Q. I have hemochromatosis, as do several other members of my family. We regularly have blood removed to lower the amount of iron in our bodies. The sad part of this disease is that most people never know they have it, until it is too late. I'm writing in hopes of making more people aware of this potentially devastating hereditary disease.

A. You're right, most people don't know they have it. Fortunately, a simple blood test usually signals the presence of this slowly progressive disease. It also can detect affected family members who can get treatment before damage to the body's vital organs becomes irreversible.

The term hemochromatosis refers to an abnormal skin color originally thought to indicate excess iron in the blood. (Hemo means blood, chromo means color and osis means an abnormal condition). We now know that the excess iron actually comes from increased absorption of this essential nutrient in the intestines.

HC has two types, a hereditary form and one that develops later in life. The hereditary form results from an abnormal gene that makes the body absorb too much iron from the diet. In the less common acquired form, a build-up of iron results from some other disease. For example, people with sickle cell anemia who get many blood transfusions over the years can accumulate excess iron in their body. Another example is thalassemia, a type of hereditary anemia that can lead to iron overload. For some reason, people who drink a lot of alcohol are also prone to develop iron damage in their liver.

Although iron is essential for life, too much iron acts as a poison. Oddly enough, the body doesn't have any good way of getting rid of excess amounts. Because women tend to lose blood (and iron) with menstruation and pregnancies, they don't develop HC as often as men. Men are five to 10 times more likely to develop this disease, which usually first causes symptoms between the ages of 40 and 60.

HC is more common in whites than in blacks. About one in 10 white people carries the abnormal HC gene. These carriers have few if any symptoms. But about one in 200 will inherit the disease with all its potential complications.

The iron poisoning of HC attacks the liver, skin, pancreas, joints, heart and other parts of the body. Liver damage leads to an enlarged liver and ultimately cirrhosis -- a scarred, poorly working liver. Liver cirrhosis can be fatal in itself, but about one in three people will also develop rapidly fatal liver cancer.

The excess iron darkens the skin, giving it a bronze or metallic gray color. The pancreas is the gland of digestion that also makes insulin. Damage to this organ leads to lack of insulin and a resulting case of diabetes and high blood sugar.

Iron toxicity causes joint pain; too much iron in the heart muscle can lead to heart failure. In men, HC can impair their ability to have intercourse and cause impotence.

Your doctor may not immediately think of HC as an explanation for one of its many possible symptoms. However, once suspected, it is usually easy to diagnose. A blood test will show high levels of iron or ferritin, an iron-carrying protein. A liver biopsy will confirm the diagnosis.

Because HC can run in families, it's important that all close relatives be tested once one member shows up with the disease. Early treatment will prevent most serious complications, including liver cancer. Treatment is simple and consists of periodic removal of a pint of your blood. In fact, you can safely donate this blood and help others while helping yourself. This treatment extends the life of people with HC and prevents problems from developing in those with mild cases.

As for the acquired form, it's important not to take large doses of iron over a long period of time unless prescribed by your doctor. If you have a medical condition that requires multiple blood transfusions over the years, be sure you get only those transfusions that are necessary for your treatment. You can also get checked for early signs of excess iron in your body.

For more information, contact the Iron Overload Diseases Association Inc., 433 Westwind Dr., North Palm Beach, Fla. 33408 (407-840-8512) or the Hemochromatosis Research Foundation, P.O. Box 8569, Albany, N.Y. 12208 (518-489-0972).