Boy in a bubble gets leukaemia after gene therapy

A child who was born with a rare immunodeficient condition has developed leukaemia as a result of gene therapy he received at Great Ormond Street children's hospital in London.

The boy who is now three was born with rare X-linked severe combined immunodeficiency, (SCID-X1), a condition which only affects males.

It is often called the "baby in the bubble syndrome", and most victims die within their first year without treatment.

The boy was given gene therapy as a baby to save his life and he is the first child in the UK, but the fifth in Europe, to develop leukaemia as a result of the treatment.

Five years ago in Paris 4 of 11 boys given similar gene therapy also developed the disease and one has died.

When the boy started the gene therapy trial in 2005 the doctors at Great Ormond Street were aware of the leukaemia risk.

But as Professor Bobby Gaspar, a consultant immunologist working on the programme says, the benefits for such children outweigh the risks as their only other option is a bone marrow transplant.

However unless a relative is a perfect match, they also have to undergo chemotherapy, which kills up to 20% of such babies.

Professor Gaspar says they knew that this was a possible side-effect and therefore carefully counselled families before they entered the programme.

Gaspar says such risks had to be balanced against the risks of conventional treatment which contain significant hazards.

Scientists believe a vector, a modified virus introduced to the bone marrow cells to deliver a working copy of the defective gene, is the cause of the problem.

As they are unable to control where it ends up, they suspect that if it lands next to a cancer gene it can switch it on, causing cancer.

They are now planning another trial using a vector that has been modified so that even if it lands next to a cancer gene it will not switch it on.

While childhood leukemia is as a rule treatable, with cure rates of 90 percent or more, children with SCID who cannot get a bone marrow transplant almost always die within a year.