He and his colleague Graziella Pellegrini had tried this once before in 2006, but on a smaller scale. Back then, they successfully treated a 49-year-old woman with a large EB-induced wound on her right leg. Hassan’s condition was much worse—and he was just a child. Still, there was nothing else to try.

In August, De Luca and Pelligrini got the green light to try their technique. In September, they collected a square inch of skin from Hassan’s groin—one of the few parts of his body with intact skin. They isolated stem cells, genetically modified them, and created their gene-corrected skin grafts. In October and November, they transplanted these onto Hassan, replacing around 80 percent of his old skin.

It worked. In February 2016, Hassan was discharged from the hospital. In March, he was back in school. He needs no ointments. His skin is strong. It doesn’t even itch. “He hasn’t developed a single blister,” says de Luca, who shared the details of Hassan’s story with me. “He’s gaining weight. He’s playing sports. He’s got a normal social life.”

EB has been called “the worst disease you’ve never heard of.” In the United States, it affects around one in every 20,000 people, and the many types and subtypes are caused by mutations in at least 18 possible genes. But all of these mutations have one thing in common: They impair the molecules that strengthen skin, making it extremely fragile. For some people, the symptoms are mild, while others are afflicted with massive wounds and blisters. When it comes to junctional EB—one of the most severe types, and the one Hassan had—around 40 percent of people die before adolescence.

“Whenever I speak about EB, I find myself saying: until there is a cure ...” says Kimberly Morel, who directs an EB clinic at Columbia University. “Now it seems there is more hope on the horizon for this terrible disease.”

Hassan’s treatment is “a sea change to the world of EB,” says Brett Kopelan, the executive director of the Dystrophic Epidermolysis Bullosa Research Association of America. Even though it’s only one instance of success, “it’s made such a change in that one subject that I think it’ll be very much welcome by the EB community. You’re looking generally at a desperate patient population. I have a daughter with recessive dystrophic EB. If something like this were to be commercially viable, it’s certainly something we would pursue.”

Hassan’s miraculous recovery mirrors that of two young boys who, in 1983, accidentally set themselves on fire and burned the skin off more than 97 percent of their bodies. Their lives were saved by the physician Howard Green, who had inadvertently discovered a way of regenerating skin so it could be grafted onto burn victims. Green’s technique has since saved countless lives, and fueled the entire fields of stem-cell biology and regenerative medicine.