Risk factors for infectioninclude the degree and duration of neutropenia; profoundpan-immunosuppression; disruption of mucosal barrier by radiochemotherapy;HLA mismatch; central venous access; donor prior exposures; and especiallycord blood transplants. Inadequate immunoglobulin (especially IgG2 and IgG4)production increases risk of infection with encapsulated organisms despitetotal Ig levels in the normal range after transplant.

Please see Chapter 22 forspecific pulmonary infections.

General time frames of when infection is likely to occur

Figure 18.1 outlines theperiod of major host dei cits and infections that occur during allogeneicHSCT in relation to the deployment of targeted pathogen-specii cprophylactic, preemptive, and empiric therapies. Risk for infectiouscomplications is temporally dependent, and it may be signii cantly decreasedby prophylactic, preemptive, or empiric therapy. The risk of certaininfections after transplantation is highly associated with ongoingimmunologic manipulation as seen with the therapy for GVHD (Figure 18.1;linkages denoted by vertical arrows).