Hematopoietic stem cell transplantation: an overview of infection risks and epidemiology.

Hematopoietic stem cell transplantation (HSCT) is a treatment for multiple medical conditions that result in bone marrow failure and as an antineoplastic adoptive immunotherapy for hematologic malignancies. HSCT is associated with profound compromises in host barriers and all arms of innate and acquired immunity. The degree of immune compromise varies by type of transplant and over time. Immune reconstitution occurs within several months after autologous HSCT but takes up to a year or longer after allogeneic HSCT. In those patients who develop chronic graft-versus-host disease, immune reconstitution may take years or may never completely develop. Over time, with strengthening immune reconstitution and control of graft-versus-host disease, the risk for infection dissipates.