After losing 80 percent of his skin to a devastating genetic disease, a seven-year-old boy underwent an experimental treatment replacing his epidermis with new skin grown in a lab from genetically modified stem cells. Two years on from the dramatic surgery the boy is alive, well, and back at school.

Referred to as a "butterfly child," because of the fragility of his skin, the boy suffers from a rare and incurable skin disease called epidermolysis bullosa. The disease is caused by mutations in genes responsible for skin regeneration and result in skin that is very easily blistered or wounded.

In June 2015, the boy was admitted into hospital with approximately 60 percent of his skin lost. He was suffering from sepsis, had a high fever, and all traditional therapies had failed. The only option was a new experimental therapy.

The process started with the researchers taking a skin biopsy from the boy to obtain epidermal stem cells. These stem cells were genetically modified to correct the mutation causing the disease. The modified stem cells were then grown into transgenic skin transplants.

In October the boy underwent the first transplantation and his condition swiftly improved. Over following months several more transplants were carried out across his entire body.

"Overall, 0.94 square meters of transgenic epidermis were transplanted onto the young patient in order to cover all defects, accounting for 80 percent of his entire body surface," explains Dr Tobias Hirsch, one of the doctors involved in the therapy.

By February 2016 all the transplants had been completed, and the boy was discharged. The genetically modified skin had successfully formed a new epidermis, with healthy strong skin that is now showing signs of early hair formation.

This remarkable case is the largest transplantation of transgenic skin ever undertaken in the world. It's a magnificent example of cutting-edge medical therapies being successfully deployed to save lives that just a few short years ago would have easily been lost.

The study was published in the journal Nature.