The Genetics Of Hereditary Hemochromatosis
DEAR DR ROACH: I have hereditary hemochromatosis. I know that means that I received the HH gene from both parents; however, neither of my parents had HH. As I learn more about this very common genetic condition, I am wondering if my maternal grandfather, who died from colon cancer at a young age, and my paternal grandmother, who died from liver cancer, could both have had HH.
Could you please explain how this disease is inherited? – J.H.
ANSWER: Hereditary hemochromatosis is a condition where too much iron is absorbed, causing it to build up in the body. Without treatment, it can lead to damage to many organs, including the heart, liver and bone marrow. The genetics of hereditary hemochromatosis is called an autosomal recessive, meaning you need to have a copy of the gene from each parent in order to get the disease. It’s certain in your case that since neither parent has the condition, both of your parents were carriers of the disease, meaning each only had one copy of the gene. The chances of both of them passing on the gene to each child is one in four. However, many more people than you would expect are in your situation, since without a known family history of the condition, you wouldn’t have been screened for it and would have to wait for symptoms in order to get a diagnosis.
Unfortunately, symptoms of hemochromatosis can be vague and difficult for doctors to recognize. Even though it is the most common genetic disease in Caucasians (about 10 percent of Caucasians are carriers, higher in some populations), many doctors haven’t recognized a case. Fatigue, joint pain and loss of libido are the most common early symptoms. However, these are so common that they can be overlooked by both patients and doctors.
A good screening test is to look at the ratio of iron and “iron-binding capacity” levels in the blood. A level over 60 percent (50 percent in women) is 95 percent accurate to make the diagnosis, which would be confirmed with a liver biopsy or a genetic test. Family members of affected individuals should get tested by an expert in the condition.
DEAR DR. ROACH: I have had episodes for many years where I am shocked, like an electric shock, which wakes me from sleep. I jump out of bed, then my legs and feet tremble rapidly, and I need to sit down or I will fall. I have been diagnosed as having “night terrors,” but it is not that. I had a normal MRI.
It used to happen twice a week, then dwindled to monthly. Lately, I have it pretty much under control. I wonder if there is some diagnosis out there for me. I hope you have an answer. It would make me feel like less of an idiot! – J.N.
ANSWER: I don’t think you are an idiot at all, and I do think I know the cause of these episodes. You have a pretty severe case of nocturnal myoclonus (which sounds like I know what I am talking about, but it just means muscle jerks at nighttime). These are very common and usually are normal, but are sometimes associated with epilepsy. Since yours aren’t getting worse over time and you haven’t had seizures, you are almost certain to have the “physiologic” type. Occasionally, there is a family history. I don’t think you will need any treatment.
READERS: Heart disease remains the No. 1 killer. The booklet on clogged heart arteries explains why they happen and what can be done to prevent clogging. Readers can obtain a copy by writing: Dr. Roach – No. 101, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.
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