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Causes
By Mayo Clinic staffIron plays an essential role in several body functions, including helping with the formation of blood. Most people absorb about 10 percent of the iron they ingest. When these stores are adequate, the body reduces the amount of iron absorbed by the intestine to avoid accumulating excess amounts.
But if you have hereditary hemochromatosis, you may absorb as much as 30 percent of the iron you ingest. Because your body can't use or eliminate this extra iron, it's stored in the tissues of major organs, especially your liver. Eventually you may accumulate five to 20 times as much iron as normal. Over a period of years, the stored iron can severely damage many organs, leading to organ failure and chronic diseases such as cirrhosis and diabetes.
The genetics of hemochromatosis
Genes are information centers in your cells that control your body's growth, development and function. A mutation in just one gene can drastically alter the way your body works.
The gene that controls the amount of iron you absorb from food is called HFE. The HFE gene has two common mutations, C282Y and H63D. In the United States, most people with hemochromatosis have inherited two copies of C282Y — one from each parent.
Inheriting just one gene with the C282Y mutation means you're a carrier. You aren't likely to develop the disease yourself, although you may absorb more iron than normal. About one in every 10 Caucasians carries one gene for hemochromatosis. If both your parents are carriers, you have a 25 percent chance of inheriting two mutated genes. Complicating things is the fact that not everyone with two copies of C282Y will experience symptoms.
A few people inherit one copy of C282Y and one of H63D. Of these, a small number develop symptoms of hemochromatosis. An even smaller number of people inherit two copies of H63D. Whether they're at risk of hereditary hemochromatosis is a matter of debate.
Other types of hemochromatosis
Other forms of hemochromatosis include:
- Juvenile hemochromatosis. This causes the same problems in young people that hereditary hemochromatosis causes in adults. But iron accumulation begins much earlier and symptoms usually appear between the ages of 15 and 30. Common complications include diabetes and problems with sexual development — which may lead to impotence, amenorrhea and infertility. Complications may also include an irregular heartbeat (heart arrhythmia) and heart failure — a condition in which your heart can't circulate enough blood to meet your body's needs. When not treated, juvenile hemochromatosis can be fatal. Although juvenile hemochromatosis is an inherited disease, the genetic abnormalities that cause it don't involve the HFE gene. Instead, it's caused by a mutation in a gene called hemojuvelin.
- Neonatal hemochromatosis. In this severe disorder, iron builds up in a baby's liver so rapidly that he or she may be stillborn or die within a few days of birth. Just what causes neonatal hemochromatosis isn't known.
