A group of European researchers used stem cell therapy to grow replacement skin for a seven-year-old boy, potentially opening the door to a new class of stem cell treatments in the future.

Since birth, the young patient had suffered skin lesions and blisters as a result of a serious, sometimes-fatal genetic condition called junctional epidermolysis bullosa (JEB), according to an article published Wednesday in the journal Nature. By 2015, when he was seven, the boy was down to roughly 40% of his skin, and was in a medically induced coma at Children’s Hospital in Bochum, Germany, according to a Nature podcast accompanying the article. A cure seemed unlikely — until, that is, his care team contacted Dr. Michele De Luca, of the Center for Regenerative Medicine at Italy’s University of Modena.

De Luca decided to try a radical and largely untested strategy: a skin transplant using genetically modified stem cells. It was risky, but it was the only option.

Using a biopsy of the boy’s little remaining healthy skin, De Luca’s team cloned skin cells that matched his natural cells, but were genetically modified to eliminate the mutation that led to his JEB diagnosis, according to Nature. They used these genetically modified cells to grow fresh skin, which was sent back to Germany and transplanted onto the patient in a series of three surgeries. Two years later, the child’s epidermis is “fully functional” and he “is behaving as a normal boy,” De Luca said in the podcast.

While it’s too early to say whether such a treatment would ever be feasible on a larger scale — and whether it will remain effective for the rest of the child’s life — researchers are encouraged by its early success, and wrote that it could lead to other innovative uses for stem cell and gene therapy in the future. “This study,” they said, “provides a blueprint that can be applied to other stem cell-mediated combined ex vivo [outside the body] cell and gene therapies.”

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Write to Jamie Ducharme at jamie.ducharme@time.com.