Haemochromatosis Australia - the Genetics of haemochromatosis

Genetics of Haemochromatosis

Genes contain the information the body needs to develop from the first cells to the grown adult body. There are about 300,000 genes in the body and research continues to map these genes and understand how they affect our health and well-being. Genes come in pairs that are formed with one from the father and one from the mother.

Inherited disorders are caused by specific genes that have changed, or mutated over centuries and have been passed down through generations. You have no choice in the genes you inherit.

The gene that controls haemochromatosis has been identified and is known as HFE.

While several different mutations to this gene have been discovered, there are two main mutations or faults that cause hereditary haemochromatosis. These are referred to as C282Y and H63D. The C282Y mutation is associated with most cases of hereditary haemochromatosis. The H63D mutation seems to have less impact as do the other much rarer types.

Autosomal Recessive Disorder

Haemochromatosis is a recessive gene disorder. That means for the condition to be passed on, both mother and father must have one copy of the abnormal HFE gene. About one in seven people have one abnormal HFE gene. They are referred to as a 'carrier' because they carry a gene which may cause their children to inherit the disorder. Carriers won't develop the condition themselves.

If two carriers have children, their child has:

  • a 50 per cent chance of inheriting one mutated HFE gene and becoming a carrier
  • a 25% chance of inheriting both mutated HFE genes and therefore being at risk of excess iron absorption and developing symptoms of haemochromatosis
  • a 25% chance of inheriting two normal genes.

Terms

Heterozygous: Having one copy of the abnormal HFE gene, for example C282Y or H63D – also known as a 'carrier'.

Homozygous: Two copies of the same gene abnormality, for example C282Y and C282Y.

Compound heterozygous: Having one C282Y and one H63D abnormal gene. Compound heterozygotes usually have a milder form of haemochromatosis.

How does this affect my family?

If you have been diagnosed with haemochromatosis, you should talk to your family and explain what it is all about. It is important they are tested. If the test is positive they will have the chance to take control of their condition and if the test is negative they will have the reassurance they don't need to worry.

It can be difficult to talk about these things and sometimes family members are reluctant to listen. Your doctor may be able to help you work out a plan to inform your family. Help and advice is also available through our INFO LINE 1300 019 028.

Non-HFE haemochromatosis

1 in 700 people with haemochromatosis have no mutation in the HFE gene. This is known as Non-HFE haemochromatosis and is due to mutations in other genes.

Next, read about the treatment of haemochromatosis here.