Haemochromatosis is caused by a fault in a specific gene, known as HFE, which can be inherited from your parents. This faulty gene allows your body to absorb excess amounts of iron from food.

Normally, the body maintains a steady level of iron. The iron is absorbed from food and the amount absorbed varies according to the body's need for it.

People with haemochromatosis cannot control levels of iron in their bodies in this way. As a result, iron builds up over time and is usually deposited in the liver, pancreas, joints, heart or endocrine glands. 

Inheriting the HFE gene

Everyone receives two sets of genes – one from their father and one from their mother. If a person receives one set that includes the mutated HFE gene and one that does not, they won't develop symptoms but they will be a carrier of the HFE mutated gene.

In some ethnic groups, such as people of Irish descent, as many as one in 10 may be a carrier of the HFE mutation.

If a carrier of the mutated HFE gene mutation has a baby with another carrier there's a significant chance the baby will receive two sets of the HFE gene and develop haemochromatosis.

The likelihood of the child being affected is as follows:

• there is a one in four chance that the baby will receive a pair of normal HFE genes and be unaffected
• there is a one in two chance that the baby will receive one normal HFE gene and one mutated HFE gene – this means they will not have haemochromatosis but they will be a carrier of the condition
• there is a one in four chance that the baby will receive a pair of mutated HFE genes and possibly develop iron overload later in life

It's important to note that less than 10% of people who inherit two mutated genes (one from each parent) will actually develop symptoms and signs of iron overload.

The reason for this is not known but there are likely to be other genes inherited from each parent that influence whether the symptoms or signs appear. These genes are not currently identified so there is no genetic test available to identify who will go on to develop diabetes, liver, endocrine or heart disease.