BRITISH BROADCASTING CORPORATION
RADIO SCIENCE UNIT
CHECK UP 4. - Inherited Diseases
RADIO 4
THURSDAY 16/12/04 1500-1530
PRESENTER:
BARBARA MYERS
CONTRIBUTORS:
FRED KAVALIER
PRODUCER:
ANNA BUCKLEY
NOT CHECKED AS BROADCAST
MYERS
Well if there was a chance that you might develop a life-limiting inherited disease would you want to know? Would you be like Steve in the play just now or like Victor preferring to stay in the dark, trading hope against certainty? It is a stark choice in Huntington's Disease, anyone whose mother or father has the disease will have a 50/50 chance of developing the condition in middle age.
Now patterns of inheritance in other genetic diseases are not quite so clear cut. With sickle cell anaemia, cystic fibrosis and muscular dystrophy, for example, the disease strikes early in those children who inherit the faulty genes, though the parents are carriers of, rather than themselves victims of the disease.
Whatever the particular condition the question is about genetic screening - testing - what diseases can be tested for, what should be screened for and what are the consequences of discovering the degree of risk that runs in your family?
Well to answer your specific questions today I'm joined by Dr Fred Kavalier, who's a doctor in the genetics department of Guy's Hospital in London. And please phone us - 08700 100 444 - with your question or you can e-mail checkup@bbc.co.uk.
Michael has phoned us, he's on the line. Michael your question please.
MICHAEL
I don't actually have a question but basically just a statement in terms of my father was diagnosed at 42, that was about six, seven years ago, with Huntington's and basically obviously it's a big question of whether or not to actually get tested. But in the end - and obviously watching his deterioration - I basically decided that I couldn't cope with knowing that I definitely had it. So it was really just to support the programme and because I think awareness for everybody is a good thing. But the only other element to this is on the finance side of starting families and getting married and so on - it does have quite big implications in terms of people who have relatives that have Huntington's but haven't been tested, can't get life insurance, well if they can get it it's actually very, very expensive and there's lots of issues like that which are like day to day issues.
MYERS
Michael thank you for coming on to tell us that and I'm sorry to hear about your father and it is very interesting indeed that you have chosen to live with the uncertainty in your own case. And I'm just going to ask Fred Kavalier to comment on that. A perfectly reasonable choice, if that is your choice?
KAVALIER
Well I think the first thing to say is that of course it is your choice Michael and it's not anybody else's choice about whether or not you should have the test and no one is in the business of encouraging or discouraging people to have tests - it really is a personal decision. With regard to finance and insurance - I mean people are often very worried about this and it is a real issue, you see, because whether or not anyone has a genetic test simply knowing that somebody in the family has got a condition lets insurance companies know that there is a risk.
MYERS
You have to declare that on your forms for example.
KAVALIER
Yes yeah, insurance companies will ask are your mum and dad still alive and do they have any illnesses? So if you say my dad's got Huntington's Disease they know enough to know that this means there is a risk that you could get it.
MYERS
So that could work against you because they will make the assumption that you have a 50/50 chance and therefore perhaps the terms of your insurance will be rather prohibitive.
KAVALIER
Yes, as Michael said either they'll refuse to insure you for life or a mortgage insurance or they will say to you we're going to charge you a lot of money because we think the risk is high. So what people often think - oh well having a test is not going to help me with regard to insurance but the other side of the coin of course is if someone were to have a test and discover that they don't carry the gene for Huntington's - i.e. they're never going to develop it themselves - it's possible to wave that test result in front of the insurance company and say my dad's got it but look I'm not going to get it. So that could help. But I don't think that's an adequate reason to have the test if you have other reasons for not wanting to have one.
