Download IMPLICATIONS OF GENETIC TESTING ON HEMOCHROMATOSIS

IMPLICATIONS OF GENETIC TESTING ON HEMOCHROMATOSIS
Dr. Paul Adams
Some of you might be wondering why on earth we have such an esoteric topic on the topic list
today. But I think you’re going to see as my presentation unfolds that hemochromatosis is an
extremely common condition in Canada and in the U.S.; and that gene testing is here and in
many labs it’s the most common gene test done - that is, it’s being being done more commonly
than the tests for the breast cancer genes, colon cancer, cystic fibrosis, etc. In London, we’ve
done about 12 thousand gene tests, and we expect to do 20 thousand more gene tests this year.
The first slide is a picture of the ancient Celtic empire - Celtica. Some of you, when you think of
Celts, may think of men in skirts throwing logs; that’s actually a very limited view of the Celtic
empire, which extended over most of Northern and Central Europe. In fact, in my clinical
practice in which we have 395 hemochromatosis families that come to my clinic, most of them
come from the North of Portugal; the rest of them come from the United Kingdom and
Scandinavia. Virtually everyone that I’ve ever seen that had hemochromatosis has had ancestors
from this area.
How did the very first people get hemochromatosis? I’m not going to answer that question for
you. The company that found the gene for hemochromatosis in 1996 (and has since gone
bankrupt, I might add) estimated that the very first people with hemochromatosis were born in
the year 800 AD. This is an estimate obviously based on a pyramid going back through the
generations. For many years we’ve known that a so-called epicenter of hemochromatosis was
the very west of France – that area is known as Brittany, and that is where Jacques Cartier set
out from. There is a big plaque there laid down by Pierre Trudeau (your tax dollars at work),
and it’s quite tempting to think that the genes for hemochromatosis came to Canada from this
area. Now when the gene was first discovered in 1996, we had a very simple blood test that
could be done on stored samples. A number of groups went into their freezers and tested all
kinds of blood samples that had been stored for other reasons - PKU, and so on; this is exactly
what you’re not supposed to do, because you don’t have consent. Despite that, they found that a
very high prevalence for hemochromatosis was found in Iceland. The French did not go to
Iceland during their explorer days, but the Vikings did; and when you look at the Viking maps of
800 AD, they’re all over this part of France. So I’m speculating that the very first people with
hemochromatosis could have been a woman from this part of France and a Viking. You
probably know a big part of being a Viking was spreading your genes around.
And really now, the story of hemochromatosis is the story of Celtic migration. I’ve mentioned
to you the migration from this part of France over to Canada and the New World; similarly, the
British sent their prisoners to Australia, and there is a very high prevalence in Australia now of
hemochromatosis, and the British and the Dutch went to South Africa and in Caucasian people
in South Africa, it’s extremely common. You may not be as familiar with the fact that a group
from Wales went in the 19th century to a part of Argentina; the towns there still have ancient
names from Wales, and there’s a pocket of hemochromatosis there.
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Hemochromatosis has been very, very good for me too. I’ve been able to move all over the
world. I’ve worked on this disease in France, Australia, San Francisco, Manhattan. Really the
big news that prompts me coming to talk to you today is the discovery of the gene, and this
happened in 1996, and was a brute force biotechnology effort in California. We’d known for a
long time that the gene was on chromosome 6 because we used to use HLA typing as a surrogate
marker for the gene which is now obsolete. And a company marched down the gene until they
found an area that had some clue that it was an iron-linked gene; and this was called HFE. From
this discovery came a simple and inexpensive blood test that is widely used now today. But we
had been anticipating this in our lab for a long time; so finally, when it happened, we were left
with several of these common questions - now what?
Well perhaps the identification of the gene would lead to identification of the gene product
which would likely be a protein; and if we knew what the protein was, perhaps we could
understand the pathogenesis of this disease. How does it increase iron absorption? Perhaps, in
some cases, this leads to new therapeutic strategy. I think gene therapy is very unlikely for
hemochromatosis; we have a very old fashioned treatment, which is bleeding, which works very
well, and people have died from gene therapy. Using the gene test to screen within
hemochromatosis families; I think this is an excellent application, and would not be considered
controversial. Screening the general population is controversial and it’s something that we are
involved with right now - I’ll show you some data on that later on in the talk.
I didn’t think the audience would be that interested in the biochemistry of pathogenesis of
hemochromatosis, but one concept that I want to leave with you is that the abnormal HFE gene
in hemochromatosis creates an abnormal HFE protein - it’s all shrivelled up within the cell.
