Iron build-up in haemochromatosis

People with haemochromatosis are unable to adequately control the amount of iron they absorb. Typically they take in more than 30% of the iron in their food rather than the normal 10% or less. Iron absorption from the gut is governed by a series of genes that allow different amounts of iron to be absorbed, depending on whether the body needs iron or not. However, in haemochromatosis, these pathways are basically always switched on.

This means that the amount of iron absorbed greatly outstrips the amount of iron used, leading to an excess, which cannot be eliminated by the body. Total body iron levels build up gradually; men tend to show symptoms from about the age of 40 but women tend to be in their 50s as menstruation removes some of the excess iron.

Over a period of years the symptoms get worse and, if untreated, haemochromatosis can eventually prove fatal.

Fortunately, haemochromatosis can be diagnosed and treated effectively. If treatment is started before any significant organ damage has been sustained, life expectancy and life quality is likely to be normal. Types of haemochromatosis

There are two forms of haemochromatosis:

• Hereditary or primary haemochromatosis is by far the most common form
• Secondary haemochromatosis can be caused by blood disorders that result in large numbers of abnormal red blood cells being broken down. This can happen, for example, in haemolytic anaemia and thalassaemia major.

More rarely, excess iron levels can also be due to:

• Chronic liver diseases such as hepatitis C
• Alcoholism: damage to the liver can cause symptoms of iron overload to develop
• Kidney dialysis

Acaeruloplasminaemia or atransferrinaemia and some rarer genetic red blood cell disorders.

Excessive iron intake from iron supplements, injections or drinking beer brewed in iron containers. This is more likely in someone who also has a very high intake of vitamin C, which increases iron absorption.

The gene implicated in hereditary haemochromatosis

The gene most commonly associated with haemochromatosis is the HFE gene on the short arm of chromosome 6. The HFE gene codes for a protein that sits in the cell membrane of cells lining the digestive tract and regulates the amount of iron that is absorbed from the intestine. A defective gene codes for a protein that allows too much iron through.

A child that inherits two defective HFE genes, one from each parent, tends to develop haemochromatosis as an adult. A child that inherits one defective HFE gene only can pass it on to their children but may not develop symptoms. However, some adults with a single defective HFE gene do absorb slightly more iron than normal from their diet but their symptoms are not as severe as someone who carries 2 defective HFE genes.

Symptoms and complications of haemochromatosis

The liver normally stores the small quantities of iron that are needed to build new red blood cells, and it bears the brunt of iron overload. However, excess iron is also stored in the pancreas, the joints, the heart, the brain (an area called the basal ganglia) and in the endocrine glands.

The symptoms of haemochromatosis are caused by the effects of iron overload in these organs and include:

• Pain in the abdomen and joints
• Chronic tiredness and weakness
• Darker skin colour, known as bronzing, and loss of body hair
• Lack of sexual desire, impotence in men and lighter or absent periods or early menopause in women
• Confusion, depression and mood swings

Not everyone with haemochromatosis has symptoms and the severity of symptoms in those that do can vary unpredictably.

If untreated, haemochromatosis can lead to cirrhosis of the liver, which can result in liver cancer and liver failure. Build-up of iron deposits in the other organs can cause diabetes (if the pancreas is affected) and heart failure (if iron deposits form in the heart muscle).