MYERS
Michael thank you very much for that. If I can add in an e-mail from Jill. Now she took the opposite view, she took the test 11 years ago and fortunately it proved negative - her father had died of Huntington's - and she'd always known that when a test was available she would take it. And in fact she goes on to say that she had her two children after she'd been tested and wouldn't have had children if there had been no test available. Fred, of course that does raise this question - I don't know if it's relevant to Michael - but if you have a test and whatever the result of course it will have implications in this case for your children if you choose to have children. Again is this the right time to think about it even more seriously when you're considering whether you might be passing this risk on to children?
KAVALIER
I think that is the time when people often do think about this most because it's one thing getting an illness yourself but there's something rather sort of terrible people feel about passing something on to their children, we all want to do our best for our children and we have no choice over what genes we do pass to our children, it just happens through biology, so that is the time when people often think about having tests, when they're thinking about having children.
MYERS
But you've said already you can't tell people to do, they must make their own choice. I mean how do you help though in genetic counselling to make the right choice - is it a matter of almost listing the pros and cons?
KAVALIER
I think we do put things in the balance, as it were, saying this is - these are the arguments in favour, these are the arguments against. People have their own family experiences, so that they know what diseases - what effects a disease has had within their family and often with a disease like Huntington's Disease unfortunately it's quite terrifying because it's not a good disease to get. So we give people information, we give people a lot of time to think and talk about it and we never, never rush in to things and always give people the opportunity to change their minds and say actually I don't want to go ahead with this.
MYERS
Not surprisingly we've come off the back of the play and we're talking about Huntington's and that's very relevant, but we shouldn't get it out of proportion, this a rare disease.
KAVALIER
Huntington's Disease is a very rare disease and probably most people who are listening to this programme will have never met or seen a person with Huntington's Disease. Fewer than one in 10,000 people will have this disease. The average GP won't have any patients at all with Huntington's Disease in his practice.
MYERS
Now cystic fibrosis is a more common disease and we have a caller - Christine - who wants to talk about it. Christine your comment or question please.
CHRISTINE
Right the comments I'd like to make. I discovered about seven or eight years ago that my brother was a carrier of the F508 gene for cystic fibrosis.
MYERS
Did he have a test?
CHRISTINE
He did as a result of infertility treatment in Australia. So when I found this out I was concerned, not for myself, because obviously being in my late 30s I knew wasn't going to develop the disease but I have three children. I consulted my GP who then referred me on for genetic counselling. I went through all the pros and cons as the professor discussed with the counsellor and decided that I wanted to undergo the test, which proved positive. The next stage was then to find out which side of the family was the carrier and as my father had died and my mother proved negative we knew which side of the family that the gene was carried through. Now I felt that I needed to know for the sake of my children if I carried that gene I wanted to be able to give them the information when they were old enough to understand and to act on that information that would enable them to make choices for themselves as to whether they underwent genetic counselling and then determined that they were in fact carriers and whether they then wanted to think more carefully about having children.
MYERS
Have you not told them then?
CHRISTINE
I've certainly told my son - he's 15 - and he knows that there's a possibility that he may carry this gene. He's not concerned about it at the moment, I don't think he really needs to be until perhaps he's 18 or older when he can make the decision for himself to seek advice from the GP as to whether he should undergo genetic counselling.
MYERS
So Fred on this then because Christine is a carrier, clearly she hasn't got the disease, her three children haven't got the disease, but could this carrier status go through them and then forward into the next generation and what are the chances of that happening?
KAVALIER
Well the way genes work is we get them from our parents and we pass them on to our children. So things do pass from generation to generation. But I think it's very important to make the point that cystic fibrosis is one of these conditions where you can carry the gene for it and not be affected ever in your life. The only way that you're ever affected by the disease called cystic fibrosis is if you inherit one of these gene mistakes from both of your parents. So if Christine's partner isn't a carrier of cystic fibrosis there wouldn't have been any risk at all that any of her children could ever get that disease. And similarly if any children prove to be carriers unless they marry someone who is also a carrier of cystic fibrosis none of their children will ever have the disease called cystic fibrosis. So it can lie within us for many, many generations and indeed if you look at all the genetic conditions that you can be carriers of we believe that everyone is a carrier of three or four rare genetic conditions. But the lucky thing is we don't usually marry someone who also carries that same thing.
