INTRODUCTION

Several risk factors were found to be associated with the incidence and severity of chronic graft versus host disease (cGVHD) after allogeneic stem-cell transplantation (allo-SCT). The most important factor is likely to be the development of significant acute GVHD; but other classical risk factors including older age, a female donor (especially to a male patient), or some diagnoses such as chronic myeloid leukemia (CML) or aplastic anemia, were also reported. Some unique clinical situations such as the use of mismatched or unrelated donors (URDs) may be also associated with a higher risk of cGVHD, likely because of an increased reactivity between donor immune effectors and host cells. In the last decade, exploring cGVHD has also gained in importance, as more transplant centers are increasingly using allogeneic granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSC). The latter has been associated with an increased incidence of cGVHD in most studies of human leukocyte antigen (HLA)-matched sibling transplantation. More recently, the use of the so-called reduced intensity or nonmyeloablative conditioning (RIC) regimens with or without systematic donor leukocyte infusion (DLI) also showed that cGVHD is still a major limitation. Similarly, the natural history of cGVHD appears to be modified after cord blood transplantation, and will need to be closely monitored. The aim of this chapter is to address the clinical, biological, and therapeutic features of cGVHD in the specific context of the above-mentioned unique clinical situations.