of abnormal test results.

What is a genetic test?

There is now a simple genetic test that can identify the mutation in the gene responsible for causing the absorption of too much iron. This involves a blood test or a simple finger prick test where a small drop of blood is applied to a card. The great benefit of this test is that it allows for whole families to be screened and therefore early detection of the disease before symptoms and tissue damage have occurred.

What does treatment involve?

Treatment is most effective when begun early on in the disease as it can successfully prevent or stop organ damage. If damage has already occurred then treatment should halt any further damage and in most cases bring about an improvement.

The only method of removing excess iron from the body is by removal of blood. This is like giving a blood donation and is called venesection or phlebotomy therapy. Every pint of blood removed contains 250mg of iron. The body then uses some haemochromatosis of the excess stored tissue iron to make new blood cells which are removed in subsequent phlebotomy.

The length of treatment depends on the amount of excess iron in the body at the time of diagnosis, which is measured by the ferritin and transferrin saturation. Treatment may mean weekly phlebotomy for one to two years, or until the iron levels have been reduced to a safe level.

During the treatment the serum ferritin levels are monitored, the results of this test gives a measure of the remaining iron stores. Once the initial treatment is completed and the iron levels are back to normal then they are monitored every three months. As they start to rise again phlebotomy is recommended.

Treatment for haemochromatosis is ongoing for life and may require blood to be removed once or twice yearly depending on how quickly the iron is reaccumulating. This is called maintenance therapy.

Venesection treatment will allow iron tissue to be mobilised and iron stores will return to normal. However, it will not cure any clinical condition such as diabetes already present at the time treatment is started. This emphasises the importance of early diagnosis.

The common view is that a low iron diet is of little benefit and is not advised since considerably more iron can be removed in a single venesection.

The following is advised:

  • Modest alcohol consumption.
  • No iron medication or multivitamins containing iron.
  • No bread or cereals with fortified iron.

How is haemochromatosis inherited?

Inherited disorders are caused by defective genes in the cells which make up the body. Genes which are made up of DNA, contain the information the body needs to develop from the egg, and to maintain itself in good working order. Human beings have about 60,000 genes, and every cell in the body except the egg and sperm cell contain two copies of each. One of these copies is inherited from each parent.

The disease haemochromatosis is a recessive disorder. This means that it only develops if both copies of the gene are abnormal. If only one copy is defective an individual will be perfectly well but will be a carrier. About 20% of the population are carriers.

This means:

  • If both parents are carriers (about one in 25 couples). On average a quarter of the children will develop haemochromatosis, half will be carriers and a quarter will be normal.
  • If one parent has haemochromatosis and the other is a carrier (about 1 in 3,000 couples) on average half of the children will develop haemochromatosis and the other half will be carriers.
  • If both parents suffer from haemochromatosis, (a rare event, occurring in about 1 in 10,000 couples) all the children will inherit two defective genes and all will have haemochromatosis.
  • It should be emphasised that the proportions given in examples 1 and 2 are averages for the whole population. For instance, in any particular family where both parents are carriers, it would be possible for all children to be affected, all to be carriers, or all to be normal.

Who should be tested?

Relatives who are at risk should be tested. This is absolutely essential in the case of brothers and sisters (siblings) as they stand at least one in four chance of being affected. early detection and treatment will prevent all the complications of the disease.

Since the carrier rate is one in five, it is worth while screening the spouse of homozygotes.

Note that screening leads to early diagnosis and treatment, preventing complications developing from this frequent and potentially fatal genetic disorder.

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