MYERS
Well it's lucky but is it also a matter of good management. I mean Christine I don't know what you would think, somewhere along the line when your son decides to get married, perhaps finding out his status might encourage him to go forward and ask his future partner to find out her status and it may or may not be the making or the breaking of a relationship. Would that be reasonable Fred to actually almost choose your partner depending on their status is you are one half of what could be potentially a dangerous pair of genes?
KAVALIER
Well this certainly happens in some parts of the world because in some parts of the world where a disease called thalassaemia exists quite widely partners get together, families get together, to see whether potential partners are carriers and it's one of the considerations before marriages are made in these parts of the world.
MYERS
So much for romantic love. What do you think about that Christine, I don't suppose you have quite discussed it in that much detail with your son?
CHRISTINE
No we haven't discussed it in any great detail but my belief is that power - or knowledge is power and therefore if you are aware that you could be passing this gene on to your children and you have the test you can then make a really informed decision as to whether you want to go ahead and have children, like your lady earlier - Jill - who said that had she proved positive with Huntington's Disease she wouldn't have had children. So it may be that you make a decision that you can't cope with a child who suffers from quite a severe disease or what can be quite a severe disease and therefore you've made an informed decision as to whether or not you actually have children of your own.
KAVALIER
Yes and the other way that some families approach this of course is they're not deterred from getting married to someone else who might be a carrier but they do want to have tests during pregnancy to find out is the baby going to be affected. And sometimes that leads them down the road to say this baby's going to be affected with a very bad disease, possibly which will interfere with the baby's enjoyment of life or will only have a short life, and they decide not to go ahead and have that baby, they have a termination of that pregnancy. On the other hand sometimes it prepares them for having a baby who's going to have some problems.
MYERS
So the very same genetic test that will determine if you're a carrier of cystic fibrosis or one of these inherited conditions is the test you can apply to the baby in utero - an antenatal test to see if the baby has the disease.
KAVALIER
Yes, if we know that both parents carry say cystic fibrosis it's possible to see has the baby inherited a dose of the gene from both parents. So if a baby has a double dose that's what equals the disease itself. And that's the test that can be done on babies in the womb.
MYERS
It wouldn't be done routinely though, it's not screening is it?
KAVALIER
No it's not done routinely on babies, most certainly not on babies in the womb because the chance of finding it is very, very, very small.
MYERS
Thank you very much for that call Christine. I'll move on, if I may, to another caller now from Yorkshire - Lesley Wilson - hello.
WILSON
Hello.
MYERS
Hello and your question or point please.
WILSON
Yes, I didn't know about muscular dystrophy until my son was about six, he's now 16 and I found out a couple of years ago that I actually was a carrier of muscular dystrophy. And I have a daughter and she is a carrier of muscular dystrophy as well. Now she's had a little girl and the little girl is fine and she's just about, any day now, to deliver another child. She's opted not to have the test because the risks were far higher to abort a healthy baby. And I was just wondering whether is it all the females that are born carriers or just one out of three say?
MYERS
Oh let's have a little primer then on muscular dystrophy and how it's inherited, what the pattern is.
KAVALIER
Well I think the type of muscular dystrophy we're talking about now is duchene muscular dystrophy is that right?
WILSON
Well it's becker's that he has, but it's quite severe, it's sort of borderline I've been told.
KAVALIER
Well this is one of those muscular dystrophies that are carried by women, so women like yourself and your daughter both carry the gene for this, but you won't be affected in any way yourself because you have another copy of the gene that protects you, you've got a good normal copy of the gene that protects you. But when a boy inherits this faulty gene, because he doesn't have another copy of the gene, then he gets the condition called muscular dystrophy - as your son has, yes that's right, as your son has. Now your daughter has a 50/50 chance of passing on the gene to any of her children. If she has a girl that means a 50/50 chance that the girl will be a carrier, but girls don't get this disease, they only carry the genes. If she has a boy there's a 50/50 chance that the boy will have the disease. So if she's got a boy in her pregnancy there is a chance, quite a high chance - 50/50 - that the boy will have muscular dystrophy.
