Epidermolysis bullosa (EB): A painful and all but incurable genetic skin disorder that affects 2 to 4 children out of 100,000.
Bone marrow transplant: A treatment, usually used for leukemia and other blood disorders, in which the patient's bone marrow is destroyed, then replaced with a donor's.
What's new: University of Minnesota doctors used bone marrow transplants to treat seven children with EB. Two died, but five improved.
The significance: It showed that cells from bone marrow can become another kind of human tissue, an advance for adult stem cell therapies.