And this triggers a cascade of events with other genes and proteins that ends up with increased
iron absorption – involving a transferrin receptor, some very new genes and some export genes
here. If you remember the pathways involved in blood coagulation or complement activation, the
same kind of cascade event happens.
How common is hemochromatosis? In the old days, I used to start my talks by asking people in
the crowd how common they thought it was. We’d have estimates like 1 in 100 thousand or 1 in
500 thousand; and then I put up my slide that showed that it was 1 in 300. It was rather
embarrassing to the audience, and I found I didn’t get asked back very often. But some of you
might be quite startled to see that the prevalence of hemochromatosis in London, Ontario in a
big screening survey is 1 in 327. Now you might say well, there’s a lot of in-breeding in
London; in fact I’ve only met one patient who told me that the only girls that he met were at a
family reunion. And in fact, it’s mostly people from the States who say that to me, and now we
find that in Maine here it’s 1 in 143; in San Diego (in a large study that was published in the
Annals of Internal Medicine) 1 in 268; in Springfield, Missouri it was 1 in 276. These are
homozygotes, not carriers. And in the Celtic areas such as Dublin or Portugal, it’s 1 in 100. In
Dublin 1 in 4 people carry the hemochromatosis gene.
Well, before we touch on how you can make a diagnosis - sensitivity, specificity, etc… - you
have to have a case definition or gold standard; and this is clearly a problematic area in
hemochromatosis. Prior to the gene test, we used to define the disease as iron overload. So it
was no surprise that everybody that came under this diagnosis had an elevated transferrin
saturation and serum ferritin; those were used as part of the diagnostic criteria. In fact it was a
statistical flaw to talk about the ‘sensitivity’ of them as a screening test, because we used them
as part of the diagnosis. Many people had a biopsy of the liver and we graded the iron in the
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biopsy to determine whether they had cirrhosis; or if you were a hematologist you just took bags
of blood off and counted how many bags of blood it took to get them down to normal.
We’ve now got a gene test. The slide illustrates the C282Y mutation; this shows two copies,
one from the mother and one from the father. One of the very unusual things about
hemochromatosis is that this pattern at our centre explains 97% of cases - these were cases
diagnosed before we had the gene test. This is very atypical in genetic testing; if you think of
cystic fibrosis or Wilson’s disease, or alpha 1 antitrypsin deficiency, there are 50 or 60 different
mutations of the gene, which makes it complicated to do genetic testing. In hemochromatosis
we have one single mutation that explains nearly all the cases. A less common pattern is the socalled compound heterozygote; these individuals carry one of the C282Y mutations along with
a minor mutation called H63D. If we use this as the gold standard, we can then go back and see
how good transferrin saturation and ferritin were as diagnostic tests; and then there are some
surprises.
First we look at transferrin saturation among C282Y homozygotes; the normal range in our lab
would be 20% to 55 %, so say you did a cut off at 55%, all these cases here will be below the
line. This has big implications if you are talking about a population screening project. Similarly
for the compound heterozygote and the H63D homozygote. So people that have been referred to
my clinic for iron overload are the tip of the iceberg, and in fact when we do population
screening studies, we find that most people with these so-called minor or intermediate genotypes
have normal iron studies. Here’s the same thing with ferritin - again the upper range of normal
might be 300, may be a little lower in women; and if you drew a line across here, you’ll see
there’s lots of homozygotes who don’t have a high ferritin. To try and put this together we’ve
recently revisited Bayes’ theorem to predict who is going to be a C282Y homozygote. This is
unpublished data, where we plotted the ferritin on the left, transferrin saturation in the middle,
and created the probability of them being a homozygote using both tests (and this is based on
8,000 genotypes). You might say, well, why not just do the gene test?
What are the symptoms of hemochromatosis? I think it’s important when you’re giving a talk
like this to an audience to make everybody feel like they have hemochromatosis. Certainly, I’m
sure everybody is tired. Fatigue is probably the most common complaint that people complain
of, but think of the background noise for fatigue in Canada. If you ask someone on the street,
58% say they’re fatigued. And this is the problem in hemochromatosis- that is, the attribution
of symptoms to the disease. And as we find more and more people through screening projects,
we find more and more people who are asymptomatic. So every time I present a graph like this,
these bars are getting smaller. So arthritis would be the most common symptom and arthritis in
the hands, in the MCP joints of the hands are characteristic. Pigmentation of the skin, I’ll show
you a picture, problems with the liver, diabetes, and congestive heart failure. The most common
way that the diagnosis is made now in Canada is that the patient comes in fatigued, the doctor
orders a ferritin thinking it’s going to be low and in fact it’s high.
