Leukaemia breakthrough: 'It's good if we can help other families'

Sarah Murphy and her husband, Justin, a site manager in Bromley, Kent, have been through the pain of seeing one of their twin daughters diagnosed and treated for leukaemia. They are just one of about 500 couples whose children are diagnosed with the disease each year.

However, the unusual situation they found themselves in – with one daughter affected and the other apparently healthy – turned out to have a hidden benefit. Scientists were able to compare the DNA of the twins to see if they could tease out the possible reason why one twin, Olivia, contracted the disease while the other, Isabella, was unaffected.

"What we have always said is that anything that would improve the treatment we would be very, very happy to contribute to," said Mrs Murphy, 35. "We don't mind doing anything if it helps the research. Without the research we wouldn't have had the treatment available to us. If we can give something back we will."

Olivia is in remission but has become blind in one eye due to an infection brought on by the chemotherapy drugs that have to be used to eliminate the leukaemia cells from her body. "We have seen the families who have gone through all the chemotherapy," said Mrs Murphy. "Anything which leads to a lessening of the intensity of the chemotherapy which can help other families is a good thing.

"We have always said if it was going to happen, it happened to the right one, if you can say that. Olivia is a real toughie. She just gets on with it whether it is taking drugs or having treatment. Isabella is a real drama queen. You always know when she is ill. If it was to happen to Isabella, she would be more awkward.

"I don't think the other children at school are too aware of the treatment, although Olivia's eye is quite noticeable now.

"Olivia has been left shorter because of the treatment and her hair has grown back curly. Parents say to us: 'I thought you had identical twins', and I say 'We do'. But Olivia will grow."