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Mr and Mrs Peterson

Mr and Mrs Peterson attend the genetics clinic to discuss Mrs Peterson's family history of cancer.
Hello, Mr. and Mrs. Peterson. Nice to meet you. My name’s Dr. Roddy. I’m one of the consultants here. How are you both? Good. Yes, fine, thanks. Yeah. OK. We’ve been asked to see you by your GP to talk about your family history of cancer, Mrs. Peterson. Yes. After reading things in the paper about Angelina Jolie, I just realised that I’ve got a similar family history. And it just made me think maybe I have a similar kind of story. OK. And apart from talking about your family history of cancer, do you have any other questions that you want to have answered today? Not really. OK.
So in order for me to find out about your family history, I need to know a little bit more about you. How old are you now? 38. And are you well in yourself? Yes. And do you work? Yes, I do. What do you do? I’m a project manager. OK. And you, sir? Are you well in yourself? Yeah, yeah. Yeah, yeah. And how old are you? I’m 38. And do you work? Yeah. What do you do? I’m an actor. OK. Mrs. Peterson, have you got any brothers or sisters? I do, yes. Who have you got? Two brothers. And have they both got the same mother and father as you? Yes.
I’m just going to sketch out your family tree while we talk. What are your brothers called? David and Stephen. And your parents, are they both with us? No, they’re not. They’ve both passed away? No, my dad is still alive. And your mother’s passed away? Yes. What was her name? Jenny. And what did she die of? Breast cancer. How old was she when she died? Do you know? 36. And did Jenny have any brothers or sisters? She did. She had a sister. What was her name? Jean. Is she still alive? She’s died recently. What did she have? Ovarian cancer. Do you know how old she was when she died? 56. And did Jean have any children? She did, yes.
What children did she have? Two sons. Do you know their names? Yeah. Daniel and John. What about Jenny’s parents? They still with us? No. Have they both passed away? Yes. Do you know what they died of? Well, my grandmother died. I didn’t ever know her. She died of breast cancer, too. And what was her name? Doris. And grandpa? His name was Richard. Did he have cancer? No. OK. I know it’s very difficult thinking about the people in our family who’ve had cancer. Apart from your mum and her sister Jean and her mother Doris, have other people in the family had cancer? Not as far as I know. OK.
And you’ve come here today because you’re concerned about your family history of cancer. What have you read about in the newspapers? You made a reference to Angelina Jolie. Well, like I said, it’s a kind of similar story, that I think her mother died of breast cancer or ovarian cancer, and her aunt died of breast cancer. So it’s like the same combination. And it just got me thinking, really, that the fact that my mum died so young and my aunt is only 56, and my grandmother died so young, it just made me think maybe I have a similar mutation, genetic mutation. OK. So you’ve read about genetics with regard to cancer? Yes. OK.
Before we talk about genetics specifically, let’s just have a general discussion about cancer and what causes it, because it’s important to know that cancer’s a very common condition in the UK and affects, we think, about 1 in 2 of the population over the course of their lifetime. Breast cancer, in particular, is very common in women, as I’m sure you know, and we think affects about 1 in 9 of the female Caucasian population in the UK. So cancer is common, and breast cancer is common in women.
But when we see lots of people in a family and affected at a young age, and particularly when there’s breast cancer happening in conjunction with ovarian cancer in the same family, we do have to be suspicious that the cancer could be caused by an inherited gene mistake. I don’t know how much either of you know about science, but I’m going to assume you know nothing, and we’re going to have a discussion now about how genes are passed on in families and what genes are. And the first thing I want you to know is that our bodies are made up of millions of cells. And inside every cell, there’s a dark area called the nucleus.
And if we look at that nucleus, what we see are these, and we call these chromosomes. I ask patients to imagine that this pile of chromosomes is like a pile of socks, because if it was socks, you’d pick up one and have a look around to find the other one to make the pair. And having put the chromosomes into pairs, what we see is this. What we see is that some of the chromosomes are much bigger than others, and so we put them into size order and give them a number. It’s nothing more scientific than that.
And the final thing I’ll say about chromosomes is that all of us, men and women, have got exactly the same chromosomes from 1 to 22. And the last pair of chromosomes, in women like us, is XX. And in men, like you, Mr. Petersen, is XY. I don’t have a picture of that today. Now, the reason that we’ve got two copies of all of our chromosomes is because we get one from our mothers and one from our fathers. And when we have children, we pass on just one copy of everything to each of our children. And what gets passed on is completely random. Let’s just have a closer think about the chromosome.
And I want you to imagine that a chromosome is like a string of beads, where the chromosome is the string and each bead is what we call a gene. And all a gene is is an instruction that tells our bodies how to work. So some genes determine the colour of our hair, the colour of our eyes, the colour of our skin. And some genes are very important for the way our internal organs grow and develop. Now all of us have got two copies of genes called the BRCA1 and the BRCA2 genes. And I know that these are genes you’ve read about. Yeah. And these genes are very important for the normal functioning of our breast and ovarian tissue.
And mistakes or alterations in these genes will increase the likelihood of somebody developing breast or ovarian cancer. Mr. Peterson, you look quite worried. Have you got anything to ask? Well, no. I mean, you’re just– I suppose my worry has always been what this means for our children. We’ve got two children. And so I’ve just been thinking about whatever we might find out and what the implications are for our kids. OK. So I haven’t yet asked you about your children. You’ve got two. Who are they? Ella and Henry. And how old are they? Seven and four. Ella’s seven? Yes. OK. I can completely understand that you’re worried about your children.
At the moment, while they’re so young, their risk of developing any type of cancer is very low. So I think that today, we need to focus on Mrs. Peterson and her family history of cancer. So Mrs. Peterson, I’ve told you already that whenever we see lots of people in a family affected by cancers, particularly when we see breast and ovarian cancers in the same family, and when people are affected at a young age, we do worry that those cancers could be caused by mistakes in genes.
And if we speculate that your mother had a mistake in the BRCA1 or the BRCA2 gene that caused her to have an early onset cancer and that she inherited that gene mistake from her mother, then there is a 50/50 risk that that gene mistake has been passed on to you. And I’ll just go over that again. I’ve said that we’ve got two copies of all of our chromosomes, and that means two copies of all of our genes. We’ve all got two copies of the BRCA genes. And if one of those genes has a mistake in it, it will greatly increase the risk of developing cancer.
And if somebody’s got a gene mistake, there’s a 50/50 chance of it being passed on.
The position that we’re in for you, Mrs. Peterson is because of your family history, we could take a blood sample from you, if it’s what you wanted, to test it for mistakes in the BRCA1 and the BRCA2 genes. If we found that you did have a gene mistake, then that would mean that you’re at a greatly increased risk of developing breast and ovarian cancer. Yeah. If we found that you did have a gene mistake in the BRCA1 or BRCA2 genes, then that would mean that each of your children had a 50/50 risk of inheriting that mistake from you.

Mr and Mrs Peterson attend the genetics clinic to discuss Mrs Peterson’s family history of cancer.

Please note: Mr and Mrs Peterson are fictional characters invented for teaching purposes, and these clinical scenarios are designed to exemplify teaching points, rather than represent what would occur in the genetics clinic. Any resemblance to any real individuals is purely coincidental.

Talking point

What factors would impact on your decision when considering genetic testing?

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The Genomics Era: the Future of Genetics in Medicine

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