The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday February 16 2005

The article below gave the impression that former comedian Stephen Forber had written the comedy for the play and had incorporated material about CJD into his routines. Neither point is correct. Mr Forber was stand-up comedy adviser to the production and the jokes were written by Richard Stacey. We also said that some of the names of characters in the play had been changed when all of them are fictionalised.

"Have you heard the one about that mad cow disease? Me ex-wife's had it for as long as I've known her and now they reckon she's passed it on to cattle ..."

It's not the most tasteful of jokes but Stephen Forber, a former comedian on the northern club circuit, is more entitled to make it than most. Just over three years ago, his daughter, Rachel, died of Creutzfeldt-Jakob disease, the human form of BSE. He dealt with his grief partly through humour, incorporating material about CJD into his routines. But then, Stephen and Rachel had always joked about her illness: when Rachel developed jaundice as a response to her medication, Stephen called her "lemon princess". Now that nickname is the title of a play about the family's experiences, opening this week at the West Yorkshire Playhouse in Leeds.

Although some of the details within the play have been fictionalised, and some of the names changed, the story itself needed no spicing up. It featured stonewalling government agents, hovering tabloids (who paid for Rachel to receive treatment in exchange for exclusives) and an ostracised Leeds scientist dissecting cows' heads in his garage.

The first signs that something was wrong with Rachel came in early 2001, when she was 20. A bright, energetic girl who had just completed her basic training in the army, Rachel became sullen, withdrawn and difficult to live with. At first her family thought she was depressed. Then her speech started to slur and she began to lose co-ordination. In May 2001 doctors concluded that Rachel had become Britain's 103rd victim of CJD.

Rachel was given less than a year to live, but Forber refused to accept this. After scouring the internet for information, he decided to get in touch with a neurologist at the University of San Francisco. Dr Stanley Prusiner had won the Nobel prize for discovering prions, the abnormal proteins that cause BSE in cattle; now he was ready to start trials of an unlicensed drug that had previously been used for the treatment of malaria. The American government gave permission for Rachel to become the first human to be treated with Quinacrine.

Rachel arrived in the US in July 2001 barely able to walk or communicate, but after four weeks on the drug the damaged brain tissues showed signs of repair and she regained a significant degree of motor control. For a while the media speculated about a miracle cure. But Quinacrine is highly toxic to the liver, and Rachel became jaundiced. The side effects meant Rachel had to stop the treatment, and she died four weeks later, in December 2001.

Three years later, Forber feels public attitudes towards CJD sufferers have not changed. "People still don't want to talk about it," he says. "One of the hardest things we had to deal with when Rachel became ill was people treating us as if we were somehow unclean - that we were personally responsible for having dirty meat in the house."

That's why, when he was contacted by Ruth Carney of the West Yorkshire Playhouse, he was willing to do anything to help her turn Rachel's story into a play - even invite her to his home in Newton le Willows and, two weeks later, entrust this comparative stranger with his diaries. Carney developed the material in the diaries with a group of drama students, then invited Forber to attend a workshop at the National Theatre Studio. The experience proved traumatic. "Stephen was so distressed I seriously considered calling a halt to the project," Carney recalls. "But at the end he turned to me and said, 'This needs to go further.' "

Writer Rachael McGill was brought on board to shape the material, with input from Dr Stephen Dealler, the Leeds-based scientist who was one of the first experts to express fears that BSE posed a public health risk. Dealler was recruited as the scientific consultant, but he had his own story to tell: at one point he was reduced to carrying out experiments in his garage, during which time his equipment was confiscated by the Ministry of Agriculture and his home broken into and vital computer discs stolen.

The suggestion that some of Forber's club routines could be incorporated into the play was made by one of Carney's students. At first she recoiled. "I thought, 'You can't show a bloke up there, making jokes about his daughter's death.' But then I put the idea to Stephen and he was fine."

"I wasn't too sure about it at first," Forber admits. "But then, my daughter never lost her sense of humour. She and I were cracking jokes right up until the end. It's a way of dealing with your fear, I suppose."

Forber approved the final version of the script, but admits to having mixed feelings about attending the first night. "I'll probably be sat there biting my lip. But in another sense, I don't expect to recognise myself as the bloke who inspired the play at all.

"Sometimes it feels as if the past three years must have happened to someone else. So what if I went on the internet, found a famous professor and flew to America? Big deal. What did I do that any other father wouldn't have done if he thought there was the slightest chance of saving his daughter's life?"

· The Lemon Princess opens at the West Yorkshire Playhouse, Leeds, tonight. Box office: 0113-213 7700.