Measurements of Resting Energy Expenditure in Patients With or at Risk of Developing Graft Versus Host Disease

Inclusion Criteria: * Subjects must be 7-30 years of age * Signed informed consent * One of the following three criteria must be met: * Presence of grade II or greater acute GVHD as defined by Keystone criteria * Presence of clinically extensive chronic GVHD as defined by the revised Seattle criteria * Any subject identified prior to allogeneic transplant, or following allogeneic transplant, who is at risk for acute or chronic GVHD Exclusion Criteria: * Inability to meet the requirements of the study procedures * Any subject who is receiving supplemental oxygen * Withdrawal of consent