Up to half of patients who undergo a full face transplant may find that their body eventually rejects the graft, surgeons have warned.
Some may even have to have their new face removed, leaving them with even worse disfigurement than before the surgery.
And because they will have to take high doses of immunosuppressive drugs to try to prevent rejection, they will be at a massively increased risk of a range of potentially fatal cancers and other diseases.
The grim analysis came from an expert working group of the Royal College of Surgeons (RCS), which yesterday published its latest report on the highly controversial surgery.
Professor Sir Peter Morris, who chaired the RCS working group, said that full face transplants were essentially a "leap in the dark" because so little was known about the potential psychological and health impact of the process. Three years ago the same group said that it was inappropriate for full transplants to be attempted because of the huge medical, psychological and ethical issues surrounding the prospect of taking a face from a dead person and grafting it onto a living recipient.
Yesterday it said that so long as stringent criteria were met, the ethics committees of hospitals could be justified in giving the go-ahead for surgery.
Peter Butler, a consultant surgeon at the Royal Free Hospital in London, has already won permission from the ethics committee at the hospital to carry out the world's first full face transplant and is currently searching for a suitable candidate.
Skin is the most rejected transplantable tissue in the body and the RCS group estimated that between 30 and 50 per cent of face transplants could result in problems within five years.
While some rejection can be managed with drugs, patients could still lose mobility in their new face.
In extreme cases, the face may have to be removed entirely and a patient who had already gone through a catalogue of reconstructive surgery before their transplant would be back "at the bottom of the ladder", the report said. Last year a French woman, Isabelle Dinoire, underwent a partial face transplant, which has so far proved successful.
The working group has come up with 15 "minimal requirements" before a full face transplant should be approved,including the stringent counselling of potential patients.Reuse content