Hereditary hemochromatosis (HH) is a genetic disease that alters the body's ability to regulate iron absorption. If correctly diagnosed, HH is easily and effectively treated, but if untreated, it can lead to severe organ damage. Caucasians of northern European descent are at highest risk. An estimated one million people in the United States have hereditary hemochromatosis.
HH causes the body to absorb too much iron. Normally humans extract needed iron from food via the intestines. When there is an adequate amount of iron, the body reduces its absorption to avoid excessive accumulations. In a person with HH, the mechanism for regulating iron absorption is faulty and the body absorbs too much iron.
Over time - several years - this excess iron is deposited in the cells of the liver, heart, pancreas, joints and pituitary gland, leading to diseases such as cirrhosis of the liver, liver cancer, diabetes, heart disease and joint disease.
The gene that causes hereditary hemochromatosis, called HFE, was identified on chromosome 6 in 1996. Most cases of HH result from a common mutation in this gene, known as C282Y. But other mutations that cause this disease have also been identified, including one known as H63D.
A child who inherits two copies of a mutated gene (one from each parent) is highly likely to develop the disease. However, not all people who have two mutated copies develop signs and symptoms of HH.
People who inherit only one copy of the mutated gene are carriers, but usually have no symptoms, or have very mild symptoms since one correct copy of the gene appears to adequately regulate iron absorption. "Silent" carriers, without symptoms of the disease, can still pass on the defect to their children
If two parents are silent carriers, each child has a 25 percent chance of inheriting two copies of the defective gene, and will most likely develop the disease. An estimated 10 percent of the U.S. population carries the gene. Carriers are most likely to exhibit signs of the disease if there are triggers such as diabetes or alcoholism.
Hemochromatosis is one of the few genetic diseases for which there is a relatively simple and effective therapy. The disease is treated by removing blood (known as phlebotomy) from the patient in order to lower the overall level of iron in the blood.
Initially, the patient undergoes phlebotomy frequently to lower the level of iron. After this initial phase, phlebotomies are performed only as needed to keep iron levels normal. When phlebotomy is started early in the course of the illness, it can prevent most complications. But even if phlebotomy is begun after complications have occurred, the treatment can still decrease symptoms and improve life expectancy.
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While there are laboratory and gene tests for HH, the disease is still difficult to diagnosis. The symptoms of HH are numerous and similar to other common diseases such as diabetes, heart failure, arthritis, liver disease, impotence and depression.
If hemochromatosis is suspected, patients are most frequently given a blood test to measure transferrin saturation. Transferrin is a protein that transports iron in the blood, and high transferrin saturation may indicate hemochromatosis. But it is not a foolproof diagnosis - individuals with high saturation levels may not have the disease.
Gene testing can be used to confirm a diagnosis of hemochromatosis. There are two gene tests: the cheek test and the whole blood test. The cheek test uses a mascara-like wand to scrape cells from the inside of the mouth. For a whole blood test, a vial of blood is drawn from the arm. Both of these tests are about 85 percent accurate. They may miss people who have the disease and identify people with two copies of the mutant genes who may never develop the disease.
Genetic testing is considered useful for couples planning to have a family. The test can identify carriers who may pass on the mutation to their children. Two carriers who never manifest symptoms can have children who inherit the defect and develop the disease. Since early diagnosis means early treatment and effective disease management, there may be benefits in identifying children at risk.
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Currently, NHGRI is not conducting research on Hereditary Hemochromatosis.
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Last Updated: October 23, 2012