What is Hemochromatosis?
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What is Hemochromatosis?

It's the most common genetic disease in individuals of European ancestry. 1 in 9 is a carrier

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Hereditary Hemochromatosis is a genetic disorder that causes the body to absorb and store too much iron. The excess iron builds up in the body's organs over time and eventually leads to organ damage. If hemochromatosis is not detected and treated early, it may eventually cause serious irreversible disorders such as arthritis, liver disease, heart disease and diabetes later in life.

Too Much Iron

Iron is an essential nutrient that is found in many foods. Iron is found in highest levels in red meat, iron-fortified breads, and cereals. Our body requires iron to make hemoglobin, a component of blood that is responsible for transporting oxygen from the lungs to all of the tissues of the body.

While too little iron can lead to anemia, too much iron can cause irreversible organ damage, eventually leading to disease and early death.

Normally, people absorb approximately 10% of the iron contained in the food that they eat. However, people with hemochromatosis absorb approximately 30% of the iron. Since the body cannot excrete excess iron, the extra iron is absorbed and retained in the organs of their body and builds up during their lifetime, particularly the liver, heart and pancreas, causing a number of serious diseases late in life.

What Causes Hereditary Hemochromatosis?

Hereditary hemochromatosis is caused by defects in a gene called HFE. The HFE gene is responsible for regulating the amount of iron that is absorbed from the food that we eat. There are three known mutations which cause the HFE gene to become defective: C282Y, H63D and S65C.

Genetics of Hemochromatosis

We all have two copies of the HFE gene, one copy inherited from our mother and one copy inherited from our father. Our chances for developing hemochromatosis depends on whether we have inherited the normal or the defective HFE gene from our parents.

Hereditary hemochromatosis can occur when a person inherits two defective copies of the HFE gene, one from each parent. Men and women have the same chance of inheriting two copies of the defective HFE gene.

A person who has inherited one defective HFE gene and one normal HFE gene usually does not develop the symptoms of hemochromatosis, as the normal gene can balance out the defective HFE gene. In a small number of cases, inheriting only one defective gene may still eventually lead to iron overload, possibly affecting the heart. In these people, the iron overload may be triggered by a precipitating factor, such as hepatitis (inflammation of the liver) or alcohol abuse.

How Common is Hemochromatosis?

Hemochromatosis is one of the most common genetic disorders in individuals of European ancestry. While this disease affects other ethnic groups, the groups at highest risk are Caucasians of Northern European descent.

Statistics

Approximately 1 out of every 9 individuals of European ancestry carries at least one copy of the defective gene for hemochromatosis. Individuals with one copy of the defective gene have a 50% chance of passing the defective gene to the next generation.

Approximately 1 out of every 200 individuals of European ancestry carries two copies of the defective gene for hemochromatosis and is at risk of being affected by the disease. Individuals with two copies of the same defective gene have a 100% chance of passing the defective gene to the next generation.

Although both men and women can inherit the gene defect, men are more likely than women to be diagnosed with hereditary hemochromatosis at a younger age. On average, men develop symptoms and are diagnosed between 30 to 50 years of age. For women, the average age of diagnosis is about 50.

Ethnic Background Risk

People of Northern European descent are more prone to hereditary hemochromatosis than people from other ethnic backgrounds. Most at risk for hereditary hemochromatosis:

  • British
  • Scottish
  • Irish
  • Dutch
  • Danish
  • Scandinavian
  • German
  • French
  • Spanish (Northern regions)
  • Italians (Northern regions)

Hemochromatosis is less common in Africans, Asians, Hispanics/Latinos, and American Indians.

Family History

Also at risk are people with a blood relative who has been diagnosed with hemochromatosis.

A person's family history can offer clues about the chances of being affected hemochromatosis. DNA testing for hemochromatosis should be performed on anyone with a family history of any of the following:

  • a premature death by heart disease (heart attack, congestive heart failure) or liver disease (cirrhosis, liver cancer)
  • diabetes mellitus
  • skin color changes - bronze colored skin
  • osteoarthritis or complaint of joint pain
  • hypothyroidism
  • infertility
  • impotence
  • depression

Other Known Types of Hemochromatosis

While Hereditary Hemochromatosis is the most common type of hemochromatosis, several other rarer forms of hemochromatosis which are not caused by a defective HFE gene also exist that are not discussed in this website. The other known types of hemochromatosis are:

Juvenile Hemochromatosis (aka Type 2 Hemochromatosis)

This type of hemochromatosis leads to severe iron overload and liver and heart disease in adolescents and young adults between the ages of 15 and 30. Common symptoms and complications include diabetes, problems with sexual development, impotence, infertility, irregular heartbeat and heart failure. If not detected and treated early, juvenile hemochromatosis can be fatal. This disease is caused by a mutation in a gene called hemojuvelin (HJV or HAMP gene).

Neonatal Hemochromatosis

This type of hemochromatosis causes rapid iron buildup in a baby's liver that can lead to stillbirth or death within a few days of birth. The cause of this disease is currently unknown.

TFR2-Related Hereditary Hemochromatosis

Age of onset is earlier than in HFE-associated HHC. It is caused by mutations in the TFR2 gene

Type 4 Hemochromatosis

Caused by mutations in the SLC40A1 gene.