The purpose of this research study is to evaluate the safety and feasibility of extracorporeal photopheresis (ECP) in the treatment of steroid-refractory acute graft-versus-host disease (GVHD) in children.

Inclusion Criteria:

• Status-post allogeneic stem cell transplant (includes cord blood transplant, matched-unrelated-donor transplant and matched-related donor transplant) for any indication.
• HLA matching needs to be 4-6/6 by at least intermediate resolution for class I + II for cord blood and 5-6/6 for matched related or matched unrelated donors.
• Diagnosis of grade II-IV acute GVHD with histological confirmation of at least one organ (skin, gut, or liver) within the last 14 days. Grading of acute GVHD is per the standard Keystone criteria. Prior to enrollment, efforts should be made to rule out diagnoses that may mimic GVHD, such as drug rashes or GI infection. Patients that are being treated for acute GVHD and appear to be progressing to chronic GVHD are also eligible
• No improvement, or worsening, of acute GVHD after at least 4 days of IV methylprednisolone dosed at, at least 2.0mg/kg/day..
• Weight >25.0kg.
• Adequate venous access.

Exclusion Criteria:

• Evidence of veno-occlusive disease.
• Intubated patient.
• Patient receiving dialysis.
• Age > 30.
• Total bilirubin >15mg/dL