Testing for inherited iron overload
We spoke to Dr Kym Mina, Director of Genetics at Douglass Hanly Moir Pathology, earlier this month during Haemochromatosis Awareness Week (4-10 June 2018) to find out about inherited iron overload.
“Hereditary haemochromatosis is a disorder which causes the body to absorb too much iron from the diet. If we take in too much iron, the body doesn’t have a way of increasing the amount of iron that it removes and therefore we accumulate iron in our tissues and organs and this can cause damage to those organs.”
Inherited disorders are caused by specific genes that have changed or mutated and been passed down through generations. While several mutations to the gene that governs iron absorption have been discovered, C282Y and H63D are the two main mutations that cause hereditary haemochromatosis.
"Haemochromatosis is most commonly caused by the C282Y mutation in a gene called HFE. Those with the mutation are at risk of developing iron overload. It is estimated that 1 in 200 Caucasians are homozygous (have two copies of the same gene abnormality) for that mutation."
For the condition to be passed on, mother and father must each have one copy of the abnormal HFE gene.
“Whilst there might be 1 in 200 people who are homozygous for that mutation, not everybody that has the mutation will actually develop iron overload and clinical features of haemochromatosis. It’s estimated that in females about 1% of those with the mutation will actually develop clinical features, although it’s higher for males (about 28%), so men are more commonly affected than women by this disorder,” says Dr Mina.
“Haemochromatosis caused by the C282Y mutation is an adult onset disorder, so you might expect to see it in males between the ages of 40 and 60 years of age. Typically, it is seen in females after menopause, which is due to the fact that they stop menstruating so they’re no longer losing iron in that way.”
Chronic fatigue and joint pain are the most common complaints of people with haemochromatosis. Patients often complain of lack of energy, abdominal pain, memory fog, loss of sex drive, heart flutters and irregular heartbeat.
“Early symptoms can be non-specific but, as iron accumulates in tissues, individuals may begin to experience joint pain and stiffness. A serious consequence that we associate with haemochromatosis is liver cirrhosis, which is fibrosis and scarring of the liver. Other major features we see include diabetes, heart abnormalities and skin discolouration. Whether these features develop is also affected by environmental factors, for example alcohol consumption increases the load on the liver and therefore the risk of developing cirrhosis,” explains Dr Mina.
“Pathology plays a critical role in the diagnosis of haemochromatosis. It’s detected by laboratory iron studies, in particular by ferritin and transferrin levels. This provides us with a measure of how much iron you have in your body. If the levels of those are high, this might alert your doctor to the fact that you may be iron overloaded. From there, a number of tests can be done, including a DNA test to look for the C282Y mutation in the HFE gene to see if the iron overload is genetically caused, or if it is a result of other non-genetic causes.
“Many people who have the mutation don’t ever require treatment because they don’t go on to develop iron overload. However, for those who do develop overload, the recommended treatment is therapeutic blood donation. This involves a schedule of blood donation and, during the course of that, iron levels are monitored. Once iron returns to a normal level, some patients can stop donating blood, but most will need to continue to do so less frequently.
“Genetic testing is recommended for anyone who has repeatedly elevated iron levels, or a first degree blood relative that has haemochromatosis or is known to have the mutation. Testing is available on Medicare under those circumstances.
"It’s very important to diagnose someone who has hereditary haemochromatosis early because you can prevent some of the end organ damage caused by iron accumulation. Once a patient has developed cirrhosis, they are then at risk of other complications, including liver cancer and complete liver failure, so it’s better to identify these people before that kind of damage occurs. Pathology and genetic testing play a key role,” says Dr Mina.
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This article appeared in the June 2018 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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