A relatively new technique that is still being explored and perfected, gene therapy is used to treat genetic conditions which have in the past proven difficult to cure.

The first use of gene therapy was to tackle severe combined immunodeficiency, a very rare disease in a young girl in the US in 1990. The treatment helped boost her immune system, meaning minor infections that are usually life threatening among patients that suffer from the disease were more easily fended off.

Some cancers, including melanoma, can also now be treated using similar methods. Gene therapy has been applied, mostly in trials, to combat other genetic diseases and it is hoped it will one day help combat cystic fibrosis, hemophilia and sickle cell disease. Retinal disease is another promising possibility.

Procedure information
Gene therapy usually involves the introduction of a healthy part of the human genome into the patient to replace a faulty gene. This transfer is often conducted by altering a virus genetically to become a carrier of the replacement gene, which is then introduced into the body at the sight of the disease, perhaps the lungs or the liver. The genetic material is then unloaded and incorporated into the genome.

Two broadly different methods are used. The first, ex vivo, means cells are repaired outside the body and then reintroduced, while in vivo takes place by introducing the new gene component inside the body.

Recovery time
The period needed to get over a course of gene therapy varies greatly depending on the condition. Some patients require repeated gene therapy to live with a particular condition, as is the case with severe combined immunodeficiency. Certain cases in which stem cells have been used in the treatment have required additional gene therapy after 4 years, although cases vary not least because of advances in the application of the treatment.