Testing for Haemochromatosis; what’s new?
Hereditary Haemochromatosis (HH) is thought to be one of the most common genetic diseases in people of northern European descent. Around one in 200 Caucasian Australian people have a genetic predisposition to this disease, with the incidence also the same in New Zealand. This year, World Haemochromatosis Week took place between 3-9 June, a worldwide campaign to raise awareness of this disorder which causes the body to absorb too much iron, leading to iron overload. We spoke with Dr Samuel Vasikaran to discuss this disease.
“Haemochromatosis is an autosomal recessive disorder of iron absorption, with progressively increasing tissue iron deposition and organ damage. Not all patients with detectable common genetic abnormalities may be symptomatic, but they remain at risk for cirrhosis and other end organ damage.
“HH is most commonly caused by mutations in a gene called HFE. The two main mutations causing HH are referred to as C282Y and H63D. The C282Y mutation is associated with most cases of HH, and those with the mutation are at risk of developing iron overload. However, it should be noted that many individuals with HFE mutations will not have clinical iron overload as disease penetrance is low,” said Dr Vasikaran."
Testing for haemochromotosis should be performed in patients with;
- clinical signs or symptoms suggestive of diseases associated with iron overload [such as lethargy, fatigue, unexplained chronic liver disease, cardiomyopathy, type 2 diabetes mellitus, male hypogonadism, increased skin hyperpigmentation, certain arthropathies and porphyria cutanea tarda], or
- laboratory findings such as unexplained liver function test abnormalities, a high serum ferritin or transferrin saturation, and
- in first- or second-degree relatives of those diagnosed with HH.
Haemochromatosis tends to be under-diagnosed and, in many cases, there are no symptoms, especially in children and young adults. When symptoms do arise, they are often vague and can be similar to those caused by a range of other illnesses. Early diagnosis and treatment can prevent complications and results in normal life expectancy. Professor John Olynyk, Professor of Translational Medicine at the School of Medical and Health Sciences, Edith Cowan University, explains the testing involved for haemochromotosis:
“The most common blood test used to diagnose haemochromotosis is measurement of serum iron studies, which includes serum transferrin saturation and ferritin. Recently we have also shown that you can identify people at high risk of hemochromatosis using information presented in the results of a full blood count. This is something that we have built into the GP health pathways here in WA. There are a range of other blood tests, including liver biochemistry, testing for diabetes – arthritis test which can also determine if clinical problems are due to hemochromatosis or whether they are just occurring coincidentally.
“Full blood counts are done routinely in Australia, there are about 12 million done every year. Out of these blood counts that are being done often, if the results for Haemoglobin, white cell count and platelet count are normal – people tend to ignore the remaining parameters. However, if you pay attention to the mean cell volume (MCV) and mean cell haemoglobin (MCH), you can identify subgroups at substantially increased probability of having HH,” said Professor Olynyk
Professor Olynyk’s research team determined the sensitivity, specificity and clinical utility of erythrocyte parameters in 144 HH subjects with (n = 122) or without (n = 22) clinical and/or biochemical expression of iron overload. These results were compared with the general population and subgroups with chronic diseases. For both expressing and non-expressing HH subjects, the mean pre- and post-phlebotomy values of MCV and MCH were always significantly higher when compared to all other groups and demonstrated excellent diagnostic utility for detection of HH in men and women.
“What I now recommend in addition to the currently accepted guidelines for screening for HH is that those individuals of northern European ancestry with MCV greater than 94 fL or MCH greater than 32 pg also investigated for HH. If you are actually diagnosed early with the condition, before you have any end organ damage, then your survival and longevity is identical to everyone else of similar age and gender in our population. It is a completely treatable and controllable situation,” said Professor Olynyk.
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This article appeared in the June 2019 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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