Study Finds Vulnerability Among African-Americans, Caucasians; May Help Create More Effective Screening for Hemochromatosis
Irvine, Calif., Oct. 8, 2001 -- A genetic disorder that causes iron overload is surprisingly prevalent among Caucasians and African-Americans, according to a study led by a UC Irvine College of Medicine research team.
The study, conducted from data on about 30,000 people provided by the National Institutes of Health, confirms that a significant percentage of Caucasian and African-American men and women have a risk of iron overload disorder. The study also may help scientists develop more effective ways to screen people for the disease. The researchers' findings will appear in the Oct. 15 issue of the journal Blood.
Iron overload disorder, also known as hemochromatosis, is considered one of the most common genetic disorders. Most people who carry the gene for hemochromatosis don't know it. But children of two adult carriers of the gene do get the disease, which affects about 1.5 million people nationwide. If left untreated, hemochromatosis can cause diabetes, arthritis, congestive heart failure, cirrhosis of the liver or liver cancer. There is no cure, but early screening usually leads to effective treatment that prevents complications of the disease.
Scientists have assumed the disorder occurs most often among Caucasian men. Christine McLaren, professor of epidemiology at UCI, Dr. Gordon McLaren, professor of hematology and oncology at UCI and a physician at the U.S. Department of Veterans Affairs Long Beach Healthcare System, and colleagues found a small but significant percentage of Caucasians and African-Americans who have more iron overload than researchers had previously assumed. The findings indicate that additional, unknown genes contribute to iron overload but also point to ways to screen people for the disease more effectively. The researchers used data from the NIH's National Health and Nutrition Examination Survey, which was conducted between 1988 and 1994 by the National Center for Health Statistics.
"In this study, we found subgroups of people who were more at risk than others of developing hemochromatosis," Christine McLaren said. "Most important, we found that although African-American men and women and Caucasian women have overall lower risks of getting hemochromatosis, a significant percentage of them show very high levels of either iron transport or storage, indicating their vulnerability to the disease. These findings also helped us determine certain chemical markers in blood we can measure, so we may be able to develop a more effective way to screen the entire population for their susceptibility."
The study also indicated that African-Americans may have an unknown genetic mutation that leads to iron-overload disorder. This mutation is different from the genetic mutation that occurs among Caucasian carriers and sufferers of the disease. Among the four groups studied, however--African-American men and women and Caucasian men and women--each of the groups had a small but significant percentage of people who were at risk.
The study also showed that screening for two important markers in the blood may be more effective for determining the risk of hemochromatosis. The researchers found the existence of the higher-risk subgroups by comparing not only a chemical called transferrin, which transports iron in the blood, but also a chemical called ferritin, which reflects the amount of iron stored in body tissues. Faulty genes cause the disease by increasing the absorption of iron and raising its levels in the body. If the two tests are used together, the research suggests that screening for the disease could be more effective.
"By comparing transferrin and ferritin, we identified these subgroups that are at risk for the disease," Gordon McLaren said. "This demonstrates that testing for both can be a more effective screening method. By identifying affected persons in this way, we may be able to find what other genes may be acting to produce hemochromatosis in these groups of people."
The McLarens and a national research team studying the disorder are enrolling volunteers to screen them for hemochromatosis and determine overall genetic influences on the disease. So far, they have screened more than 3,000 participants for the disease at the UCI trial site. People who would like more information about the study should call (714) 456-2050.
The McLarens' colleagues in the study include Kuo-Tung Li of UCI's Chao Family Comprehensive Cancer Center, Victor Gordeuk of Howard University and Victor Hasselblad of Duke University.
The researchers were supported by grants from the National Institutes of Health, the Department of Veterans Affairs and the National Center for Health Statistics.
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