She knows she needs a bone marrow transplant and keeps asking when she will have one

Catherine's mother

"I also noticed that she was covered with bruises, and when we brushed her teeth, her gums were bleeding - at first I thought it was leukaemia," Catherine's mother said.

She was diagnosed with Fanconi anaemia, which is so rare that only 10 children a year in the UK are born with it.

The Anthony Nolan trust has checked worldwide registers to find a match for her, but so far nothing suitable has been found.

If a matching donor is found, Catherine will be able to live a fairly normal life.

More than 300 people came to the clinic in Narborough, Leicestershire last week, and some had to be turned away, a trust spokeswoman said.

"She knows she is a poorly child and she knows she needs a bone marrow transplant and keeps asking when she will have one," her mother said.

Donors must be between 18 and 40 years old, in good health and willing to give a blood sample at the clinic.

Participants are placed on a register, and will be asked to donate if a match is found, but are given the option to withdraw at any stage.

The trust has 316,000 bone marrow donors registered in the UK, with five million people on registers worldwide.