A disease that was once thought to be the most common genetic disorder of Europeans has now been shown by scientists at The Scripps Research Institute (TSRI) to be relatively rare.
In what was one of the largest DNA-based genetic epidemiological studies ever conducted, TSRI researchers working with the Health Appraisal Clinic at Kaiser-Permanente in San Diego examined the DNA and clinical data of some 41,000 patients, looking for the genetic disease hereditary hemochromatosis, a metabolic disorder in which excessive amounts of iron are deposited in the liver, pancreas, and other organs. Hereditary hemochromatosis can lead to cirrhosis of the liver, diabetes, and cardiovascular disease, and the severe form of the disease can be lethal.
Although the mutation that causes hereditary hemochromatosis is common, the disease itself is rare, concludes study leader Ernest Beutler, M.D., who is Chairman of TSRI's Department of Molecular and Experimental Medicine and Professor, The Skaggs Institute for Chemical Biology. Even people with two copies of the genetic mutation that causes the disease hereditary hemochromatosis (so-called homozygotes) are very unlikely to become ill from it, the study finds.
A modest number of homozygotes do show minor abnormalities of liver function, but no symptoms. Most importantly, no difference was found in the life span of persons homozygous for the gene and those who do not carry it. The percentage of homozygotes in old people was the same as the percentage in young people, indicating that there is no attrition of homozygotes from the population. Presumably, other factors in addition to the gene mutation are required to cause the actual disease.
Beutler and his colleagues are careful to point out that it is very important to diagnose promptly those few patients who are severely affected because they can be treated quite simply and effectively by removing iron from the body by frequently drawing blood, as in
Contact: Robin B. Goldsmith
Scripps Research Institute