By Shane Harrison
BBC NI Dublin correspondent
The month of March is a time when Irish people all over the world take pride in their blood ancestry and their heritage - culminating with St Patrick's Day.
But with that same blood, because of a "Celtic gene", people of Irish ancestry are much more likely than any other global group to suffer from a potentially fatal disorder called haemochromatosis.
In the overwhelming majority of cases, it is treatable
The condition means having too much iron in the blood.
It is estimated that one in five Irish people carry this gene and one in 86 will go on to develop haemochromatosis.
It is associated with both men and women aged more than 40.
Its symptoms include excessive tiredness, male impotence, liver enlargement, arthritis in the hand and tanning easily.
Researchers at the Mater Hospital's liver unit in Dublin first identified the strong link between the Celtic gene and the inherited disorder.
Nobody is sure about why or when the Celtic gene suddenly developed or mutated, but researchers at the hospital believe it happened 50 generations ago, about 900 AD.
Professor John Crowe from the Mater's Liver Unit says the spread of haemochromatosis "around the world is associated with the Irish Diaspora".
"So, the highest frequencies (outside Ireland) are found in eastern Australia, eastern United States, in Great Britain and then to a lesser extent in Scandinavia, northern Spain and northern Italy."
Elizabeth Cronin from south Dublin found out she had haemochromatosis after she went to her doctor complaining of constant exhaustion and a pain in her liver area.
Blood test results showed she had too much iron.
Like other sufferers she gets the excess iron out of their system by blood letting, removing the blood from her body.
It is estimated that one in five Irish people carry this gene
"I go in on a two-weekly basis to hospital. My iron levels are beginning to decrease and now I'm feeling more energetic," she says.
"I'm going back to the things I used to enjoy, like walking and playing a bit of tennis."
Doctors say the condition can be fatal, particularly if too much iron builds up around the heart.
But in the overwhelming majority of cases, it is treatable - though the earlier it is spotted, the better.
Medics also dismiss the notion that the historic Irish fondness for iron-rich cabbage and Guinness are related to the complaint.
With doctors becoming increasingly aware of the condition, they recommend that anyone who has symptoms - such as tiredness or arthritis in the hand - should maybe get a blood test.
After all, it may not be the fault of your lifestyle - and you can always blame it on the ancestors.