Here’s a picture of the liver; it is kind of unusual picture. This is a whole specimen on a patient
with cirrhosis and the top bit has been stained with an iron stain. We’d be more familiar in
seeing an iron stain on a microscopic sector but all this blue staining is iron so it’s all
throughout this liver. How common is cirrhosis? The situation is a bit like that mentioned by
the previous speaker in the hepatitis C talk, that if you go to the Liver clinics, cirrhosis from
hemochromatosis is common. If you go out into the community with a screening study it’s very
uncommon. There’s just been a screening study done on 65,000 people in Norway, 3.7% of the
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men were found to have cirrhosis, none of the women.
How do we predict cirrhosis? You might think this is in the realm of the hepatologists, and it is
; but as an insurance person, the number one factor that is going to predict an individual’s risk is
whether or not he or she has cirrhosis. Do we always need to do a biopsy? The answer is no.
This is a study we published several years ago; the yellow dots have cirrhosis, the open circles
don’t have cirrhosis. You can see that if the AST is normal and the ferritin is under 1000,
nobody had cirrhosis. This is the argument for early diagnosis with screening and treatment. It
was much easier to predict who didn’t have cirrhosis than who did have cirrhosis. And if you
really want to know, you probably have to do a biopsy.
Who is biopsied? In my clinic, we’re doing biopsies in C282Y homozygotes with suspected
problems with the liver - abnormal liver enzymes, splenomegaly, ascites. We’re doing biopsies
in people with concomitant risk factors - alcohol or hepatitis C - and I might add this is not as
common as you might think. If you read old textbooks, they’ll tell you that 25% to 30% of
hemochromatosis patients are alcoholics. It’s not true at all and in fact most of those cases are
iron overload secondary to alcohol and now that we do the gene test they don’t have
hemochromatosis at all. We’ve estimated the prevalence of alcohol in our population at about
4%. If you have a carrier, that is the C282Y heterozygote, that is behaving like a homozygote,
that is the ferritin is greater than 1000, I would consider doing a biopsy because these people
may have some other type of gene that we haven’t yet discovered, some other mutation. And
this is probably the most important one. Iron overload in a patient who does not have the typical
genes of hemochromatosis because these are the people that turned out to have alcoholic
hepatitis, hepatitis C, hepatitis X, whatever. And many of these patients do not even have iron
overload when we do the biopsy.
Let’s turn back to the symptoms. These are the hands of a surgeon at my hospital who had to
give up surgical practice because the arthritis in his knuckles were so severe he could not operate
anymore at age 55. I show this because some of my colleagues in the cafeteria sometimes make
me feel like hemochromatosis is some kind of ‘quack’ disease - some sort of chronic fatigue
type condition in which you can’t touch it, you can’t feel it, nobody gets sick from it. It’s not
true. There are some people that get very sick from it. This is the pigmentation of
hemochromatosis. This is the patient on the right, this is his wife and this pigmentation is a very
late finding. It depends on the degree of iron overload and if you’re waiting for somebody with
bronze diabetes to come in your office, you’ll be waiting a long time. It’s a rather subjective
finding and it’s much easier to interpret once you know the serum ferritin.
As I mentioned before, the background noise of symptoms is extremely high in
hemochromatosis. This is why, when an aging patient comes into the office with arthritis and a
touch of diabetes, the family doctor doesn’t jump to doing iron tests. We addressed this in a
paper we published several years ago with the CDC in Atlanta; we did a survey of 2,851
hemochromatosis patients, and compared it to 33,000 so-called normal people - people enrolled
in the NHaines3 study in the U.S. This is self-reported arthritis, it’s not x-ray. And if we look
at women here age 40 to 59, we see that our hemochromatosis women have more arthritis than
the general population but as we go over age 60, the general population has more arthritis than
our hemochromatosis women and then this could not be explained by these people dying off.
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We do have a treatment for this condition, it’s a rather old fashion treatment, it works very well:
periodic bleeding. We tend not to use any animals or leeches for this technique. There are
several instruments that can be used. It depends on whether you like the patient, which health
plan you are in, that sort of thing.
What’s the natural history of hemochromatosis
(see graph)? Here we see data from our center,
where we have a 20-year follow up. The major
factor affecting long term survival is cirrhosis,
and there’s quite a significant difference
between cirrhotics and non-cirrhotics. These
people were all treated from the time that the
diagnosis was made, which in the case of those
with cirrhosis was usually at a late stage. The
same pattern is evident with diabetics and nondiabetics – so that diabetes is also a major factor affecting survival. And that’s not surprising
because most people that have cirrhosis have diabetes, that is, these are the same people as the
people that have cirrhosis.
