The spectrum of potential pathogens known to cause pulmonary infections in immunocompromised individuals has grown as a result of intensified immunosuppression, prolonged patient survival, the emergence of antimicrobial-resistant pathogens, and improved diagnostic assays. Immunocompromised hosts are defined by susceptibility to infection with organisms of little native virulence in normal individuals. Each group of hosts (eg, AIDS, solid organ transplant recipients, or hematopoietic cell transplant recipients) has enhanced susceptibility to a subset of pathogens depending upon the nature of the underlying immune defects. The impact of antibody-based therapies against T and B lymphocytes and tumor necrosis factor-alpha should be considered in the assessment of risk.
Survival has improved with the availability of newer antimicrobial agents, including azole antifungals, macrolides, antivirals, and antiretroviral drugs. Despite these advances, pulmonary infection remains the most common form of documented tissue invasive infection observed in these hosts [1-5].
Common pulmonary infections in the immunocompromised host will be reviewed here. The risk of pneumonia and approaches to the evaluation and diagnosis of pulmonary infiltrates in the immunocompromised individual and the treatment of specific disease entities are discussed separately. (See "Approach to the immunocompromised patient with fever and pulmonary infiltrates".)
Infectious risks associated with specific immunomodulating agents are discussed separately. (See "Tumor necrosis factor-alpha inhibitors and mycobacterial infections" and "Tumor necrosis factor-alpha inhibitors: Risk of bacterial, viral, and fungal infections" and "Secondary immunodeficiency induced by drugs and biologics".)
A number of general considerations apply in the immunocompromised patient with a pulmonary infection: