A world-renowned musician has vowed to do everything she can to raise awareness of the rare condition her sister has just been diagnosed with.

Lesley Bayly-Bureau, 11, sister of violinist Diana Yukawa, was misdiagnosed with epilepsy for months before doctors discovered she has a rare blood sugar disorder.

Lesley's hyperinsulinism (HI), which affects one in every 35,000 babies in the UK means she must eat every two hours or risk a life-threatening seizure.

She is now being taught at home in Coombe Lane, Raynes Park, so her mother, Susanne Bayly, can make sure she does not skip any snacks.

Diana said: "The scary thing is how many of these children have this disorder, but have been misdiagnosed with epilepsy.

"Lesley was regularly seeing a paediatrician and mummy was saying to them she has these strange symptoms when she doesn't eat.

"We could see that food was making the world of difference. Instinctively we could see that it wasn't a neurological thing."

Lesley has had problems with her health for most of her life, having been diagnosed with an underactive thyroid gland when she was seven.

She had her first seizure in December 2003, minutes after leaving a check-up appointment with a paediatrician.

Diana, 19, said: "I got a terrible phone call from mummy saying that she had collapsed and she had fainted.

"It was completely terrifying. I was just so scared and I got a cab and I went to the hospital.

"I gave her a Polo and she began to come round."

Doctors at Great Ormond Street Hospital believe she may be the first child to be diagnosed with an even rarer form of HI when genetic tests come back from Cambridge in eight weeks' time.

Susanne said: "If the results prove that she is the first child who has this disorder, Lesley will be opening the door to other children who are being misdiagnosed.

"One of the paediatric nurses at the hospital said that new-born children with HI are sent home twitching, and the brain damage has already occurred.

"There is also a link with cot death now."

The family has now teamed up with the Children's Hyperinsulinism Fund to raise money for a HI research unit at Great Ormond Street Hospital.

Diana is also planning to hold a fundraising concert to raise awareness, and is contacting other big names in the classical music world asking them to lend their support.

Their main goal is to raise awareness, as a cure for Lesley is unlikely to be found in the immediate future.

Meanwhile, Lesley is relieved that she now knows how to control her condition, and is looking forward to proving children who made fun of her wrong.

She said: "I don't have to worry about it now.

"I am able to tell them what I have and they will realise that they were wrong."

For more information, or to make a donation, visit the Children's Hyperinsulinism Fund's website at www.hi-fund.org or telephone 01376 528 569.

jbowring@london.newsquest.co.uk