MYERS
But she didn't want the test lest the test itself had perhaps caused a miscarriage, is that what she ...
KAVALIER
Yeah well I'm sure she was worried that she might cause a miscarriage or - and that a perfectly normal baby might end up not being born and it's a difficult decision for everyone.
MYERS
And she hasn't gone so far as to have the sex of the unborn baby tested?
WILSON
No she hasn't, she's decided not to do that.
MYERS
Brave.
WILSON
Just leave it as it is. My son who has it is 16 is quite a joy to the family and thinking of the possibility of aborting the child is quite daunting really - he's a lovely lad.
MYERS
And that is part of the bigger picture isn't it of course.
WILSON
Yes that's the bigger picture.
KAVALIER
I think it's really wonderful that you've said that because it would be quite wrong for people to go away from this programme thinking genetic diseases are unmitigated disasters. Plenty of us are walking the streets with genetic problems of one kind and another, more or less severe, and we're all members of society and we've all got something to contribute. So genetic diseases - we mustn't let them become a great stigma against people.
MYERS
Thank you for saying that Fred and thank you for giving us the opportunity to say that Lesley and best wishes for your daughter.
An e-mail: My brother has MS - multiple sclerosis - says Bruce Robinson, is there a genetic test available to determine if I could get it?
KAVALIER
Well multiple sclerosis essentially is not a genetically caused disease, so although I'm sure there are a few families around the country where more than one person has multiple sclerosis it's not a disease that runs in families. So the risk of our caller getting muscular - multiple sclerosis I beg your pardon - the risks are very small for family members when one other member of the family has multiple sclerosis - it's not a genetic condition.
MYERS
Diana Russell has a question about what may or may not be a genetic condition. Diana, your question please.
RUSSELL
Oh hello. My mother-in-law died from cancer of the stomach and the liver and my husband died, which is her son, died of cancer of the pancreas. Now is this passed on by genes, as I have children and grandchildren and is there a test for them or should they be tested? I'm sort of quite ...
MYERS
Worried.
RUSSELL
... worried, yes.
MYERS
Yes Diana thank you for that. I mean it would certainly be very unlucky to have so much cancer in the immediate family but does that mean that it's something that may be inherited? Fred.
KAVALIER
I think there's a lot of interest these days in cancer and genetics and you can barely read a newspaper without reading about inherited breast cancer and inherited cancer of the bowel and that sort of thing. The first thing that's important to realise is that the great, great majority of cancers are not due to genes, they're not due to the simple inherited gene that's running in the family.
RUSSELL
Oh good.
KAVALIER
There are some clues to look for when you're worrying about this in a family. And I'd say the biggest clues - are the cancers occurring at particularly young ages? Because we know that when a cancer does have a genetic cause behind it, it often hits someone quite young, so I don't know if your husband and your mother-in-law were affected at young ages but if they weren't I think that would be a good sign.
RUSSELL
My husband was 59 years old and his mother was just in her early 60s when she died.
KAVALIER
Well I wouldn't say that's particularly young but no doubt - I mean it's younger than we would like it to happen obviously. The other thing to say is cancer of the stomach and pancreas as not really cancers that we usually associate with genes. So lots of people with breast cancer on one side of the family, for example, at young ages might make us worry about a genetic cause, for lots of people with bowel cancer at young ages. But I think the signs, from what you've told me, are good in your family and I wouldn't really worry much about your children.
RUSSELL
Thank you very much.
MYERS
Well I hope that's been reassuring, thank you for your call. And to Daniel who's also, I think, somewhat concerned about cancer - the story being what Daniel?