Let’s look at the gene testing. This is an autosomal recessive condition, so it’s much easier to
predict than breast cancer genes and so on. If you have identified a family, statistically you
would expect to find two carriers and one normal genotype. Keep in mind that anytime you get
into this type of testing, it assumes that the parents are who they think they are. Once we
identify a patient with hemochromatosis, the major people at risk are the brothers and sisters,
with a 1 in 4 risk of having it. This is sometimes hard to get through the patients who are
usually more interested in their children. In fact the risk to children is much lower because it
means that the spouse also has to be a carrier - and the risk of 1 in 20 assumes a Caucasian
marrying a Caucasian; if they marry a black person or Filipino, all bets are off. Because of this,
we in our clinic have used spousal testing quite frequently, because the children are all over the
country or in California, in the States and/or in different health care plans. This use of spousal
testing has simplified our approach to studying families.
Are there any other genetic mutations? There certainly are and this list is growing. But I’d
really emphasize in this talk that the most common one is the C282Y homozygote. I touched on
the compound heterozygote, this is more common than this in the general population - this is
about 1 in 50. This one, H63D homozygote is about 1 in 30. This is a new mutation in the
tranferrin receptor. We looked for this in 800 people and we have not found a carrier yet.
Juvenile hemochromatosis is another disease with iron overload. This is a very frightening
disease for a doctor. The patient presents with fulminant heart failure, usually under the age of
30 and it can be very rapidly fatal; it is probably a mutation on chromosome 1.
Aceruloplasminemia, another new disease described that is on chromosome 3. And there is nonHFE iron overload - there’s a lot of discussion about this, about whether African -Americans
have their own type of iron overload, maybe whether this could be linked to the Bantu siderosis
in Africa. There has been a family reported in Italy that seems to have non-HFE iron overload.
Neonatal hemochromatosis again is a different condition, often fatal.
How are we going to sort all these problems out? This is probably the way we are heading.
This is a gene chip, and this technology is here. This is a microarray type setup, and you can
test for 2,000 genes at once. We can envision that we could put all these iron genes and
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protogenes on to one of these chips and pass it with a simple blood sample on the way through.
This is printed out as your own personal bar code like the airline boarding pass and it’s got the
funeral date on the back. We have to decide whether we want this technology to be used,
because this technology is here.
I see people that come to my clinic who have
hemochromatosis, at least the proband does; and we’ve often suggested that there are a lot of
undiagnosed cases out there. But now that we have gene testing, we are beginning to realize that
there are many so-called non-expressing hemochromatosis patients. They have two copies of
the abnormal gene, they don’t have iron overload, they don’t have any symptoms and they’re
adults.
Well, how can we get a feel for this? This is the kind of study that we need more that would be
good for insurance people. The natural history of untreated disease. And you know now we
have a treatment, so it’s somewhat unethical to say we’re going to randomize half the people to
have bleeding and half the people not to have it. So this is a new approach. This was published
in the New England Journal from Australia. It’s called the Bustletone study. This is a little bit
like the Framingham study, and everybody is Bustletone in the west of Australia has a blood test
done every year. They are studying all aspects of health with this, whether it’s cholesterol,
sugar, blood pressure, and so on; the whole town has bought into this and in exchange they get
enhanced health care. In this study, my colleagues tested 3,000 people for hemochromatosis on
blood samples and found about 1 in 200 had it. And then because of the nature of this project,
we were able to go back and look at blood tests four years earlier on these people with no
treatment in between. In some of the men the ferritin was rising at a pretty good clip but in
some of them it’s not; and many of the women started with a normal ferritin and it did not
increase. About half of the people in this sample did not have an increase in their ferritin. So I
want to leave you with this idea that not everybody that has hemochromatosis is progressing on
to cirrhosis and all sorts of problems. What we are trying to sort out now is what percentage are
like this.
What about the carriers? There’s lots of stuff in the popular press saying that carriers have an
increased risk of heart disease, cancer, and so on. The studies that are negative are about 10 to
1, but it’s the ones that are positive that are always picked up by CNN when they are not finding
an epidemic. And to address this question, we decided at our center that we would look at
people that had transplants of the liver for other reasons – hepatitis C, alcohol, whatever - and
we would do gene testing on their explanted livers. And if they are more susceptible, there
should be a higher prevalence of carriers in this group. And here we see that the problems were
about 10% which is very similar to our general population study of about 5,000 patients. So we
don’t think that carriers are at an increased risk of cirrhosis. I’m not convinced myself about
the heart disease story and in fact you can make an argument that there must be some protective
effect of being a hemochromatosis carrier and during times of the bubonic plague and the potato
famine in Ireland and so on, these people did quite well. In fact, there’s an abstract out from
Norway that says that homozygotes for hemochromatosis have a decreased risk of heart disease
and we certainly are not seeing a lot of heart disease in our homozygotes.
