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The Frequency of Genes for Hemochromatosis in Patients Attending a Health Appraisal Clinic
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What is the problem and what is known about it so far?
Hereditary hemochromatosis is a genetic disease in which iron is deposited in body tissues. Iron deposits can lead to serious liver damage (cirrhosis), diabetes, heart failure, arthritis, and bronze discoloration of the skin. When hemochromatosis is detected early, organ damage can be prevented by routinely removing blood. Standard screening tests for hemochromatosis include blood tests that indicate body levels of iron. Recently, a test was developed for the HFE gene, the gene that is most commonly affected in hereditary hemochromatosis. Three different mutations are known to occur in this gene: C282Y, H63D, and 193T. The relationship between these mutations in the HFE gene and standard screening tests for body iron stores has not been well studied.
Why did the researchers do this particular study?
To determine the frequency of the mutations of the hemochromatosis gene in various ethnic groups and describe results of standard laboratory tests in persons with the mutations.
Who was studied?
The study included 10,198 adults who attended Kaiser Permanente's San Diego Health Appraisal Clinic. This clinic is available to all Kaiser Health Plan members who want a general health assessment. Study patients had to be older than 25 years of age and had to give consent to have their blood tested for the hemochromatosis gene.
How was the study done?
All study participants had a complete medical history, blood counts, and standard blood tests for transferrin saturation (one measure of body iron stores) and serum ferritin (a different measure of body iron). They were also studied for the presence of the three known mutations of the HFE gene.
What did the researchers find?
Among white people, approximately 12% had one copy of the C282Y mutation (out of a possible two copies), 30% had one copy of the H63D mutation, and 3.2% had one copy of the S63C mutation. The increase in transferrin saturation and ferritin levels in these people was minimal. Of 33 people who had two copies of the C282Y mutation, fewer than 50% had transferrin saturations greater than 50% (a commonly used cut-off value for the diagnosis of hemochromatosis). Half of the women and all but one of the men with two copies of the C282Y mutation had elevated serum ferritin levels. No person with two copies of that mutation had serious medical problems.
What were the limitations of the study?
People who are enrolled in the Kaiser Permanente health plan, wished to attend the health appraisal clinic, and consented to undergo gene testing may not be representative of the general U.S. population. The study does not tell us who went on to develop meaningful medical problems caused by the hemochromatosis that was detected by screening.
What are the implications of the study?
Determining transferrin saturation and ferritin levels will detect only about half of persons who have two copies of the C282Y mutation, because many of these persons have normal transferrin saturations and normal serum ferritin levels.
Article and Author Information
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The summary below is from the full report titled “The Effect of HFE Genotypes on Measurements of Iron Overload in Patients Attending a Health Appraisal Clinic.” It is in the 5 September 2000 issue of Annals of Internal Medicine (volume 133, pages 329-337). The authors are E Beutler, V Felitti, T Gelbart, and N Ho.
- Copyright ©2004 by the American College of Physicians
