Hemochromatosis, also called hereditary hemochromatosis, is a type of genetic iron overload disease caused by a gene change, also called a gene mutation. The gene change is passed down in families. This is by far the most common type of iron overload disease.
Other types of iron overload are not genetic. They may be called secondary iron overload or acquired iron overload.
Genetic causes of hemochromatosis
Hereditary hemochromatosis can be caused by mutations to different genes that control the amount of iron the body absorbs from food.
-
HFE gene.
A gene called
HFE
is most often the cause of hereditary hemochromatosis. This is the type of hemochromatosis that mostly affects adults in midlife. The
HFE
gene has two common mutations,
C282Y
and
H63D.
-
HJV,
HAMP
or
TFR2 genes. A mutation in any of these genes can cause a type of hemochromatosis called juvenile hemochromatosis. Juvenile hemochromatosis affects young people. It causes the same symptoms that hereditary hemochromatosis causes adults. But iron buildup begins earlier, so symptoms usually appear between the ages of 15 and 30.
If you inherit one gene mutation from each parent, you may develop hemochromatosis. You also can pass the altered gene on to your children. But not everyone who inherits two mutated genes develops symptoms linked to the iron overload of hemochromatosis.
If you inherit a gene mutation from one parent, you're not likely to develop hemochromatosis. But you are considered a carrier and can pass the altered gene on to your children. Your children won't develop the disease unless they also inherited another altered gene from the other parent.
Causes of secondary or acquired iron overload
Some iron overload is not caused by a gene change passed on in families. Examples include the following:
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Neonatal hemochromatosis is a serious disease where iron builds up quickly in the liver of a baby while in the womb. It is thought to be an autoimmune disease, in which the body attacks itself.
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Secondary iron overload can be caused by another condition that causes the intestines to absorb too much iron, such as liver disease, or by too much alcohol. Or it can be caused by too much iron in the body, such as from too many blood transfusions to treat anemia or other conditions. Less often, secondary iron overload can happen from taking too much of an iron supplement.
Diet alone usually does not cause iron overload. But, rarely, some people of African and African American descent may be at increased risk from a diet too high in iron. This is likely due to a gene change passed down in families.
How iron overload affects the organs
Iron plays an important role in several body functions, including helping to produce blood. But too much iron is toxic.
A hormone secreted by the liver, called hepcidin, controls how iron is used and absorbed in the body. It also controls how excess iron is stored in various organs. In hemochromatosis, the role of hepcidin is affected, causing the body to absorb more iron than it needs.
In other iron overload disease, the body does not absorb too much iron from food. Instead, it usually happens from too many blood transfusions.
In hemochromatosis and other iron overload disease, excess iron is stored in major organs, especially the liver. Over a period of years, the stored iron can cause severe damage that may lead to organ failure. It also can lead to long-lasting diseases, such as cirrhosis, diabetes and heart failure. Many people have gene changes that cause hemochromatosis. However, not everyone develops iron overload to a degree that causes tissue and organ damage.