The four-year-old had been fighting the rare Niemann-Pick Disease Type C since she was just five weeks old.

Her parents Toni, 38, and Stewart, 37, were unaware they each carry a gene which causes the disease, and were told by doctors there was a one-in-250,000 chance that two people with the gene would meet and have a child.

The condition affects just 300 people worldwide.

Toni, of Fatfield, Washington, said: "We always knew she would have a short life, but with this disease no one can tell you when or how.

"It has been a roller coaster. She would be all right, and then she wouldn't. Last weekend, when she became poorly again, unfortunately her little body couldn't fight any longer."

Lucy was born at Sunderland Royal Hospital on May 27, 2003, with a spleen 11 times bigger than normal, an enlarged liver and jaundice.

As the disease progressed, she lost mobility and the ability to swallow and had to be fed through a tube. She was unable to talk properly and could only say three words, one of which was her 15-year-old brother's name, Jake.

But despite her problems Lucy will be remembered as a happy child with a wicked sense of humour, who touched everyone she came into contact with.

Toni, who has worked full time for the Niemann-Pick Disease Group for the past two years, said: "She had a beautiful, bright smile and she made such a difference to everyone's lives. Everyone she met loved her.

"She was our little ray of sunshine. The name Lucy means light and that's what she was, the light of our lives.

"She brought us so much joy and made a huge difference to our lives."
Lucy passed away at home on Saturday, surrounded by her family.

Her funeral will be held at Sunderland Crematorium tomorrow at 12.30pm. Those attending are asked to wear an item of pink clothing (a scarf or a tie) – Lucy's favourite colour – in celebration of her life.

Donations, if desired, should be made in lieu of flowers to Niemann-Pick Disease Group, c/o Walker and Morrell Funeral Directors, 4 West View, Concord, Washington, NE37 2DT, tel. 416 4160.