SYDNEY, Jan. 24 (Kyodo) — A young Australian liver transplant patient has made medical history as her blood type has spontaneously changed to match that of her donor.

The case, published Thursday in the New England Journal of Medicine, marks the first time for a transplant patient to completely accept a donated organ to the extent where the immune system entirely changes, Australian media reported.

Demi-Lee Brennan, now 15, had an urgent liver transplant at the age of 9 after suffering acute liver failure.

Doctors at the Children's Hospital at Westmead, located in Sydney, were later stunned to find that the teenager's blood type has since changed to that of her deceased male donor.

Micheal Stormon, a gastroenterologist at the hospital, told the media that tests showed that stem cells that were transplanted with the donated liver somehow penetrated into Brennan's bone marrow, completely replacing it.

More surprisingly, he said, the girl's immune system has almost been totally replaced by that of the donor, meaning she no longer has to take drugs to thwart the body's rejection of the donated organ.

''We were stunned, absolutely stunned, and also very puzzled,'' Stormon told the Australian Associated Press. ''Even going through the literature and seeking advice internationally, we weren't able to find any other cases like it.''

Transplant patients are generally forced to take immunosuppressant drugs for life, which can have serious side effects.

Doctors are investigating the phenomenon, trying to find out how it happened and if it can be replicated, though Stormon doubted that in comments he made to the Australian Broadcasting Corp.

''It's definitely a one-off,'' Stormon said. ''This was a very serendipitous event.''

The case was revealed amid reports of a breakthrough in the United States in which scientists there have developed a new transplant technique in which kidney recipients may not need a lifetime of immunosuppressive drugs.