Infectious complications

Infections are the most frequently occurring complications of hematopoietic stem cell transplantation (HSCT). Myelosuppressive medications, the conditioning regimen (chemotherapy, radiation therapy), mucosal damage, type of transplant, immune-suppressive therapy, and graft-versus-host disease (GvHD) all predispose the HSCT patient to life-threatening infections. Abnormal B- and T-lymphocyte function results in impaired cellular and humoral immune function. Infections that can occur in the setting of impaired cellular immunity include fungal, protozoal, and viral diseases. Humoral defects can predispose a patient to infection with pyogenic organisms and other bacteria as well as viral infections. Patients are also often hypogammaglobulinemic following transplant. Neutrophil function is impaired by the use of corticosteroids and other medications. Functional asplenia is common. The occurrence of infections in an individual patient varies due to underlying disease and immunosuppression, endogenous host flora, and pretreatment infections. Infections also vary according to the phase of the transplant process.