The news that Chancellor Gordon Brown's four-month-old son, Fraser, has cystic fibrosis has raised the profile of this little-known disease. Health Editor Barry Nelson investigates.

IF you passed Sheryl Stephenson in the street you would never guess that she has one of the UK's most common life-threatening diseases. Seventeen-year-old Sheryl, from Crook, County Durham, is one of around 350 children and young people living with cystic fibrosis in the North-East.

The cheerful teenager, who is currently studying for three A-levels at Durham Sixth Form College, loves hanging out with her friends and working out at the gym. A few weeks ago she took part in the Great North Run, raising £2,500 to help the Cystic Fibrosis Trust find a cure.

But like every other CF sufferer Sheryl's life depends on a cocktail of drugs she takes every day to protect her from infections and to allow her to digest her food properly.

Until 2000, Sheryl had to endure two lengthy bouts of physiotherapy at the hands of her loving parents, Julia and John Stephenson. But advances in treatment mean that she can get by without physiotherapy.

Instead of a good pummelling - designed to help her body get rid of the sticky mucus which clogs the lungs and digestive system of CF sufferers - Sheryl has been able to rely on a device which involves blowing into a face mask twice a day for 20 minutes.

"It's a lot better," she says. "I have to do this in the morning and last thing at night. The physio used to take 21 minutes twice a day."

In calm, matter-of-fact tones, Sheryl explains how she also has to use a nebuliser to inhale medication for two, six minute bursts twice a day. And then she tells you how doctors implanted a small metal and rubber disk just under the skin in her chest which allows easy access for the regular intravenous drugs she needs to take.

"They had to do this because they had put drips into my arms so many times that all the veins had collapsed," she says.

Sheryl, who is hoping to study forensic science at Teesside University, says she's saddened to hear that Chancellor Gordon Brown's four-month-old son, Fraser, has been diagnosed with CF, but she welcomes the extra publicity this will generate for the condition.

"Not many people know what it is. When I was born my parents didn't have a clue what it was," says Sheryl.

She is full of admiration for the way her parents have cared for her since she was a baby. "My mam and dad were taught how to do the physiotherapy and they did it twice a day for years. They and my brother, Shaun, are fantastic. When you have CF you need as much support as you can get."

Durham City couple, Geoff and Phillippa Turner, says their hearts also go out to the Browns.

Since their daughter, Neve, was diagnosed with CF in August 2005 - followed by her sister Drew - the couple have had to give their daughters daily bouts of physiotherapy to keep their lungs clear and take them on regular trips to the regional CF centre at the Royal Victoria Infirmary, in Newcastle.

The couple got in touch with the North-East branch of the Cystic Fibrosis Trust and benefited from specialist advice and support.

When they heard a calendar was being produced to help raise funds to find a cure they quickly sent their daughters' photographs for possible inclusion. And they were thrilled when the trust decided to feature the two sisters in two months of their calendar.

This year Neve, five, and Drew, three, were December and November calendar girls respectively and next year the sisters will be pictured together on the August page.

The Chancellor and his wife, Sarah, also have the sympathy of Lucinda and Guy Fleming-Jones from Old Cassop, near Durham City.

Lucinda had a perfectly normal pregnancy and was looking forward to a healthy baby. "But we knew there was a problem when Dylan was born because his stomach was swollen," she says. He was taken away for tests and needed surgery for a blockage. He spent the first three months of his life in hospital.

Dylan is now five and his parents have been taught to do the necessary physiotherapy twice a day.

"Every day Dylan has a variety of drugs, he swallows about 40 tablets, including massive ones. He doesn't think it is odd because it is what he is used to," says Lucinda.

While she is happy to do everything she can to make her son more comfortable, she remains worried about the long-term outlook. "You can cope with the treatments and the hospital visits but it is hard to think about the fact that this is still a life-limiting disease. They are so close to finding new treatments but they need more funding to speed things up"

Lucinda and Guy can only remain positive and hope that the Brown family's misfortune might help to raise awareness about CF and persuade more people to donate funds.

"We go through an amazing routine every day. You have to pat him on the back and tip him upside down. There is no let up, even on Christmas Day we will be doing this," says Lucinda, who now has a one-year-old little girl, Ella, who is clear of CF.

"You just have to get on with it and hope the research pays off," she adds.