What about iron and alcohol? This has always been a confounding variable. It used to be
probably the most difficult diagnostic problem in my clinic. And this is an area where gene
testing has been tremendously helpful in sorting out this problem.
I just want to close talk you about population screening. This is something I’m involved in a
very big way now. And the concept I think is simple, that you can spend a little bit of money on
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cheap diagnostic test for iron overload to prevent perhaps the complications of
hemochromatosis - cirrhosis, heart failure, diabetes, etc. Whether or not this screening is a
good idea depends on your perspective. For example, you’ve probably heard the story that
smoking saves money for the system because these people die early and you don’t pay for them
in a nursing home. That’s one perspective. Whether this is a good idea for hemochromatosis
depends on a lot of variables; like the prevalence, which we’ve shown is high, how good are the
screening tests, how expensive are these screening tests. Again, hemochromatosis does well on
that. The one we’re really fuzzy on is the natural history of disease. That is, what’s the good of
picking up people that wouldn’t get these problems anyway? We did a screening study in
London, Ontario. We screened 5,211 voluntary blood donors and we found 1 in 327 were
homozygotes. This was a mixed population, it was about 90% Caucasian. If we dropped out
some of the ethnic groups, this number was about 1 in 250; and we found some carriers and
some compound heterozygotes.
That was the prelude to the HEIRS study for which I am one of the principal investigators, and
which is a $40 million dollar project sponsored by the NIH in Bethesda, Maryland. HEIRS
stands for Hereditary Hemochromatosis and Iron Overload Screening study. In this study,
100,000 people are going to undergo testing for iron overload, with gene testing, transferrin
saturation and ferritin. 20,000 of them are going to be tested in London. There is a small part
of our study that takes place in the suburbs of Toronto, Washington DC, Birmingham Alabama,
Irvine California, Honolulu and Portland. The study has been going for one year and there have
been about 10,000 people screened already; the data from the study is not quite ready for prime
time. This will be the study that decides whether the US moves towards screening for
hemochromatosis across the whole country, so this will have a huge impact on the insurance
industry - if everyone in the whole country is going to have a gene test done.
What do we know from these screening studies that have been done already? The biggest one,
which is going to be published in about one month, is from Norway where they screened 65,238
people and they found that 3.7% of the men had cirrhosis, none of the women. The prevalence
of the gene for hemochromatosis was about 1 in 200. These are some of the other studies; that
was our study, San Diego, Australia and Norway. There are studies in progress in 15 countries
in Europe at the present time; so there’s going to be a huge amount of data on this. And the
general trend of these things is - high prevalence but not much disease.
Are we creating disease? This is an important question in the gene testing area. People in the
States are absolutely terrified of the idea that they can have gene testing and be turned down for
health insurance. Up here, we have some concerns also from the insurance industry and I’m
very anxious to hear your opinions on that; because the number one impediment to population
screening here in Canada is this uncertainty about how gene testing will be viewed by the
insurance industry. There are other possible side effects of gene testing and these include
labeling, stigmatization, occupational discrimination, that sort of thing. For example, not far
from here, in the steel factory in Hamilton, David Sackett went and did a screening survey for
hypertension and they found quite a few people that had it, and started them on treatment. A
year later they went back and they found that most of those people who had been diagnosed as
hypertensive had taken all kinds of days off work during the year, after knowing they had it
despite being asymptomatic all the way through.
Because of this concern, in our study we did psychosocial testing before and after gene testing.
We used standard instruments and we did psychological interviews, and we actually sent our
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psychologists out to see people one year later and find out whether they had taken more time off
work or whether they had any problems with insurance. All these things were negative. In fact,
this is their anxiety score - shown here for the homozygotes - and you can see in some of these
people the anxiety went down; these are people that had volunteered for a screening project for
hemochromatosis. Our current consent form for this project sponsored by the NIH being a US
study is about five pages and says all sorts of things about you may be turned down for
insurance and so on. And we have about a 75% compliance rate with the study. This is the
concept that we’re left with: that there may be a whole bunch of people out there that carry two
hemochromatosis genes that have a normal transferrin saturation and ferritin - I’ve estimated
this might be 50%. People who are more skeptical say it may be 10%. There is a group of
people that have a high tranferrin saturation but a normal ferritin; this pattern is common in
children or young women. There’s this group that’s the most common in my clinic: high
transferrin saturation, high ferritin but no symptoms. And then there are people that have organ
damage, the people that you want to know about, the people that have cirrhosis and diabetes.
