The NHS will fund gene therapy for the first time, with a £500,000 treatment for “bubble baby syndrome”.

Three babies are born each year with an immune defiency condition which leave them at constant risk of developing life-threatening infections.

If left untreated, infants need to be kept isolated from the outside world, which is why the condition is known as “bubble baby syndrome” and usually die before school age.

Quality of life is affected by developmental delay, chronic diarrhoea, failure to thrive and recurrent infections.

The current treatment for the condition is a stem cell transplant, which can restore the immune system if successful. However, closely matched stem cell donors are hard to find, and transplants can fail, and carry a risk of death or complications.

Today the National Institute for Health and Care Excellence (Nice) said the NHS should fund the gene therapy Strimvelis made by GlaxoSmithKline.

The treatment is so rare that it is only offered by one hospital in the world, in Italy.

The new plans - now open to public consultation - mean children would be flown to Milan to undergo the one-off treatment.

Strimvelis is only the second gene therapy for an inherited disease to be licensed anywhere in the world. The draft guidance, which is  the first time NICE has applied its new cost effectiveness limits for treatments for very rare conditions,  recommends the treatment when no suitable matched related stem cell donor is available.

Severe combined immunodeficiency due to adenosine deaminase deficiency, or ADA-SCID, is an inherited genetic condition. It affects the body’s white blood cells, leaving people with the condition without a properly functioning immune system and therefore with a high risk of developing life-threatening, recurrent infections.