Doctors in Europe used gene therapy to grow sheets of healthy skin that saved the life of a boy with a genetic disease that had destroyed most of his skin, the team reported on Wednesday in the journal Nature.

This was not the first use of the treatment, which adds gene therapy to a technique developed to grow skin grafts for burn victims. But it was by far the most body surface ever covered in a patient with a genetic disorder: nine square feet.

The boy’s disease, junctional epidermolysis bullosa, causes extremely fragile skin that blisters and tears, and is prone to infections and skin cancer. He had been expected to die but has recovered. Two years after the treatment, he continues to have healthy skin and lead a normal life. A video provided by the medical team shows the boy, Hassan, playing soccer with his father. According to news reports, the family is originally from Syria.

Epidermolysis bullosa (epi-derm-uh-LY-sis bull-OH-suh) takes various forms, depending on the genetic mutation involved. About 25,000 people in the United States have the condition, and 500,000 worldwide. The severity varies, but some patients spend much of their lives covered in bandages and in severe pain.