What we really want to know is what is the rate of progression between these groups? My
own feeling is that this group is probably not progressing – ie if you’re an adult and both these
blood tests are normal, you are probably not going to progress, although some people think that
this could change after the menopause in women. Where is this all going? I don’t think that
we’re going to end up with one big line up, sort of a Stalag setup, for centralized genetic testing.
It is more likely that when more of these studies come out, and some of them are out already,
doctors are going to become more aware of iron overload; and in patients at risk, who are
patients of Celtic or Scandinavian heritage, they’ll consider doing an iron test like transferrin
saturation in the same way that they might order a serum cholesterol.
Just a few comments about insurance to conclude. Non-expressing C282Y homozygotes may
never develop iron overload. Early diagnosis and treatment for poor organ dysfunction leads to
an excellent long term survival, so screening could possibly improve insurance risk. C282Y
homozygotes should have clinical evaluation of organ dysfunction to determine their insurance
risk, and this may include biopsy of the liver, blood sugar studies, etc. And severe iron overload
from any cause is a risk factor independent of any gene test result. Significant iron overload is
rare in compound heterozygotes, simple heterzygotes, and H63D homozygotes. And the
somewhat unique aspects of gene testing for hemochromatosis are that the disease is very
common, very treatable, and not everyone who has the genes gets the disease. Finally, I just like
to conclude these studies were done in three countries with a variety of colleagues particularly
with Dr. Barber who passed away two years ago.
Thank you very much.
Questions
Dr Howard Minuk: I really enjoyed your talk, Paul. It’s absolutely outstanding. Two questions.
One, is the risk of cirrhosis from hemochromatosis any different from the risk of cirrhosis from
alcohol or hepatitis B? Secondly, it’s not so unusual for us to see somebody that’s been picked
up on screening test with an elevated ferritin to have mild to moderate cirrhosis. Are those
people at risk for progressive cirrhosis and/or hepatocellular carcinoma?
Dr Adams: Well to answer the first question, in this condition, when you have cirrhosis, a
treatment is instituted and once the patient is iron depleted which can take a long time in a
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cirrhotic patient, we think we’ve stabilized their condition. So it’s very uncommon to have a
progression of the cirrhosis. And one of the examples of this is at our centre, we’ve done about
1,800 transplants of the liver. We’ve only transplanted two patients with hemochromatosis and
yet we have 395 families in this area. So this differs from hepatitis B where there’s ongoing
injury although there are some new treatments in that area as well, and alcohol in the patient that
continues to drink. They continue to be at risk fof cancer of the liver. There’s some controversy
about screening these patients for cancer with ultrasound and alpha fetoprotein. The
controversy is not whether you can find early tumors, it’s what you do about it when you find
them.
The second question about the patient with a mild ferritin elevation, I think the patient probably
doesn’t have hemochromatosis. You’ve got to remember that ferritin goes up in any type of
inflammation. About 70% of hepatitis C patients have high ferritin. In fact it’s so common in
the general population we are starting to ask ourselves whether we’ve got the right normal
range. Because when you start to test 20,000 people you find that there’s all kinds of people
who have a ferritin between, say, 300 and 700. If you took all comers with that scenario,
probably the most common situation is fatty liver or NASH (Non-alcoholic steatohepatitis),
usually non-cirrhotic and if they’re non-cirrhotic, I don’t think they have a risk of cancer.
Question: First of all, I’m interested in your figure of 75% pick up rate among your volunteers
for screening despite the proviso that they may not be able to get insurance. The second one is
that I think you are in danger of inventing a disease. The problem is that hemochromatosis up
until the recognition of its genetics was defined clinically, and most insurance risk assessment is
based upon that clinical assessment. What’s happening now of course is that you have this
group of people who are under the water, in the bulk of the iceberg, who are being re-labelled as
having a disease; they don’t have a disease, what they have is a genetic predisposition to a
disease, and I think that we in the insurance industry need to take them on board and perhaps
clinicians need to as well.
Dr Adams: I think that’s a very good point. And we’ve struggled with this at the NIH about
case definition, that is - a C282Y homozygote with no iron overload - is this a case or a patient
or a person? In regard to the 75% uptake, the study is also going off on one of those places in
the US and on the US consent form, it says specifically that they may be turned down for health
insurance. Our form just says insurance and that the compliance rate so far in the US is lower,
ranging from 30% to 50%. Some of you might have seen 60 Minutes last night where they were
talking about the E code project in Iceland where they sold all of the DNA to this private
company; and some of these issues came up.
