SYDNEY: An Australian girl has spontaneously switched blood groups and adopted her donor's immune system following a liver transplant, in the first known case of its type.

Demi-Lee Brennan was aged nine and seriously ill with liver failure when she received the transplant, said doctors at a top Sydney children's hospital.

Nine months later it was discovered that she had changed blood types and her immune system had switched over to that of the donor after stem cells from the new liver migrated to her bone marrow.

She is now a healthy 15-year-old, said Michael Stormon, a hepatologist treating her. Stormon said he had given several presentations on the case around the world and had heard of none like it.

Never seen before

"It is extremely unusual – in fact we don't know of any other instance in which this happened," he said. "In effect she had had a bone marrow transplant. The majority of her immune system had also switched over to that of the donor."

An article on the case was published in Thursday's edition of the leading U.S. medical journal The New England Journal of Medicine.

Doctors who treated Brennan say she is now only under treatment as an outpatient and are interested to know if the case could have other applications in transplant surgery, where rejection of donor organs by the recipient's immune system is a major hurdle.

Stormon said it appeared that Brennan may have been fortunate because a "sequence of serendipitous events", including a post-transplantation infection, may have given the stem cells from her donor's liver the chance to proliferate.

The task now was to establish whether the same sort of outcome could be replicated in other transplant patients, he said.