Topical Ruxolitinib for Cutaneous Chronic Graft Versus Host Disease (cGVHD)

Background: About half the people who have a hematopoietic stem cell transplant using donor cells get Chronic Graft Versus Host Disease (cGVHD). This is chronic graft versus host disease. Immune cells from the donor may see the body tissues in the person as foreign and attack, causing damage. The skin is the most commonly affected organ. Most cGVHD therapies have serious side effects. The cream ruxolitinib inhibits proteins that may play a role in cGVHD. Objective: To test the safety and effectiveness of topical ruxolitinib 1.5 percent cream in people with cGVHD of the skin. Eligibility: People ages 12 and older with epidermal skin cGVHD Design: Participants will be screened with: Medical history Physical exam Blood and urine tests Skin sample taken (biopsy) to confirm the diagnosis. At the baseline visit, participants will have: Skin disease measured with rulers, photographs, and tracing the outline of skin lesions To complete questionnaires about their symptoms Blood and urine tests Some participants will also have a skin biopsy, or total body photographs while they wear only underwear. Participants will get the ruxolitinib cream and a placebo cream to apply to 2 separate areas of disease. They will do this twice a day for 6 weeks, if they do not have serious side effects. Neither the study team nor the participant will know which area will get ruxolitinib cream and the placebo cream. Participants will write down: * When they apply the creams * Any side effects * Any medications they take Most participants will have 4 visits during the 6 weeks they use the creams. Some will have 3 visits and a phone call to see how they are doing. All participants will get a call 4-6 weeks after they stop. Visits include physical exams, blood tests, skin disease measurements, questionnaires, and photos.