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APPENDIX - (Meeting handout)
Update on Hemochromatosis
Paul C. Adams, M.D.
Professor of Medicine,
London Health Sciences Center - University Campus,
P.O. Box 5339,
London, Ontario
Canada N6A 5A5
Ph 519-663-3513, FAX 519-663-2997, email [email protected]
Genetics
The big news in hemochromatosis is the discovery of the gene for hemochromatosis (HFE) and the development of a
genetic test which can readily be done on a blood sample or stored tissue.
The C282Y mutation on chromosome 6 of the HFE gene is present in 93 - 100 % of homozygotes in pedigree
studies. In less well defined patients with iron overload the prevalence ranges from 60 - 80 %. A second mutation,
H63D is less common and its relationship to hemochromatosis is less well defined.
Use of the C282Y genetic test for hemochromatosis
The genetic test is most useful in a patient that is suspected of having hemochromatosis clinically or with an elevated
transferrin saturation and / or serum ferritin. It is also useful when investigating siblings and other family members of
a C282Y homozygote. It will replace HLA typing in pedigree studies.
There have already been a number of cases within hemochromatosis families reported that are homozygous for the
C282Y mutation without iron overload. This may represent incomplete penetrance and the frequency of this
phenomena in the general population has not been clearly established. However, preliminary population studies in
Ireland (1 in 100) and in Australia (1 in 189) suggest that the gene is more common than the clinical disease. This
may reflect a high degree of incomplete penetrance of underdiagnosis of the disease. In London, Ontario, the
prevalence of C282Y homozygotes was 1 in 327 (n = 5,211).
Availability of the Genetic Test
The test is available in Ontario through the provincial DNA diagnostic laboratories. The test is done without charge on
a 5 ml lavender top tube (EDTA) that can be sent without refrigeration. The typical hemochromatosis patient is a
C282Y homozygote. Other Canadian labs doing the test can be found on the website http://home.iSTAR.ca/~chcts/
Other diagnostic tests for hemochromatosis
Transferrin saturation - is better than serum iron alone, available, inexpensive, fasting is better than random. This test
is elevated even in children with hemochromatosis. Thresholds for investigation vary from > 45 to 62 %.
Unsaturated iron binding capacity – this is an old test that can be done for < $1 and has shown promise as a screening
test.
Serum ferritin - is a good indirect measurement of body iron stores. Increases with age in hemochromatosis. Can be
elevated in all liver diseases and chronic inflammation.
Liver biopsy - Since the development of genetic testing, liver biopsy has gone from a diagnostic test to a prognostic
test. A biopsy should be considered in the hemochromatosis patient with liver dysfunction and in the patient with iron
overload that does not have the typical genetic pattern. Hepatic iron concentration is useful and can be expressed as
the hepatic iron concentration / age (hepatic iron index). This is particularly useful in the alcoholic patient. All types
of end stage liver disease can have mild to moderate iron overload.
MRI - The sensitivity of the technique continues to improve. It does not replace liver histology and liver iron
concentration. It can be helpful in a patient with a contraindication to liver biopsy.
Treatment of hemochromatosis
Patients are initially treated by the weekly removal of 500 ml of blood. Patients attend an ambulatory care facility and
the venesection is performed by a nurse using a kit containing a 16 gauge straight needle and collection bag (Blood
Pack MR6102, Baxter, Deerfield, IL) Blood is removed with the patient in the reclining position over 15 - 30
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minutes. A hemoglobin is done at the time of each venesection. If the hemoglobin decreases to less than 100 g/l the
venesection schedule is modified to 500 ml every other week. Serum ferritin is measured periodically (q 3 months in
severe iron overload, monthly in mild iron overload) and weekly venesections are continued until the serum ferritin is
approximately 50 mg/L. Transferrin saturation often remains elevated despite therapy. Patients may then begin
maintenance venesections 3 -4 times per year. Iron re-accumulation is an inconsistent observation and many patients
will go for years without treatment without a rise in serum ferritin. Chelation therapy is not used for the treatment of
hemochromatosis.
Interpretation of genetic testing for hemochromatosis
C282Y homozygote – This is the classical genetic pattern which is seen in > 90 % of typical cases. Expression of
disease ranges from no evidence of iron overload to massive iron overload with organ dysfunction. Siblings have a 1
in 4 chance of being affected and should have genetic testing. For children to be affected the other parent must be at
least a heterozygote. If iron studies are normal, false positive genetic testing or a non-expressing homozygote should
be considered.
