Leading article: Good genes

Gene therapy promises much, but real breakthroughs have so far been few and far between. Today, though, we have a glimpse of what the future might hold. An Aids patient also suffering from leukaemia was given a transplant at a Berlin hospital with bone marrow from someone with a genetic resistance to HIV. The man, who had taken antiretroviral drugs for a decade, has now been free of HIV for two years.

Doctors are, quite reasonably, cautious. They warn that the HIV could return. Bone-marrow transplants hold dangers of their own, and finding donors is not easy. But the longer the man survives without antiretroviral drugs, the more hopes such pioneering treatment will inspire. A one-off operation that would replace a lifetime on drugs could be preferable to many people – and to cash-strapped health services. Although treatments developed from bone-marrow transplants are not cheap, the operation has already paid for itself in terms of the drugs saved.