ST. LOUIS---What is the most common genetic disorder in the United States? Many Americans would be surprised to learn it is hemochromatosis, a disease in which the body absorbs too much iron from the gastrointestinal tract. Hemochromatosis affects approximately one in 200 people in the United States and one in nine persons is a carrier. About 1.5 million Americans are unaware they have the disease.

July is "Hemochromatosis Screening Awareness Month," an ideal time to get tested for this common but highly treatable disease. The initial screening consists of a simple blood test to measure iron levels. "If it is diagnosed in time, those with the disease just need blood removed periodically to remove the excess iron from their system," said Bruce R. Bacon, M.D., director of the division of gastroenterology and hepatology at Saint Louis University School of Medicine. "A person with properly managed hemochromatosis who has no evident tissue or organ damage has as good of a chance of living a long, healthy life as someone who does not have iron overload."

We hear so often of iron's benefits to the body, but too much iron can have serious consequences. Normally, the body only absorbs as much iron as it needs. But in patients with hemochromatosis, excess iron is absorbed and stored throughout the body, in places such as the liver, pancreas and heart, and builds up to toxic levels, damaging these organs and tissues. Cirrhosis of the liver, liver cancer, diabetes, impotence and heart failure can be caused or worsened by hemochromatosis.

Hemochromatosis is sometimes called hereditary hemochromatosis or HH. It is caused by a mutation in a particular gene, the HFE gene, which is inherited from both parents. There can be several generations of silent carriers of the mutated gene who never become ill, which may give a false security that hemochromatosis does not "run in the family." Often, those who get the disease are of northern European descent, particularly those of Irish, Scottish or British heritage.

Women and men are equally likely to carry the gene for iron overload, but men are more likely to become sick from iron accumulation. "Menstrual bleeding provides some reduction of the excess iron," Dr. Bacon said. "However, after menopause, women become just as vulnerable as men to hemochromatosis."

The most common first symptoms are a vague feeling of fatigue or joint aches. Often these may be so mild they pass unnoticed. Impotence or loss of sexual desire may ensue; some women stop menstruating. Depression can also occur.

Dr. Bacon emphasizes, "Although some people may develop problems by age 20, symptoms usually do not appear until between 40 and 60 years of age. By then, the patient may have already sustained serious liver damage. That's why it's so important to get screened for this disease."