Pearl Porter, 20, from Weymouth is fundraising for sister Ruby Mai Porter, 18, who suffers from a rare brain disease, to have a memorable Christmas

Eighteen-year-old Ruby Mai Porter, from Weymouth, suffers from an extremely rare, incurable neurological disorder that doctors have been unable to identify.

As her condition deteriorates and her future is uncertain, her sister, Pearl, 20, has launched a £2,500 fundraising campaign to help the family have Christmas to remember.

Mum, Michelle Clements, 42, of Shrubbery Lane Weymouth, said: "Ruby’s condition has got drastically worse over the last four or five months, and there is no way of knowing how long we have.

"Ruby loves Christmas and we are hoping to fundraise to bring it to her early this year. We are thinking of having a sleigh ride with reindeers and decorating the outside of the house with lights."

After a life-long struggle with epilepsy, which caused her to have 15 fits on a daily basis, Ruby was finally diagnosed in December last year.

Throughout her life, Ruby has suffered with seizures and has undergone numerous lumber punctures and muscle biopsies to determine the cause.

Now, doctors have said it is most likely Ruby was born with the terminal disorder, which is so rare that there is no medical term for it.

Michelle said: "Before Ruby’s condition deteriorated, she was a keen athlete. She used to swim like a fish and run for her school. She wanted to become a boxer or a wrestler."

As the illness has manifested itself in recent months Ruby has become wheelchair bound and lost the functions in the right side of her body.

She now requires 24 hour medication and doctors say there is only a one per cent chance medication will work.

Appealing for donations on the Just Giving site, Pearl said: "Time is not on our side, Ruby is slowly losing her battle to this illness.

"There are a few more things we would like to do with her as a family, but need help with funding. She is such an amazing, brave and inspirational girl."

For Michelle, the decision to fundraise publicly was not an easy one but she has been encouraged by the thought of creating special memories for Ruby, Pearl and little sister, Sapphire, which she would otherwise not be able to afford.

Michelle said:"She has changed so much that it is hard to recognise the little girl she once was, but I can see that Ruby is still in there. My life is now one big worry. Thankfully Ruby has an amazing sister in Pearl, I wouldn’t be able to manage without her, and her Step Dad Andy."

To donate go to www.justgiving.com/crowdfunding/pearl-porter-1