<qa>  What is vismodegibs treatment for?This pilot clinical trial studies how well vismodegib works in treating patients with chronic graft-versus-host disease that did not respond to previous steroid treatment. Chronic graft-versus-host disease can cause a build-up of scar tissue under the skin and lead to symptoms such as sclerodermatous skin changes, dry mouth, dry eye, narrowing of the esophagus, or vaginal graft-versus-host disease. Vismodegib may work against the build-up of scar tissue and be a better treatment for chronic graft-versus-host disease caused by a hematopoietic stem cell transplant. 