DANIEL
Oh hello there, thanks for taking my call. My question is about prostate cancer - my father and his father both died of prostate cancer and I've got two questions. Could I have a genetic predisposition towards this disease and secondly is there a genetic test I could have done to check this possibility out?
MYERS
And following Fred's earlier question - at what sort of ages did your father and grandfather die?
DANIEL
My father was 72 and I think my grandfather was also in his seventies.
KAVALIER
Okay can I answer your second question first? Is there a genetic test to find out if you have a genetic predisposition to prostate cancer? The simple answer to that is no, we don't yet know of a genetic test that will find that in people. The answer to your second question - could there be a genetic tendency in your family? I think it's possible that there could be a genetic tendency but I think it's much more likely that there isn't a genetic tendency and that it's just bad luck that your dad and your granddad both had the same type of cancer. And the reason I say that is that first of all we don't really think prostate cancer is inherited in this kind of simple single gene sort of way. And the second reason for my saying that is that both of them were in their seventies and that is the kind of age when like it or not men get prostate cancer.
DANIEL
Yeah I realise it's a cancer of older people, although it can kick off about 50.
KAVALIER
Yes and when it does occur younger that is one of the things that makes us concerned that perhaps there is something genetic going on.
DANIEL
It would be interesting to know because - earlier - because by making dietary changes you can perhaps make the odds a bit better for yourself, that's why it would be interesting to know.
MYERS
Might that be true for a lot of things that by attending to diet and all the other things we know about - exercise and the rest of it - we are doing the best for our health, whether or not we in fact have an inherited tendency to any particular life threatening illness?
KAVALIER
Well it's true we can't change our genes can we but we can change the way we live and a couple of simple messages with regard to reducing one's risk of cancer - you may think it's boring - but eating lots of fresh fruit and vegetables and doing exercise has scientifically been proven to reduce cancer risks.
MYERS
Thank you - thank you very much for that call, it doesn't sound as though there's anything particular to worry about Daniel but appreciate your question. And our next questioner is Elisabeth and she's in London. Elisabeth your question please.
ELISABETH
Hello I have neurofibromatosis but neither of my parents did, so I guess I'm a first time spontaneous mutation of the gene and I gather that's quite common with NS. I just wondered if you could say something about how often genetic diseases just do strike out of the blue. And if I could just put a supplementary - you mentioned that MS doesn't tend to run in families, my father had early onset Parkinson's and family medical books tend to say rather darkly that Parkinson's does tend to run in families, so could you explain to me what is the difference between something like that and of a full-blown genetic disease like MS?
MYERS
Some interesting questions, let's see if we can get some interesting answers.
KAVALIER
Well I think we're trying to make the difference here between diseases that are caused by a single gene that goes wrong - one of our 25,000 different genes goes wrong - and diseases that have a genetic influence, probably from lots and lots of different genes that are running in our family. So neurofibromatosis, the disease that you mentioned first, which you have is caused by a single gene - something is - what you called a mutation has taken place or a little mistake has crept into your copy of that gene, which wasn't present in your mum's copy of the gene or your dad's copy of the gene. And that does happen in quite a few cases of neurofibromatosis, quite a high percentage of cases. Parkinson's Disease, for the great majority of people, is not a single gene disease, it's something which there may be a tendency because of lots of genes in the family.
MYERS
Elisabeth thank you for that, I'm afraid that will have to be our last question and answer. As always I'm very grateful to all our callers, those we answered today and those of you who called but didn't get on air. There'll be more information though on our website, that's at bbc.co.uk and you can listen again to this programme or indeed to any other in the series. You can call our free and confidential help line, that's 0800 044 044. And thanks very much to our guest today Dr Fred Kavalier. We will not be here next week at the usual time but we will be back the following week - that's the week after Christmas when we'll be answering your questions about everyday illness and how to get the best from your doctor. Till then have a happy and a very healthy Christmas.
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