Two years ago, doctors at the University of Minnesota took an enormous risk by putting a little boy with a terrible skin disease through a bone marrow transplant. For that boy, Nate Liao, it worked out, and he is healthier now. Thursday, in a study published in the New England Journal of Medicine, the researchers are for the first time making public their results treating seven other children with the same genetic disease. In it, they acknowledge just how risky the procedure is: Two of the seven, including the older brother of the first patient, died as a result of the treatment. But in the others it worked -- a leap forward for a devastating and painful genetic disease for which there is no other treatment and a potentially significant advance for the use of adult stem cells.