C282Y / H63D – Compound heterozygote – This patient carries one copy of the major mutation and one copy of the
minor mutation. Most patients with this genetic pattern have normal iron studies. A small percentage of compound
heterozygotes have been found to have mild to moderate iron overload. Severe iron overload is usually seen in the
setting of another concomitant risk factor (alcoholism, viral hepatitis)
C282Y heterozygote – This patient carries one copy of the major mutation. This pattern is seen in about 10 % of the
Caucasian population and is usually associated with normal iron studies. In rare cases the iron studies are high in the
range expected in a homozygote rather than a heterozygote. These cases may carry an unknown hemochromatosis
mutation and liver biopsy is helpful to determine the need for venesection therapy.
H63D homozyote – This patient carries two copies of the minor mutation. Most patients with this genetic pattern
have normal iron studies. A small percentage of these cases have been found to have mild to moderate iron overload.
Severe iron overload is usually seen in the setting of another concomitant risk factor (alcoholism, viral hepatitis).
H63D heterozygote – This patient carries one copy of the minor mutation. This pattern is seen in about 20 % of the
Caucasian population and is usually associated with normal iron studies. This pattern is so common in the general
population that the presence of iron overload may be related to another risk factor. Liver biopsy may be required to
determine the cause of the iron overload and the need for treatment in these cases.
No HFE mutations – There will likely be other hemochromatosis mutations discovered in the future. If iron overload
is present without any HFE mutations, a careful history for other risk factors must be reviewed and liver biopsy may
be useful to determine the cause of the iron overload and the need for treatment. Most of these cases are isolated,
non-familial cases.
Prediction of risk in hemochromatosis
The major factors determining long term survival in hemochromatosis are the presence of cirrhosis and diabetes.
Most diabetics with hemochromatosis have cirrhosis since insulin resistance secondary to liver disease is the cause
of the diabetes. It can be difficult to predict which patients have cirrhosis in the absence of a liver biopsy. It has been
determined in a study of 362 C282Y homozygotes that if the AST is normal, the ferritin < 1000 ug/L and there is
no hepatomegaly, it is very unlikely to have cirrhosis. The role of liver biopsy in the era of genetic testing has shifted
from a diagnostic test to a prognostic test. The long term survival in treated C282Y homozygotes with and without
cirrhosis is shown in Figure 1. These results are better than most other types of cirrhosis since the disease in nonprogressive once iron depleted. These patients continue to be at risk for hepatocellular carcinoma. Cirrhotic patients
have a 200 fold increased risk of hepatocellular carcinoma similar to patients with chronic viral hepatitis B and C.
However, the mean age of carcinoma at our center is 68 years which is older than in cases with hepatitis.
Determination of risk solely based on a genetic test is to be discouraged. It has been estimated that as many as 50 %
of C282Y homozygotes will not express the disease. Furthermore, a young C282Y homozygote discovered before
the development of cirrhosis that undergoes treatment has a long term survival similar to an age and sex matched
population. Compound heterozygotes, simple C282Y heterozygotes, H63D homozygotes and heterozygotes have a
very low risk of iron overload (< 2 %) and organ dysfunction in these cases is rare. Large population screening
studies are in progress in Canada and United States. The HEIRS study will test 100,000 people for transferrin
saturation, ferritin and genetic testing. A major concern about widespread genetic testing is discrimination by the
insurance industry. This study may lead to a recommendation for national screening. An awareness of the natural
history of the disease and the benefits of early diagnosis and treatment should minimize the risk for genetic
discrimination. In fact and argument can be made that awareness of the predisposition to iron overload by genetic
testing, will prevent the disease and improve the life insurance risk.
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Reference List
(1) Niederau C, Fischer R, Purschel A, Stremmel W, Haussinger D, Strohmeyer G. Long-term survival in patients
with hereditary hemochromatosis. Gastroenterology 1996; 110:1107-1119.
(2) Adams PC, Speechley M, Kertesz AE. Long-term survival analysis in hereditary hemochromatosis. Ga
stroenterology 1991; 101:368-372.
(3) Barash C. Genetic discrimination and screening for hemochromatosis: then and now. Genetic Testing 2000;
4:213-218.
(4) Beutler E, Felitti V, Gelbart T, Ho N. The effect of HFE genotypes on measurement of iron overload in
patients attending a health appraisal clinic. Ann Int Med 2000; 133:329-337.
(5) Asberg A, Hveem K, Thorstensen K, Ellekjaer E, Kannelonning K, Fjosne U et al. Screening for
hemochromatosis - high prevalence and low morbidity in an unselected population of 65,238 persons.
Scand J Gastroenterol 2001;(in press).
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