During your next game of medical trivia, Consumer Reports’ chief medical adviser, Marvin M. Lipman, suggests that you ask this question: “What’s the most common genetic disease of white men?” If all you do is draw blank stares, you can provide these clinical vignettes as clues:
●An apparently healthy 50-year-old man whose father, a nondrinker, died of cirrhosis of the liver.
●A 45-year-old man with severe heart failure whose coronary arteries are clear and heart valves are normal.
●A 57-year-old man with new-onset diabetes and a year-round tan who seldom exposes himself to the sun.
The answer: hemochromatosis. And in case that leaves the people you’ve stumped with only a quizzical look on their faces, you can add, “You know, iron-overload disease.”
Hemochromatosis was for many years thought to be a rare genetic disorder, Lipman notes. But today we know that it results from the inheritance of an abnormal recessive gene from each parent. Studies have found that one in every 150 to 250 white people is affected. It’s less common among blacks and practically nonexistent among Asians. The disease rarely shows up before people are in their 40s or 50s, and men are 24 times as likely to have complications from it as are women.
The defective gene causes decreased production of hepcidin, a liver protein that prevents the intestinal absorption of excess dietary iron. Except for menstruating women, we ordinarily need very little iron in our diets to balance out our losses. Were it not for that hepcidin-mounted defense, we all would be at risk for iron overload just from dietary sources. And when too much iron is absorbed, it can infiltrate and eventually destroy almost every major organ in the body.
People who don’t make enough hepcidin have no such protection, yet only about 10 percent will ever develop symptoms, for reasons still not understood. And in those who do, not all organs are involved at the same time or to the same extent.
The liver is most commonly affected, with cirrhosis (scarring) and liver failure the ultimate result. About 6 percent of those with cirrhosis develop liver cancer. A timely liver transplant offers the only chance for survival.
To avoid the fate of his father, the first man described above is getting the standard treatment for hemochromatosis, which involves periodic phlebotomy (bloodletting) to get rid of some of the excess iron.
When the heart is affected, as in the second vignette, the result can be cardiomyopathy (the replacement of the heart muscle with scar tissue), heart block (a disorder that causes a slow heart rate) and other abnormal heart rhythms. The cardiomyopathy is often resistant to treatment, and a heart transplant might be the only solution.
Infiltration of the pancreas with iron can cause secondary diabetes. If iron is also deposited in the skin, causing a brownish coloration as in our third example, the condition is referred to as “bronze diabetes.” The endocrine system, including the pituitary gland, the thyroid and the testicles, suffers as well, with impotence and other deficiencies as the result.
The laboratory markers for hemochromatosis can be found in relatively inexpensive blood tests. Elevation of serum ferritin, the protein that stores iron, can be the best indicator of increased iron. If tests show that transferrin, the protein that transports iron through the bloodstream, is saturated with iron, that virtually clinches the diagnosis. Gene testing should also be done before a patient begins periodic phlebotomy for an indefinite period of time.
Despite the frequency of the disease, universal screening is not recommended. Experts disagree about who will and who won’t develop symptoms, and the large racial disparities in disease prevalence argue against screening everyone. But targeted screening of people with certain risk factors and symptoms makes good sense.
Ask your doctor about testing if you have one or more of the following:
●A family history of hemochromatosis.
●A close family member with “nonalcoholic” cirrhosis of the liver, cardiomyopathy or primary liver cancer.
●Unexplained abnormal liver-function tests.
●Cardiomyopathy, heart block or abnormal heart rhythms.
●Adult-onset diabetes mellitus that requires insulin treatment.
●Impotence traceable to an endocrine cause.
For further guidance, go to www.ConsumerReports.org/Health, where more detailed information, including CR’s ratings of prescription drugs, treatments, hospitals and healthy-living products, is available to subscribers.