A Westcountry girl with serious health problems is to be one of the first people to undergo a pioneering operation – and it's been made possible thanks to her 12-year-old brother.

Fifteen-year-old Sonya Thomas is hoping she will be cured of a life-threatening disease which has seen her spend more time in hospital than at home in the last three years.

Sonya, who lives with her family in Torpoint, was diagnosed with Crohn's and colitis in 2007. She has to take the strongest drugs available and doctors in Bristol have decided to carry out a pioneering bone marrow transplant.

The doctors are trialling the surgery that will hopefully reduce the impact of the disease and Sonya will be one of the first ten people to have the treatment.

Despite the whole family being tested in June, Sonya's 12-year-old brother Terry was the only match and he has agreed to undergo an operation in the spring to give his sister a chance of recovering from the disease which attacks the bowel.

Experts at the Bristol Royal Hospital for Children have told the family that Sonya's condition is at the most severe level they have seen. At one point, the teenager had to have weekly blood transfusions.

Now each fortnight Sonya travels with her mum Helen to Bristol to get the drugs she needs to control the disease. Helen said: 'We are like two separate families because we are always in Bristol and Peter (Sonya's dad) and Terry are always in Torpoint.'

Looking ahead to the transplant, Helen said: 'It is the end of the road really – we are trying the last thing we can to help Sonya.'

It is hoped the transplant will take place in April. Following the operation, Sonya will spend three months in isolation at Great Ormond Street Hospital, London.

Sonya, who is largely restricted to a wheelchair, said: 'I don't mind having it done. It is less risk when a family member donates because relations are a better match than a donor.'

Sonya, with the help of her mum, organised a Christmas craft fair to raise awareness and money for the charity, Crohn's and Colitis UK. She raised around £100.