Infections in Recipients of Hematopoietic Stem Cell Transplants

Infectious complications of hematopoietic stem cell transplantation (HSCT) are quite common and can be associated with high morbidity/mortality in these vulnerable populations. Therefore it is essential for infectious disease providers and transplantation physicians to have significant knowledge on these infections and to work together in managing these patients. In this chapter we describe the complexity of these individuals and their infectious complications. To accomplish this we start with an outline of basic HSCT techniques. This is followed by clinical syndromes, host defense defects at different time points after various transplantations, the factors affecting immune reconstitution after HSCTs, and the natural history of individual infections in this population. The type of microbiologic agent and the severity of infection depend upon multiple factors, including the pretransplantation exposure history (e.g., viral serostatus), donor source (e.g., allogeneic or autologous), intensity of chemotherapy/radiation therapy used before transplantation (e.g., myeloablative or reduced-intensity conditioning), and the number of days after the transplantation. To complicate the matter more, many posttransplantation complications mimic infectious processes, and multiple infections may concurrently occur in the same patient (e.g., graft-versus-host disease and infections). Therefore a patient suspected of having an infectious disease requires a careful review of history, starting from pretransplantation infections, serologic profiles to document infection latency, and transplantation characteristics, to current data, including available culture data and contemporaneous transplantation complications.