The original "boy in a bubble," David Vetter, suffered from a rare disease that left his immune system completely unable to fight off any disease, forcing him to live in a sterile environment inside a large plastic bubble. After a failed bone-marrow transplant from his sister, Vetter died in 1984. But today, there's new hope. British doctors have found that gene therapy can cure children with the rare disorder. Here, a guide to this medical breakthrough:

What exactly is "bubble-boy disease"?
"Bubble boy disease" — more accurately called severe combined immunodeficiency, or SCID — results from a malfunctioning gene in the bone marrow, which produces immune cells. Because the immune system is so severely weakened, any infection or disease could result in death. The children are therefore forced to lead very sheltered, isolated lives.

What's this new treatment?
In two different studies over the past several years, 16 children with SCID were treated with gene therapy. Bone marrow taken from the children was genetically modified with a functioning form of the marrow’s disease-fighting gene. The modified bone marrow was then injected back into the children, where it began to produce healthy immune cells. This new gene therapy allowed 14 of the 16 children to maintain more normal lives in a sustained way.

Is this better than a regular bone marrow transplant?
Much better. Bone marrow transplant for SCID is a complicated procedure that requires finding an appropriate donor, usually a close blood relative. It also carries the risk of graft rejection and graft-versus-host disease, in which the newly transplanted bone marrow begins to attack the transplant recipient's body.

Is this new gene therapy a cure?
Possibly. "I used to be reluctant to say that this was a cure," says researcher Dr. Bobby Gaspar, as quoted by Britain's Daily Mail. "But ten years down the line the children are extremely well and living normal lives, so it is a cure for this condition." This treatment isn't without its risks, however: One of the children developed leukemia as a result of the gene therapy. Also, two of the 16 children with SCID did not respond to the gene therapy, for reasons that aren't yet known.

Sources: Bloomberg News, Daily Mail, Discover