A nine year old girl from Norfolk has had a life-saving transplant from a so-called saviour sibling.
Megan Matthews would have died but for tissue donated by her baby brother Max. It's the first time that the entire treatment has been successfully conducted in the UK.
Megan was born with Fanconi Anaemia, a rare inherited condition which can cause bone marrow failure.
Her body could not make blood and she needed transfusions every few weeks.
She was also unable to fight infections.
A worldwide search for a suitable bone marrow donor failed.
Megan's parents, Katie and Andy from King's Lynn, said they always wanted another baby, but natural conception would have given then just a one in four chance of having a child that was a perfect tissue match.
There was also a risk that the baby would have carried the same genetic disorder as Megan.
Gift of life
Medical teams in Cambridge, Bristol and Nottingham coordinated treatment to create a baby who was a perfect tissue match and then to use donated cells to treat Megan's blood disorder.
CARE Fertility in Nottingham carried out IVF treatment, taking cells from the three day old embryos and testing each one for the disease and also checking if it was a suitable match for the transplant.
Two embryos were implanted and a single baby boy, Max, was born 18 months ago.
Max's umbilical cord blood was preserved and he later needed an operation to recover bone marrow.
The cells were used in Megan's transplant in July which was carried out at the Bristol Royal Hospital for Sick Children.
She used to require blood transfusions every three weeks and was unable to fight infections. Since the transplant, Megan has not required any blood products and now attends Addenbrookes hospital in Cambridge for a weekly check-up.
Dr Mike Gattens, a paediatric haematologist said: "This has transformed Megan's life.
"Before she was a sickly child needing lots of medical attention - over the next few months and years I hope we will see less and less of her.
"She is a very active child and I hope she can just get on and enjoy her life."
Megan's mother Katie said: "This time last year Megan had been hospitalised for eight weeks and this year we are looking forward to Christmas.
"We are looking forward without dreading if we will be in hospital or not."
Saviour sibling treatment has been used before. In 2003 Charlie Whitaker, who had a rare blood disorder, was successfully treated after a transplant of cells from his brother.
But the family had to go to the US for treatment. The technology was later approved by the UK's Human Fertilisation and Embryology Authority, on a case by case basis.
But this is the first time that the entire procedure has been successful here.
Simon Fishel, managing director of Care Fertility, said: "This is fantastic and positive medial science.
"The ethical issues are in favour of doing this work. We are trying to save the life of a child and achieve a family without the enormous burden of a child with this disorder who would die."
But Josephine Quintavalle, Director of Comment on Reproductive Ethics said of Max: "He owes his life to his capacity to be of therapeutic use to his sick sister, otherwise he would not have been chosen in the first place.
"This is the big ethical problem."
Kate Matthews said: "Max is loved for being him and not for what he has done. He has completed our family and now I have a bubbly and healthy girl."
Megan's genetic disorder, Fanconi Anaemia, means that she may face long-term health problems. But her family say they will face those hurdles when and if they come to them.