Natural History Study of Clinical and Biological Factors Determining Outcomes in Chronic Graft-Versus-Host Disease

* INCLUSION CRITERIA: 1. Any patient age 1 and older referred by the primary transplant physician for the evaluation of chronic graft-versus-host disease independently of age or underlying diagnosis 2. Patient or the patient's legal representative is able and willing to provide consent. EXCLUSION CRITERIA: 1. Significant medical condition or any other significant circumstance that could in the PIs assessment affect the patient's ability to tolerate, comply, or complete the study 2. Patients who in the PIs assessment have a life expectancy \<3 months. Note: Because it is not always possible to make a clear clinical distinction between acute and chronic GVHD, patients with acute GVHD are not a-priori excluded until the possibility of chronic GVHD is reliably excluded on the basis of the clinical assessments in the cGVHD clinic. 3. Pregnant women are excluded from this study because multiple tests would need to be excluded for safety of the patient and the fetus. Inclusion Criteria for control subjects without cGVHD: * Age 1 and older * Patient has undergone Allo-HSCT * Patient or the patient's parent/guardian is able and willing to provide consent Exclusion Criteria for control subjects without cGVHD: * Active GVHD * In the previous three months have received systemic immunosuppressant therapy for the treatment of GVHD * In the previous three months have received therapy for malignancy