Leann Thompson (32) and her husband Dean (39), of Station Road, are parents to 14-month-old twins Lydia and Ella, who both have Tay-Sachs disease, and Jessica (3).

The twin sisters were diagnosed with the terminal illness when they were seven months old.

The condition means that harmful quantities of a fatty substance build up in tissues and nerve cells in the brain.

Although infants who have the disease appear to develop normally during the first few months of their life, their mental and physical abilities deteriorate.

Leann said: “Lydia had a slight squint so we found out when we had it checked. It worsens as time goes on.”

There is no cure for it and even with the best care, children with the disease usually die from recurring infection by the time they are four years old.

Leann has given up work and gives full-time care to her ill daughters.

She said: “They will lose their sight and hearing and will never be able to talk normally.

“They are on a drugs trial and hopefully this will help slow the disease down. They have been on it for about six weeks now. We are trying to give them the best chance we can. They are also undergoing physiotherapy too.”

The twins are receiving treatment from Addenbrooke's Hospital in Cambridge.

Joan Thompson, of Saxon Way, Bourne, lives in hope for her granddaughters. She said: “The drug treatment will hopefully give them a better quality of life and help them to live longer.”

Leann’s mum Stella Hart, of Meadowgate, Bourne, has also given up work to help look after the tots.

She said: “You are so helpless. You just have to love them.”

The twins’ parents also became aware that they are both carriers of the disease and Leann added: “Every child we have has a one in four chance of having this.”

Special equipment is needed to help make the twins’ lives easier.

Leann said: “We are looking at converting our garage and getting a special bath for them.

“We might get a grant for that but we are not sure it will cover the cost.

“In time they will need special pushchairs. They already have some hydraulic high chairs coming because they cannot sit up in a normal one.”

Family, friends and work colleagues have rallied round on behalf of the twins, including two of their cousins Shaun (23) and Lee Dennis (21), of Bourne, who completed a bungee jump and raised £1,547 towards Lydia and Ella’s Fund.

Shaun, of Southfields, said: “You just feel so helpless. We did it to try and help make life easier.”

Leanne said: “It was thoughtful of them.

“It is nice that people want to help us.”